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Understanding and improving the biological targeting of soil insecticides
Reed, Joseph Peter, Ph.D.
The Ohio State University, 1989
UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106 PLEASE NOTE:
Duplicate page number(s); text follows. Filmed as received.
152-182
UMI UNDERSTANDING AND IMPROVING THE BIOLOGICAL
TARGETING OF SOIL INSECTICIDES
DISSERTATION
Presented in Partial Fulfillment of the Requirements for
the Degree of Doctor of Philosophy in the Graduate School of
The Ohio State University
By
Joseph Peter Reed, B.S., M.S.
*****
The Ohio State University
1989
Dissertation Committee: Approved by
F. R. Hall
H. R. Krueger
H. R. Willson
D. L. Reichard Adviser Department of Entomology DEDICATION
This dissertation is dedicated to my parents, Mr. and Mrs. Rolland M. Reed, for all their support and patience in the pursuit of my higher education.
"Conservation is the wise use of natural resources."
Aldo Leopold (1942)
"The control of nature is won, not given."
Charles Hoyt (1958)
"I don't believe in paying for the
same real estate twice"
Gen. George S. Patton (1944)
"Air Cav, Air Mobile"
1st Cavalry Division USARVN (1965) ACKNOWLEDGMENTS
The author wishes to express his sincere gratitude to the following persons. Special thanks are extended to his advisor, Professor Franklin
R. Hall, for his support and guidance throughout the course of this research. Thanks are due Professors H. R. Krueger and H. R. Willson and
Mr. D. L. Reichard as members in his reading and examining committees.
Appreciation is extended to Professors D. L. Reichard, R. D. Fox and
R. D. Brazee and Mr. D. L. Collins for their expert advice and supplying invaluable experiment equipment; to D. A. McCartney and J. F. Mason for assistance in certain aspects of this research; to Mr. B. L. Bishop and
Dr. R. A. J. Taylor for their analysis of certain data; to D. M. Pavuk,
M. J. McLeod, R. N. Royalty and B. A. Lucius for their assistance in collection of certain data. Lastly, great thanks are extended to cooperators and sponsors; R. A. Badertscher, B. D. Livingston
(Schlessman Seed Co.), Dr. H. M. LeBaron (Ciba-Geigy), Dr. D. H. De
Vries (Dow Chemical), Dr. J. L. Clapp (Triazone), B. C. Peacock
(Yetter), D. A. Thompson (Cat Pumps) and R. M. Reed and R. M. Longman
(Caterpillar Tractor). VITA
August 11, 19 6 1 ...... Born - Portland, Oregon
1984...... B.S., Agriculture,
University of Wyoming,
Laramie, Wyoming
1984-86 ...... Graduate Research Assistant,
Department of Entomology,
University of Missouri,
Columbia, Missouri
1986...... M.S., Entomology, University
of Missouri, Columbia,
Missouri
1987-1989 Graduate Research Associate,
Department of Entomology,
The Laboratory for Pest
Control Application
Technology, Ohio
Agricultural Research and
Development Center/The Ohio
State University, Wooster,
Ohio
iv PUBLICATIONS
Reed, J. P., F. R. Hall, D. L. Reichard and H. R. Willson. 1990. Influence of nozzle upon the control of the stalk borer using chlorpyrifos and cyfluthrin. J. Environ. Sci. Health B24(l):23-38.
Reed, J. P., A. J. Keaster, R. J. Kremer and G. F. Krause. 1989. Synergistic and antagonistic responses of soil insecticide-herbicide combinations for corn rootworm, Diabrotica spp. control. J. Environ. Sci. Health B(4):325-334.
Reed, J. P., F. R. Hall, and D. Trimnell. 1989. Effect of encapsulation of thiocarbamate herbicides within a starch matrix for overcoming enhanced degradation in soils. DER STARKE 41:184-189.
Reed, J. P., R. J. Kremer, and A. J. Keaster. 1989. Activities and degradation of several insecticides and herbicides in soils poised for enhanced carbamate and thiocarbamate degradation. J. Environ. Sci. Health B24:(l) 23-36.
Reed, J. P., R. J. Kremer, A. J. Keaster, and H. D. Kerr. 1989. Microbial degradation of some soil insecticides, herbicides and insecticide-herbicide combinations. Bull. Environ. Contain. Toxicol. 42:676-681.
Reed, J. P. and D. A. McCartney. 1988. 1 4 ^ Edition insecticide and acaracide tests, 1988 Evaluation of Corn Rootworm Application Methods. p. 221.
Reed, J. P. and D. A. McCartney. 1988. 14^ Edition insecticide and acaracide tests, 1987 Evaluation of Corn Rootworm Application Methods. pp. 221-222.
Hall, R. R., B. A. Lucius, J. P. Reed, and R. N. Royalty. 1988. Tree fruit insects - 1988. Chemical Investigations, Entomology Series 88- 1 .
Hall, F. R . , J. P. Reed, D. L. Reichard, B. A. Omilinsky, and C. Maurer. 1988. Evaluation of no-touch pesticide use system. ASTM 9 ^ Symposium on Pesticide Formulations and Application Systems. 9:27-36.
Hall, F. R. and J. P. Reed. 1988. Improved biotargeting of soil-applied pesticides. Application to Seeds and Soil, BCPC monograph No. 39:351-361. Reed, J. P., R. J. Kremer, and A. J. Keaster. 1987. Characterization of microorganisms in soils exhibiting accelerated pesticide degradation. Bull. Environ. Contam. Toxicol. 39:776-782.
Hall, F. R . , J. H. Gregory, B. A. Lucius, M. A. Zajac, and J. P. Reed. 1987. Tree fruit insects - 1987. Chemical Investigations, Entomology Series 87-1.
Reed, J. P., A. J. Keaster, R. J. Kremer, and H. D. Kerr. 1985. Missouri corn pesticide performance survey. Univ. Missouri Agric. Exp. Stn. SR 714.
FIELDS OF STUDY
Major Field: Entomology
Application Technology
Professor: F. R. Hall
Vi TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS...... ii
DEDICATION...... iii
VITA ...... iv
LIST OF T A B L E S ...... ix
LIST OF FIGURES...... xiii
INTRODUCTION ...... 1
CHAPTER
I. INFLUENCE OF NOZZLE UPON THE CONTROL OF THE COMMON STALK BORER USING CHLORPYRIFOS AND CYFLUTHRIN...... 13
II. CONTACT AND VOLATILE TOXICITY OF SOIL INSECTICIDES TO BLACK CUTWORM LARVAE AND CARABID BEETLES ...... 28
Introduction...... 28 Materials and Methods ...... 31 Results and Discussion...... 37 Summary...... 41 References...... 43
III. COMPARISON OF CORN ROOTWORM SOIL INSECTICIDE APPLICATION METHODS...... 53
Introduction...... 53 Materials and Methods ...... 60 Results and Discussion...... 68 Summary...... 78 References...... 81
vii TABLE OF CONTENTS (CONTINUED)
CHAPTER
IV. ESTABLISHMENT OF AN ACTION THRESHOLD FOR LARVAL CORN ROOTWORM CONTROL AND A COST/BENEFIT ANALYSIS OF SOIL INSECTICIDE APPLICATION MACHINERY...... 98 Introduction...... 98 Materials and Methods ...... 106 Results and Discussion...... 110 Summary...... 118 References...... 121 V. INFLUENCE OF SOIL, PRECIPITATION AND APPLICATION METHODOLOGY UPON THE LATERAL AND HORIZONTAL MOVEMENT OF THREE SOIL INSECTICIDES...... 135 Introduction...... 135 Materials and M e t h o d s...... 138 Results and Discussion...... 143 Summary...... 151 References...... 151
BIBLIOGRAPHY...... 160
APPENDIX...... 172
viii LIST OF TABLES
TABLE PAGE
1. Field study - percent infestation of corn by stalkborers after chlorpyrifos application with various nozzles and application rates...... 19
2. Field study - percent infestation of corn by stalkborers after cyfluthrin application with various nozzles and application rates...... 19
3. Laboratory study - percent contact area, percent net mortality on soil and glass for second instar stalkborer larvae...... 21
4. Laboratory study - percent contact area, percent net mortality on soil and glass for third instar stalk borer larvae...... 23
5. Percent cumulative distribution of droplets produced by an XR8003 and a TK1.5 nozzles using an Aerometrics Phase Doppler Particle Analyzer ...... 25
6 . Toxicity of chlorpyrifos, DPX-43898 and terbufos 48 hours after infestation of fourth instar BCW larvae: 1987 .... 46
7. Toxicity chlorpyrifos, DPX-43898, fonofos, and terbufos 48 hours after infestation of fourth instar BCW larvae: 1988 and 1989 ...... 47
8 . Toxicity of chlorpyrifos, DPX-43898, fonofos and terbufos 48 hours after application to plots with endemic carabid beetles: 1987, 1988, and 1989 ...... 48
9. Summary of LD5Q and upper and lower confidence values for fourth instar A. ipsilon larvae, Abascidus permundus, and Pterostichus chalcites for chlorpyrifos, DPX-43898, fonofos, and terbufos...... 49
10. Means of percent area contacted by fourth instar BCW larvae and three species of adult carabid beetles...... 50
11. Components of final multiple regression equation for 48hour BCW larval mortality by soil insecticides (r^ = 0.3885) . . 51
12. Components of final multiple regression equation for 48 hour adult carabid beetle mortality (Number/12m row) by soil insecticides (r^ ■= 0.3678)...... 52 1987 Wooster and Bluffton, Ohio. Soil insecticide application method efficacy test...... 84
1988 Wooster, Ohio. Soil insecticide application method efficacy test...... 85
1988 Bluffton, Ohio. Soil insecticide application method efficacy test...... 86
1988 Western Branch. Soil insecticide application method efficacy test...... 87
1988 Milan, Ohio. Soil insecticide application method efficacy ...... 88
1989 Wooster, Ohio. Soil insecticide application method efficacy test...... 89
1989 Western Branch. Soil insecticide application method efficacy test...... 90
1989 Milan, Ohio. Soil insecticide application method efficacy ...... 91
Summary of three month evaluations for dissolvable pouch integrity ...... 92
Drawbar pounds pull (DBPP), drawbar horsepower pull (DBHP), fuel consumption, total chemical costs and total operating costs for six scenarios of rootworm insecticide application machinery operation ...... 93
Chi-square goodness of fit tests of the negative binomial distribution for corn rootworm larvae populations at Bluffton, Western Branch and Milan, Ohio sites in 1988. . . 125
Chi-square goodness of fit tests of the negative binomial distribution for corn rootworm larvae populations at Western Branch and Milan, Ohio sites in 1989...... 126
Required number of samples per hectare (acre) to attain a level of sampling accuracy for assessing rootworm larval populations at respective sites and years...... 127
X 26. Scouting costs ($) per hectare ($/acre) for a given level of accuracy at respective sites and years ...... 128
27. T-values and significance levels of regressions describing describing the relationship of first larval counts and root ratings to predict yield in the untreated checks for respective sites for 1988...... 129
28. T-values and significance levels of regressions describing describing the relationship of first larval counts and root ratings to predict yield in the untreated checks for respective sites for 1989...... 130
29. Cost/benefit ratios of various soil insecticide application treatments without fertilizer for Milan, Ohio site in 1988 and 1989...... 131
30. Cost/benefit ratios of various soil insecticide application treatments with fertilizer for Milan, Ohio site in 1988 and 1989...... 132
31. Cost/benefit ratios of various soil insecticide application treatments without fertilizer for Western Branch site in 1988 and 1989...... 133
32. Cost/benefit ratios of various soil insecticide application treatments with fertilizer for Western Branch site in 1988 and 1989...... 134
33. Lateral movement of soil insecticides at the Bluffton s i t e ...... 173
34. Movement of soil insecticides in conventional and no-till plots at the Wooster site in 1987 ...... 174
35. F-values and P>F of insecticide x sampling method of various application methods at four sites in 1988 ...... 175
36. F-values and P>F of insecticide x sampling method of various application methods at three sites in 1989...... 176
37. Soil sampling date for residue analysis of soil insecticide applied at four sites in 1988...... 177
38. Soil sampling date for residue analysis of soil insecticide applied at three sites in 1989 ...... 178
39. Agronomic and edaphic factors for the evaluation of various soil insecticide application methods ...... 179
XI 40. Water solubility, vapor pressure, mammalian toxicity and GUS values of chlorpyrifos, diazinon and isazophos ...... 180
41. Cumulative precipitation and air temperature for soil sampling periods at four sites in 1988 ...... 181
42. Cumulative precipitation and air temperature for soil sampling periods at four sites in 1989 ...... 182
xii LIST OF FIGURES
Figure Page
1. Slot injector developed at the Laboratory for Pest Control Application Technology, The Ohio Agricultural Research and Development Center Wooster, Ohio 44691...... 94
2. Skid injector of Clapp et al. (1985); Lower lefthand corner, close-up of a countersunk nozzle mounted to a skid p l a t e ...... 95
3. Point injector developed by Baker (1985) used to inject liquid fertilizer at last cultivation...... 96
4. Sites used to represent soil regions throughout Ohio . . . 97
5. Insecticide x sampling method at the Wooster site in 1988, 1.12 kg (AI)/ha (1 lb/a) planting time application in conventional tillage...... 156
6 . Insecticide x sampling method at the Wooster site in 1988, 1.12 kg (AI)/ha (1 lb/a) planting time application in n o - t i l l ...... 157
7. Insecticide x sampling method at the Wooster site in 1989, 1.12 kg (AI)/ha (1 lb/a) planting time application in conventional tillage...... 158
8 . Insecticide x sampling method at the Wooster site in 1989, 1.12 kg (AI)/ha (1 lb/a) planting time application in n o - t i l l ...... 159
9. Insecticide x sampling method at the Bluffton site in 1988, 1.12 kg (AI)/ha (1 lb/a) planting time application . 160
10. Insecticide x sampling method at the Milan site in 1988, 1.12 kg (AI)/ha (1 lb/a) planting time application . 161
xiii 11. Insecticide x sampling method at the Milan site in 1989, 1.12 kg (AI)/ha (1 lb/a) planting time application . 162
12. Insecticide x sampling method at the Wooster site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application in conventional tillage ...... 163
13. Insecticide x sampling method at the Wooster site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application in n o - t i l l...... 164
14. Insecticide x sampling method at the Wooster site in 1989, 1.12 kg (AI)/ha (1 lb/a) injection application in conventional tillage ...... 165
15. Insecticide x sampling method at the Wooster site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application in n o -till...... 166
16. Insecticide x sampling method at the Bluffton site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application in conventional tillage...... 167
17. Insecticide x sampling method at the Western Branch site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application. . . . 168
18. Insecticide x sampling method at the Western Branch site in 1989, 1.12 kg (AI)/ha (1 lb/a) injection application. . . . 169
19. Insecticide x sampling method at the Milan site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application. . . . 170
20. Insecticide x sampling method at the Milan site in 1989, 1.12 kg (AI)/ha (1 lb/a) injection application. . . . 171
21. Insecticide x sampling method at the Wooster site in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application in conventional tillage ...... 172
xiv 22. Insecticide x sampling method at the Wooster site in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application in no-till...... 173
23. Insecticide x sampling method at the Wooster site in 1989, 0.37 kg (AI)/ha (0.33 lb/a) injection application in conventional tillage ...... 174
24. Insecticide x sampling method at the Wooster site in 1989, 0.37 kg (AI)/ha (0.33 lb/a) injection application in no- tillage ...... 175
25. Insecticide x sampling method at the Bluffton site in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application in conventional tillage...... 176
26. Insecticide x sampling method at the Western Branch site in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application in conventional tillage...... 177
27. Insecticide x sampling method at the Western Branch site in 1989, 0.37 kg (AI)/ha (0.33 lb/a) injection application in conventional tillage...... 178
28. Insecticide x sampling method at the western Branch site in 1989 0.37 kg (AI)/ha (0.33 lb/a) injection application in conventional tillage...... 179
29. Insecticide x sampling method at the Milan site in 1989, 0.37 kg (AI)/ha (0.33 lb/a) injection application in conventional tillage...... 180
30. Soil sampling scheme for planting timetreatments ...... 181
31. Soil sampling scheme for slotinjection treatments...... 182
XV INTRODUCTION
Pesticides provide innumerable benefits through the control of various pests which destroy 33% of all food crops. The use of such pesticides has also lead to significant costs to both the environment and the public health. Indeed, this problem is magnified further as newer, more potent soil-applied pesticides are being developed and used while corresponding improvements in delivery systems have materialized at a much slower pace or not all (Hall and Reed, 1988).
Certainly, the regulatory processes have mandated that accountancy of pesticide be required in the review process of a pesticide (Hall and
Reed, 1988). Pimentel and Levitan (1986) estimated that less than 0.1% of pesticides applied ever reach the target pest. Hence, the remaining
99,9% cannot always be accounted for and is assumed to pose a grave threat to non-targets. The costs associated with loss of wildlife, human health risk and accelerated loss of other resources (i.e. beneficial insects and plants) are referred to as 'external costs'.
Estimation of external costs remains cryptic, yet has been used in the pesticide registration/re-registration process as well as other regulatory aspects of pesticides.
1 2
Presently, modification of pesticide formulations is viewed as the
most expedient way around some of these problems as well an opportunity
to improve bioavailability. In the future, targeting of pesticides to
the pest will be emphasized to a greater extent. However, in the past,
research programs such as Integrated Pest Management (IPM), the
Pesticide Impact Assessment Program (PIAP), both of which have granting
responsibilities for improving the use of pesticides in agriculture and
reducing the negative impact of pesticides on the environment, have
fallen short of their goals. The engineer, entomologist, plant
pathologist and weed scientist are the core of such an extensive program
whose purpose is to improve pesticide application. In order to attain
such goals, multidisciplinary research is required. Tlnfortunately, this
was not the case, for example in the five year period of 1983-88
agricultural engineers received about 25% as much in PIAP funding as
agronomists and entomologists combined (Waldron personal communication).
It is difficult to imagine that greater emphasis was not placed upon
application technology [i.e. Agricultural Engineering] despite the
warnings of pending legislative opposition to pesticides emanating from
environmental groups.
Corn (Zea mays) is one of several cash crops that is extensively planted in the United States. Estimates of areas planted were
approximately 26 million hectares (65 million acres) in 1989 (USDA-ERS, 1989). Not only have we witnessed the dramatic increase in corn acreage treated with herbicides (from 11% up to 90%) and insecticides (1% up to
40%) from 1952 to 1976; we have also seen a doubling of acreage and
tripling of corn yields (Durest and Black, 1977). More recently,
Suguiyama and Carlson (1985) found 58% of the corn acreage in 1984-85 was treated with a soil insecticide to control the corn rootworm pest complex (Northern corn rootworm, Diabrotica barberi Smith and Lawrence;
Southern corn rootworm, Diabrotica undecimpunctata howardi Barber; and
the Western corn rootworm Diabrotica virgifera virgifera LeConte).
Acreage treated for corn rootworms was not only greater than any other corn insect pest but also greater than any other crop pest in the U.S..
Approximately $1 billion is spent annually in the United States to control corn rootworms (Metcalf 1986).
Unfortunately, the majority of corn rootworm insecticide application research was limited to only granular formulations (Apple et al. 1969,
Mayo and Peters 1978, and Tollefson et al. 1987). Two noteworthy studies by Musick (1974), Mayo (1976), indicated the less persistent soil insecticides performed better as liquid post-planting treatments.
However, the general consensus was granular formulations were safer and easier to use at planting and cultivation. Farmers preferred the simplicity of planting time applications while implement dealers did not view the demand for retrofitting cultivators with granule metering units as profitable. Hence, one does not see a 'glut' of cultivators on the market with granule applicators (Indeed, it is difficult to find this piece of machinery at any used implement dealer!). So the incentive to develop and practice a truly integrated pest management program for corn rested on the justification of prophylactic applications of granular soil insecticides at planting (Foster et al. 1986).
The concept of pesticide targeting is defined as the ability to maximize pesticide efficiency through better, more accurate placement.
Manipulations which may lead to optimization of pesticide placement deal primarily with timing and coverage associated with improved placement by pesticide application. Thus, pesticide efficiency may be increased by reduced amounts of active ingredient that, if properly distributed and timed may reduce the amount of active ingredient yet manitain or even increase pesticide efficacy.
Consideration of earlier application technology research of corn soil insecticides was 'aimed' almost exclusively at corn rootworms.
Unfortunately, the concepts of targeting a soil insecticide to control corn rootworms does not apply to other corn soil insect pests. For example, rootworms are subterranean and feed primarily upon the roots of graminaceous plants, specifically when feeding is on corn roots the rootworm is classified as a pest. Damage to the corn plant is primarily the result of physiological stress, which can be compounded by environmental conditions. However, other corn soil insect pests such as the stalkborer (Papianema nebris Guenee') and black cutworm (Agrotis 5 ipsilon Hufnagel) are not subterranean in nature and reduce corn crop yields by stand reduction. Therefore, the concepts of targeting a soil insecticide to control cutworms and stalkborers are not the same as corn rootworm targeting parameters. Further, cutworms and stalkborers have not commanded the level of research attention as rootworms. Therefore, further investigations into understanding and improving the pesticide targeting processes for individual soil insect pests of corn were undertaken.
The first study was initiated in 1988 to assess the role of nozzle type in controlling stalkborers in the field. Although a majority of soil insecticides used to control corn rootworms are formulated as granules, these are not as effective as liquid formulations to control stalkborers for several reasons. First, the stalkborer is a new pest because it is prevalent in row crop (corn) conservation tillage systems, which is one of many recent management innovations to reduce soil erosion. Second, such tillage practices do not favor rootworms ecologically, so there is less need for a rootworm insecticide. Third, conservation tillage practices alter the soil properties to such a great extent that granular soil insecticides may not perform as well as in conventional tillage conditions. Finally, the stalkborer is a very mobile pest which spends most of its time in its host (corn seedling), moving on the soil surface only to search for a new, healthy corn plant.
Detection of this pest and the subsequent application of a liquid 6 formulation of the soil insecticide requires certain degree of timing and application accuracy. Hence, one can see that a liquid formulation of a soil insecticide, which is highly toxic to the stalkborer and can be uniformly applied, is required. However, since the stalkborer is mobile for a short period of its immature life, this suggests the acquisition of dose must be optimized by uniform spray coverage on soil through proper selection of nozzles.
Next, laboratory studies were initiated to define what parameters of the spray delivery process are required to optimize control of stalkborers. Both droplet sizing through high resolution measuring devices and percent area coverage via image analysis were utilized to accomplish this objective. Bioassays involving the use of specifically sized droplets and dosages elaborated further upon whether stalkborer control was a largely a function of dose [concentration] or coverage by a particular insecticide. This information reflected how important selection of insecticide and subsequently nozzle may be used to optimize stalkborer control.
The second study was an assessment of the importance of certain granular soil insecticides physico-chemico, environmental relationships on both the black cutworm efficacy and predatory carabids in 1987 through 1989. Further, the principles of improved targeting of soil insecticides to control stalkborers apply to cutworms because they feed on corn plants but do not infest and are more vulnerable to a soil insecticide. Also cutworms seek shelter by burrowing into the soil.
Thus, cutworms are not only more vulnerable to a liquid soil
insecticides but they may not be as vulnerable to predatory carabid beetles. The implications of this scenario rely primarily upon the ability of the relatively non-persistent liquid insecticide to control cutworms regardless of non-target effects, such as predatory carabids.
Unfortunately, the deleterious effects of environment upon a soil insecticide, let alone a liquid formulation that is not persistent, may further reduce cutworm control. In addition, if predatory carabid populations are reduced, then neither insecticidal nor natural control measures will reduce stand loss that may be attributed to cutworm feeding.
Granular soil insecticides demonstrate increased value by controlling not only rootworms but cutworms as well. One aspect of pesticide targeting that is largely ignored is timing. As indicated above, liquid formulations tend to be less persistent than granular formulations. In the absence of scouting, granular formulations are applied as preventative treatments against cutworms and rootworms because of the delayed release of active ingredient is in concert with the appearance of these pests. Further, this release may be slow enough to extend the "window of vulnerability" while maintaining a dose which is not detrimental to beneficial predators such as the carabid beetles.
Therefore, targeting principles are drastically different between a granular formulation and a liquid formulation. The crux of these targeting principles lies in the formulations ability to modify certain physical parameters of the active ingredient.
Such information will be invaluable in not only explaining why a particular soil insecticide on the market controls only black cutworms but it also stresses the importance of retaining healthy predatory carabid populations by exploiting certain physio-chemical relationships through pesticide targeting concepts. Hence, this information may be used to help select future insecticide candidates.
The last study dealt with the development of a new application technology (slot injection) to deliver corn rootworm soil insecticides under various soil conditions throughout most of Ohio. Although this study was initiated in 1987, the incentive to continue this study in
1988-1989 stemmed from the potential ban of carbofuran granules which are highly toxic to birds. In addition, granular soil insecticides which were once thought to be safe to the user are now considered acute and chronic health hazards. Hence, pesticide targeting principles were largely ignored. Needless to say, improvement of the application of rootworm soil insecticides must also include environmental and health considerations.
The use of granular soil insecticides has relied upon the active ingredients ability to be leached vertically throughout the soil profile into the locality of the rootworms. Prior studies also ignored some basic principles of pesticide targeting and were concerned only with observing active ingredient movement from the granule to the target pest. Implications of granule placement upon non-target organisms and
assumption of optimal timing were the two most ignored factors of
targeting.
Since slot injection addressed placement of a liquid soil
insecticide beneath the soil surface and near the microenvironment of
the rootworm, the remaining problem to be addressed was timing. Rescue
treatments of corn rootworm entail incorporation of soil insecticide granules at last cultivation, known also as lay-by application. Unlike
the planting time applications of granular soil insecticides, rescue treatments may be used on a treat when neceassary basis. The worst case scenario of rescue treatment to control rootworms was a test of the adaptability of slot injection machinery. Therefore, studies for establishment of an economic threshold for larval corn rootworm scouting for Ohio was initiated.
To demonstrate the importance of the concept of soil insecticide targeting, a comparison of not only efficacy with different soil insecticides but the total operating costs of applying soil insecticides was performed. This information was the foundation of a cost benefit/analysis of pesticide application machinery. The cost/benefit analysis which not only included internal costs but external costs for the two different application methodologies was addressed. Annual comparisons of these analyses determined whether or not the application 10 of the soil insecticide was profitable under respective growing conditions.
It was further assumed that a soil insecticide behaved in a toxicant-like manner. However subsequent studies on the movement of soil insecticides and susceptibility of rootworms to various soil insecticides yielded contrary findings. To address these and other environmental concerns, movement of insecticides that were applied with different application methodologies in various edaphic and environmental conditions were investigated in 1987 through 1989. Not only could the environmental concerns be addressed, but a comparison of years could explain why a soil insecticide that was applied in a specific manner provided a specific level of efficacy. 11
REFERENCES
Apple, J. W . , E. T. Walgenbach, and J. W. Knee. 1969. Northern corn rootworm control by granular insecticide application at planting and cultivation. Journal of Economic Entomology 62:1033-1035.
Durest, D. D. and E. T. Black. 1977. Changes in Farm Production and Efficiency, USDA-ERS SR-581.
Foster, R. E., J. J. Tollefson, J. P. Nyrop, and G. L. Hein. 1986. Value of adult corn rootworm population estimates in pest management decision making. Journal of Economic Entomology 79:303-310.
Hall, F. R. and J. P. Reed. 1988. Improved biotargeting of soil applied pesticides. Application to seeds and soil. BCPC Monograph No. 39:351-361.
Mayo, Z. B. 1976. Control of the western and northern corn rootworm with liquid starter fertilizer - insecticide combinations and the influence of depth of placement. Journal of Economic Entomology 70:234-236.
Mayo, Z. B. and L. L. Peters. 1978. Planting vs. cultivation time applications of granular soil insecticides to control larvae of corn rootworms in Nebraska. Journal of Economic Entomology 71:801-803.
Metcalf, R. L. 1986. forward, pp. vii-xi. J. L. Krysan & T. A. Miller [eds.], Methods for the study of pest Diabrotica. Springer-Verlag, New York.
Musick, G. J. 1974. Efficacy of liquid starter fertilizer combinations for control of resistant northern corn rootworm larvae. Journal of Economic Entomology 67:668-670.
Pimentel, D. and L. Levitan. 1986. Pesticides: amounts applied and amounts reaching pests. BioScience 36:86-91.
Suguiyama, L. F. and G. A. Carlson. 1985. Field crop pests: farmers report the severity and intensity. USDA-ERS, AI-487 I
12
Tollefson, J. J. , G. L. Hein, and J. D. Oleson. 1987. Influence of application technique on insecticidal control of corn rootworm in three tillage systems. Down to Earth 43:16-18.
USDA-ERS. 1989. Agricultural Outlook. USDA-ERS AO-156.
Waldron, A. 1989. Personal Communication. CHAPTER I
INFLUENCE OF NOZZLE TYPE UPON THE CONTROL OF THE STALKBORER USING CHLORPYRIFOS AND CYFLUTHRIN
KEY WORDS: chlorpyrifos, cyfluthrin, PDPA, image analysis
J. P. Reed1 , F. R. Hall and H. R. Willson
Laboratory for Pest Control Application Technology Ohio Agricultural Research and Development Center The Ohio State University Wooster, OH 4469
ABSTRACT
Field experiments were conducted in corn plots during 1988 that were artificially infested with stalkborers, Papianema nebris (Guenee'). Two atomizers, a flatfan and a flood nozzle chosen for different droplet size distributions were used to apply two insecticides, chlorpyrifos and cyfluthrin at two application rates. Nozzles, insecticides, rates, and associated interactions were evaluated for control of stalkborer in the field. Laboratory studies involved application of insecticides to soil and glass via a spray track for bioassay at field application rates.
Image analysis of percent area traveled on water sensitive paper by stalkborers was compared to droplet percent area covered to obtain
Contribution from the Laboratory for Pest Control Application Technology, Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691.
13 percent area contacted per insect. Droplet size distributions for each nozzle were obtained using an Aerometrics particle sizing instrument.
Significant differences in stalkborer control were attributed to percent
area covered by smaller droplets measured by image analysis.
INTRODUCTION
The stalkborer, (Papianema nebris) has become an important insect pest where corn is grown in a conservation tillage system (Musick, 1970).
The adult moths oviposit on fall plantings of rye, wheat and grass weeds. Upon hatching during the following spring, stalkborer (SB) larvae will tunnel into and occupy any tender plant of appropriate size.
Weed control programs have apparently led to the prevalence of this pest
in conservation tillage systems because preplant herbicides kill weed hosts occupied by larvae. Thus, larvae move from dead weeds to emerging corn (Stinner et al. 1984). The control strategy for this pest relies heavily upon insecticide application prior to movement of stalkborer larvae from dead weeds to corn. Since movement is random, timing an insecticidal spray directly to larvae is impractical. However, larval movement on soil or crop debris containing an insecticide residue from a prior application has resulted in varied levels of control (Davis and
Pedigo, 1989). Thus, the question of proper insecticide application with knowledge of timing applications should lead to better and more efficient stalkborer control. The objective of this research was to determine the respective roles of nozzle parameters, insecticide and rates used to control stalkborers. 15 METHODS AND MATERIALS
Field Studies
Field experiments were conducted at the Ohio Agricultural Research and Development Center, Wooster, OH, during 1988. Field plots were 2 rows wide and planted to corn at 51,000 seeds/ha, measuring 12 m long by
1.52 m wide with a 76 cm row spacing. A factorial design consisting of the following factors: 2 insecticides, 2 application rates and 2 nozzles was replicated three times. Chlorpyrifos (4% emulsifiable concentrate) was applied at 1.12 and 2.24 kg a.i./ha and cyfluthrin (25% emulsifiable concentrate) was applied at 0.011 and 0.006 kg a.i./ha to each treatment replicate. A back pack sprayer equipped with either an XR8003 flat fan or TK-1.5 flood nozzles applied insecticides at a rate 250 1/ha; travel speed of applicator was 4.0 km/hr and nozzle pressure was 210 kPa.
During insecticide application in the field, water sensitive spray cards (2.5 x 7.5 cm) were placed at ground level 6 cm from the row for assaying percent area covered by each nozzle and insecticide.
After insecticides were applied tc plots, a 500 ml bottomless plastic cup was installed to retain 1, third instar larvae per plant. Larvae were placed on the treated soil inside of each cup. There were 20 larvae per treatment replicate and percent infestation of plants was recorded 72 hours later. Prior to analysis of variance, all data were transformed using an arcsine transformation. Duncan's Multiple Range
Test was used at the 0.05 significance level for mean separation. 16
Laboratory Studies
Laboratory studies consisted of bioassays using second and third instar SB larvae on soil and glass surfaces with the same application parameters as in the field studies. However, a spray track (single nozzle) was utilized to apply insecticides (Same criterion as the field study) to soil and glass. A lOOg aliquot of soil (Wooster silt loam) was placed in a 500 ml plastic cup which was sprayed and subsequently infested with SB larvae. A glass petri dish was used as a two-dimensional surface which was also sprayed and later infested with both second and third instar SB larvae in respective runs. Second and third instar SB larvae were used for the assay because of their availability and both instars are considered economically important.
Mortality counts on both soil and glass were recorded at 6 hours post-treatment. A factorial design replicated three times was employed; means for percent net mortality (Abbott, 1925) were transformed
(arc-sine) prior to analysis of variance. Duncan's Multiple Range Test was the preferred mean separation method at p = 0.05 level.
During insecticide application in the laboratory, water sensitive spray cards (2.5 x 7.5 cm) were placed at the same level 6 cm from the row of petri dishes containing larvae for assaying percent area covered from each nozzle. Also, second and third instar larvae (n = 20) were allowed to track for approximately 30 seconds on at least two water sensitive cards after dorsal application of a droplet of water, which also acted as a stimulus for movement. Image analysis using a Dapple
Systems, Inc., image analyzer was used to obtain percent area covered 17 for field and laboratory deposition study cards and SB tracked cards.
Percent area covered data was obtained because the resolution of the
image analyzer was 50 um, therefore any information pertaining to droplet counts or sizing would be biased towards the larger end of the droplet spectrum. Further, drop sizing and the coalescence of droplets on water sensitive spray cards may be distorted by the pesticide formulation and concentration of the spray solution, requiring a spread factor (Bouse et al. 1989). Hence, the use of percent area covered data on water sensitive paper was chosen for this study. Both percent area
covered images of the SB and the nozzle were stored via computer for later retrieval to calculate percent area contacted by an individual
insect. Next, the area contacted by SB was superimposed on the sprayed
cards from laboratory studies to obtain a percent area contacted per
larvae of a given instar. Separation of means by Duncan's Multiple
Range Test at the p = 0.05 level was performed on the percent covered
data.
Since the resolution of the image analyzer was only 50 um, spray
drop sizing analysis by this instrument was not utilized. An
Aerometrics phase doppler particle analyzer (PDPA) was used to determine
the droplet diameters delivered by the flatfan and flood nozzles. The
PDPA operates over a 35-fold range in drop diameter and data was acquired in the center of the spray pattern 45 cm below the nozzle orifice in each of four replicated runs. Preliminary studies at the
LPCAT have demonstrated that variations in spray characteristics between different measurements of the same nozzle using the same operating parameters require >1,500 droplets in the sample to approach statistical
significance at the 0.05 level. However, the present study included
over 2,000 droplets and the individual nozzle operation time was never
less than 30 seconds which was the minimum time required for >90% validation. Calibration of the PDPA is accomplished by measuring water
droplets in the center of a XR 8001 flat fan nozzle pattern. Setup calibration varied by + 8 um (4.7%) during the study. The Dv Dv 5, and Dy g was determined for percent spray volumes of 10, 50 and 90%.
For example, the Dv 5 , indicates that 50% of the spray volume is contained in drops with diameters less than the Dv>5 value which is known as the volume median diameter [VMD].
RESULTS AND DISCUSSION
Field Studies
In Table 1, infestation levels for chlorpyrifos applications were
significantly lower than the untreated check. No significant
differences were observed between the flatfan nozzle delivering 1.12 and
2.24 kg a.i./ha, as well as the flood nozzle applying 1.12 kg a.i./ha.
However, the flatfan nozzle applying chlorpyrifos at 2.24 kg a.i./ha had
significantly lower SB infestation levels than the flood nozzle at the
same rate.
Cyfluthrin applications by flatfan and flood nozzles and the
resultant infestations of SB are presented in Table 2. No significant
differences were observed between the flood nozzles applying 0.011 and
0.006 kg a.i./ha and the untreated check. 19
TABLE 1
Field Study - Percent Infestation of Corn by Stalk Borers^ After Chlorpyrifos Application with Various Nozzles and Application Rates.
Nozzle Rate (kg a.i./ha) % Infestation after 72 hr
Flatfan XR8003 2.24 6.6 a
Flatfan XR8003 1.12 26.6 ab
Flood TK1.5 2.24 33.3 b
Flood TK1.5 1.12 26.6 ab
Untreated Check 86.6 c
TABLE 2
Field Study - Percent Infestation of Corn by Stalkborers After Cyfluthrin Application with Various Nozzles and Application Rates.
Nozzle Rate (kg a.i./ha) % Infestation after 72 hr
Flatfan XR8003 0.011 13.3 a
Flatfan XR8003 0.006 20.0 a
Flood TK1.5 0.011 66.6 b
Flood TK1.5 0.006 86.6 b
Untreated 93.3 b
^Means following the same letter are not significantly different at p =
0.05 level of significance using Duncan's Multiple Range Test. The contrast between chlorpyrifos and cyfluthrin applications
apparently lies not only with the interaction between active ingredient, mode of action and timing, but also how the application was made.
Perhaps this is why such variable SB control is obtained by
Farmers/applicators. Since percent contact area (contacted by the SB) is a function of both percent area covered by the spray nozzle and the total area exposed by the crawling insect, quantification of the parameters are essential. Thus, the hypothesis we are trying to address, aside from the nozzles, concerns the percent area covered by the insect and the insecticide as well as the efficacy of an insecticide to control SB.
Laboratory Studies
The percent contact area in Tables 3 and 4 is defined as the product of the average area covered by the SB larvae (second and third instars) and the portion of coverage of the droplets produced by a given nozzle. This assessment is dependent upon the actual width of the insect tarsi or in the case of larviform insects those areas likely to contact the substrate traveled upon; droplet size and density produced by a given atomizer. Note in Table 3 that percent contact area of second instar SB larvae by flatfan (47.7, 59.7 chlorpyrifos; 39.3, 41.7 cyfluthrin) was nearly double the contact area of the flood nozzle
(26.5, 26.0 chlorpyrifos; 17.7, 19.7 cyfluthrin) for both insecticides
(Table 3). The significance of percent contact area is borne out in the percent net mortality data. Two separate substrates (glass represented a two dimensional surface whereas soil was three-dimensional) bioassays indicated differences between not only laboratory and field data but the actual surface area itself (glass, vs. soil). Again, the flatfan nozzle resulted in a 2X greater mortality than the flood nozzle. However, differences between mortalities on soil and glass were apparent. This may be accounted for by : 1) three dimensional nature of soil; 2) the adsorptive capacity of soil and 3) the movement
TABLE 3
Laboratory Study - Percent Contact Area, Percent Net Mortality on Soil and Glass3 for Second Instar Stalk Borer Larvae.
% Net Mortality
Insecticide Rate(kg a.i ./ha) Nozzle % Contact Soil Glass
Chlorpyrifos 2.24 Flatfan 47.7 b 63.3 abc 88.3 a
1.12 Flatfan 59.7 a 61.6 ab 80.0 a
2.24 Flood 26.5 c 30.0 c 31.6 c
1.12 Flood 26.0 c 43.3 cde 50.0 b
Cyfluthrin 0.011 Flatfan 39.3 b 75.0 a 85.0 a
0.005 Flatfan 41.7 b 60.0 abc 80.0 a
0.011 Flood 17.7 c 53.3 bed 60.0 b
0.005 Flood 19.7 c 41.6 de 61.6 b
3Means following the same letter are not significantly different at the p “ 0.05 level of significance using Duncan's Multiple Range Test. patterns of stalkborers on different substrates (soil and glass) is different. Each of these could have a negative impact upon insecticide availability/dose transfer. If each pesticide droplet/deposit is observed on a given substrate in the field such as different kinds of plant debris, an appreciate for percent area covered rather than number of droplets per unit area is apparent. Nonetheless, data on third
instar larvae (Table 4) showed similar trends concerning percent contact area and percent net mortality on soil and glass as in Table 3.
However, the difference lies in percent contact area of each instar and droplet size and density produced by each nozzle. Regardless of rates,
the flatfan nozzle applying chlorpyrifos to second instar larvae averaged 53% contact area in Table 3, while in Table 4 a 62% average
area of contact was observed for chlorpyrifos application to third
instar SB larvae. No differences were observed between the average percent contact area of second and third instar SB larvae after cyfluthrin was applied by a flatfan nozzle (Tables 3 & 4). When chlorpyrifos and cyfluthrin were applied by a flood nozzle, negligible differences (approximately 1%) were observed between the percent contact area of both second and third instar SB larvae.
Since a definition of the inert composition of the formulations was not readily available for chlorpyrifos and cyfluthrin and rates of active ingredient applied were drastically different, this data shows the complexity of differences between the active and inert ingredients of the formulation, atomization properties of each nozzle and the contact area that may be required for acceptable field performance. 23 TABLE 4
Laboratory Study - Percent Contact Area, Percent Net Mortality on Soil and Glass^ for Third Instar Stalk Borer Larvae.
% Net Mortality
Insecticide Rate(kg a.i./ha) Nozzle % Contact Area Soil Glass
Chlorpyrifos 2.24 Flatfan 63.2 a 86.6 a 85.0 a
1.12 Flatfan 62.0 a 63.3 ab 86.6 a
2.24 Flood 24.3 cd 36.6 be 53.3 ab
1.12 Flood 25.7 cd 28.3 c 31.6 b
Cyfluthrin 0.011 Flatfan 44.5 b 83.3 a 88.3 a
0.006 Flatfan 36.0 be 66.6 ab 86.6 a
0.011 Flood 18.5 d 38.3 be 51.6 ab
0.006 Flood 20.7 d 41.6 be 40.0 b
^Means following the same letter are not significantly different at the
p = 0.05 level of significance using Duncan's Multiple Range Test.
Similar field studies have demonstrated that small droplets with uniform coverage resulted in greater efficacy against a wide range of pests (Palmer et al. 1983; Abdalla and Scopes, 1983; Uk and Courshee,
1982). On the glass surface, both vertical and horizontal droplet
spread would create a 'topographical' effect as the droplet dried.
Therefore, on glass the SB larvae would have to travel between droplets
if they are able to detect and avoid droplets, while on soil traveling
'crests' or islands of uncontaminated soil might insure SB survival.
This phenomenon has also been studied on leaf surfaces for other pesticides and respective substrates (Johnstone, 1973; Ford and Salt,
1983) and has been the impetus for behavioral resistance research in
cockroaches (Rust and Reierson, 1978).
Pragmatically, the initial screening of an insecticide may take place on glass or some flat surface. Topical application of an
insecticide to an insect or a flat surface which will be in subsequent
contact with the insect usually entails applying a large sized droplet
(Shepard, 1959). For example, it is not uncommon to apply a 4 ul
droplet which has a 1980 um diameter (nearly 2 mm in diameter). This is not realistic from an application machinery standpoint in which 500 um
sized droplets are considered large (Matthews, 1983). However, in the
development process of an efficacious and economical insecticide, the
compatibility of insecticide formulation and application machinery must be addressed. To demonstrate the difference in droplet size
distribution produced by flatfan and flood nozzles, Table 5 presents the
drop diameters (Dv 5 and g) for 10, 50 and 90 percent cumulative volume distributions. A diameter for a given percent cumulative volume
distribution is defined as the droplet diameter for which the given
percentage of a spray volume is in that and smaller diameter droplets.
A standard measure of droplet size is the volume median diameter Dv 5 .
Note in Table 5 that there was no significant difference between
flatfan and flood nozzles at Dv ■]_. However, the median value diameters were significantly different; the flatfan had a larger median 25 TABLE 5
Percent cumulative distribution^ of droplets produced by an XR8003 and a TK1.5 nozzles using an Aerometrics Phase Doppler Particle Analyzer.
Nozzles Pressure (kPa) Dv.l °V.5 ®v. 9
Flatfan XR8003 210 118 a 250 b 342 a
Flood TK1.5 210 123 a 216 a 395 b
%eans following the same letter are not significantly different at the p =* 0.05 level of significance using Duncan's Multiple Range Test.
volume diameter droplet, while the Dv g demonstrated a larger sized diameter for the flood nozzle. In addition, the portion of specifically sized droplets whether produced by two different types of atomizers
(i.e. comparison thereof) may not be the same, thus the percent contact area between two atomizers is more likely to be different than the comparison of equivalent nozzles. This may partially explain the large differences between flood and flatfan nozzles in both the laboratory and field data. Although field studies relied upon percent infestation as a control parameter for SB and laboratory studies entailed the use of SB mortality counts, other studies have shown repellency and reduced ovipositon may be elicited by different size droplets of insecticides and acaricides (Adams et al. 1988; Aim et al. 1987; and Munthali, 1984). 26 CONCLUSIONS
This research demonstrated how discrepancies between nozzles used
to apply liquid soil insecticides for controlling SB infestations may
arise. Moreover, the variable of application methodology, such as nozzle selection, droplet atomization properties, and percent area
contacted by the target, demonstrated how little is known about the dynamics of dose transfer in pesticide application efficiency. Further detailed studies on the basic droplet size, density (#/cm2) and dose per droplet may lead to a better understanding of dose transfer to SB larvae.
ACKNOWLEDGMENTS
The authors extend a sincere thank you to Research Associate, D. A
McCartney for technical assistance throughout the project.
REFERENCES
Abdalla, M. R. and N. E. A. Scopes. ICPP Research Report 3A-R15. (1983).
F. R. Hall, I. A. Rolph and I. H. H. Adams. BCPC 3C-1:169-174. (1988)
Aim, S. R., D. L. Reichard, and F. R. Hall. Journ. Econ. Entomol. 80:517-520. (1987).
Bouse, L. F., Kirk, I. W. and Bode, L. E. ASAE/CSAE Meeting, Quebec, Canada Paper 891006. (1989).
Davis, P. M. and L. P. Pedigo. Environ. Entomol. 18:In Press. (1989).
Duncan, D. B. Biometrics. 11:1-41. (1955)
Ford, M. G. and D. W. Salt. Crit. Rev. Appl. Chem. 23:26-81. (1983)
Johnstone, D. R. Pesticide Formulations (ed. Valkenburg, W. van) New York, N.Y. Marcel Dekker., pp. 625. (1973). Matthews, G. A. Pesticide Application Methods. New York, N.Y. Longman Group Ltd., pp. 325. (1983).
Musick, G. J. Proc. N.E. No-Till Conference 1:44-59. (1970).
Munthali, D. C. Crop Protection 3:327-334. (1984).
Palmer, A., I. A. Wyatt and N. E. A. Scopes. ICPP Research Report 3A-R16. (1983).
Rust, M. K. and D. A. Reierson. Journ. Econ. Entomol. 71:704-708. (1978).
Shepard, H. H. Methods of Testing Chemicals on Insects. Minneapolis, MN. Burgess Publ., pp. 355. (1955).
Stinner, B. R., D. A. McCartney, and W. L. Rubink. J. Ga. Entomol. Soc. (1984).
Uk, S. and R. J. Courshee Pestic. Sci. 13:529-536. (1982). CHAPTER II
CONTACT AND VOLATILE TOXICITY OF SOIL
INSECTICIDES TO BLACK CUTWORM LARVAE
AND CARABID BEETLES
Introduction
The Black Cutworm, Agrotis ipsilon (Hufnagel) causes serious, eco nomic damage to seedling corn when fourth through seventh instar larvae
chew through the stem coleoptile up to six leaf stage corn plants near
the soil surface (Clement and McCartney 1982, Story et al. 1983). Inte
grated pest management of A. ipsilon has relied upon scouting and the use of soil insecticide treatments (Story and Keaster 1982). Similar
studies have lead to the implementation of ecologically or physiologi
cally selective insecticides (Hull and Beers 1985, Mullin and Croft
1985) in integrated pest management programs. The frequency and sever
ity of a pest species has allowed the artificial selection of resistant predator populations to be the cornerstone of such programs (Croft 1982,
Hoy 1987). The .ability to lower insecticide use in one study by 50% so only the cotton leaf hopper, Pseudomoscelis seriatus (Reutter) was con trolled while beneficial insect populations were allowed to increase, yet maintain control of bollworm, Heliothis zea (Boddie) and budworm,
Heliothis virescens (F.), resulted in an $85.50/ha (34.20/a) net return
(Casey et al. 1975). A similar pest management strategy for A. ipsilon
28 could be adopted by selecting a predator friendly soil insecticide and may already be implemented if certain soil insecticides are used to con
trol A. ipsilon larvae.
Under some circumstances, insecticide treatment for control of A.
ipsilon larvae may not be necessary because a high endemic predator population keeps the pest population in check (Brust et al. 1986).
Carabid beetle adults and larvae comprise a large portion of A. ipsilon predators (Coaker and Williams 1963, Frank 1971, Brust et al. 1986).
The importance of these natural agents in controlling A. ipsilon larvae was first investigated by Best and Beegle (1977), Lund and Turpin (1977)
and later confirmed in the field by Brust et al. (1985).
Although carabids are considered as non-specific in their feeding habits, the importance of crop diversification (e.g. manipulation of
tillage and crop rotation practices) to such a predator may both in
crease its effectiveness in reducing pest populations (Sheehan, 1986)
and indirectly, affect pesticide use requirements. Brust et al. (1985)
demonstrated A. ipsilon larval feeding damage significantly increased where tillage and the soil insecticide, phorate had been used and this was attributed to phorate produced reductions in carabid populations.
The high toxicity of phorate to carabids had been documented previously
in laboratory studies (Critchley 1972, Tomlin 1975, Gholson et al.
1978). Great disparity exists between the comparative efficacies of soil insecticides for controlling A. ipsilon larvae (Harris 1968) and much of this may be due to differences in volatility and solubility of the in secticide active ingredient (Harris 1972). However, little is known about the physical properties of soil insecticide that may be exploited in the dose transfer process to protect endemic carabid populations while maintaining satisfactory A. ipsilon larval control.
The approach of insecticide dose transfer was pursued because the sporadic frequency and severity of the A. ipsilon/carabid complex
(Foster and Tollefson 1986) indicates a low probability of insecticide resistance despite the prophylactic use of granular soil insecticides
(Osteen and Kuchler 1986) this, and findings of other workers (Brust et al. 1985, Critchley 1972, Gholson et al. 1978, and Tomlin 1975) war ranted further work with this pest/predator complex. In this study, the effect of vapor pressure, water solubility, tillage, precipitation, and air and soil temperatures upon the toxicity of soil insecticides to A. ipsilon larvae and carabid beetles is investigated. The implications of these findings may aid the selection of an efficacious soil insecticide that is not harmful to an endemic carabid beetle population and yet will control A. ipsilon larvae. Moreover, defining the physical factors that appear to influence the differential toxicity of soil insecticides to A. ipsilon larvae and carabidae may be used as criteria for the selection and development of future soil insecticide candidates. 31
MATERIALS AND METHODS
Field Studies
The study was conducted at the Ohio Agricultural Research and Devel opment Center, in 1987 through 1989 on a Wooster silt loam soil (Typic
Fragiudalf) of high fertility. In 1987, the experimental design was a split-split-split plot design replicated three times (Cochran and Cox
1957). Main plots were insecticides; sub plots were method of applica tion (banding or in-furrow); sub-sub plots were tillage, (conventional and no-tillage); while sub-sub-sub plots were placement of fourth instar
A. ipsilon larvae in screened bottom and bottomless cups.
In 1988 and 1989, the experimental design was a split-split plot ' replicated three times (Cochran and Cox 1957). As in 1987, insecticides were the main plots. However insecticide placement was not a signifi cant factor and all treatments were banded ahead of the press wheel and tillage became the sub plot. The sub-sub plots were placement of larvae.
The soil insecticides tested throughout this study were the or- ganophosphates: chlorpyrifos (0,0 diethyl 0-3,5,6-trichloro-2-pyridinyl phosphorothioate), DPX-43898 (0,0-diethyl 0-1,2,2,2-tetrachloroethyl phosphorothioate) and terbufos (0,0-diethyl S-fcerfc-butylthiomethyl phophorodithioate). In 1988 and 1989, fonofos (0-ethyl S-phenylethyl phosphonodithioate) was included in the study. All soil insecticides were formulated as 15% granules and were applied at the rate of 1.12 kg 32 (AI)/ha (llb/a) by two electrically operated Gandy bokes mounted on a
two-row Allis Chalmers no-till planter. Granules were banded ahead of
the press wheel in an 18 cm (7 in) band in all three years of the study.
In 1987, granules were also applied as in-furrow treatment. Plots, con
sisting of two rows with 0.76 m (30 in) row spacing were planted to
'Illini Chief' sweet corn at a rate of 51,000 seeds/ha (20,000/a) on 15
May 1987, 12 May 1988 and 16 May 1989. Immediately after planting,
eight screened bottom and bottomless 500 ml (1 pint) plastic cups were
firmly set into each tillage plot over the rows where seed was planted
and soil insecticide granules were applied. One fourth instar A. ipsi
lon larvae was placed in each cup. No food was supplied to the A. ipsi
lon larvae during the study.
Mortality readings 48 hours post infestation were determined by prodding the larvae with a probe-like instrument. Mortality of A. ipsi
lon larvae in the screened cups (ca. 0.6 cm [0.25 in] above soil sur
face) indicated transfer of the soil insecticide to the insect was due
to volatility of the soil insecticide. A. ipsilon larvae that were placed in the bottomless cups burrowed into soil, dose transfer was most
likely due to contact action.
All A. ipsilon mortality data were adjusted for natural mortality by Abbotts formula (Abbott, 1925). Data were transformed (arc sine) prior to analysis of variance. Duncan's multiple range test (1955) was
used for mean separation (P = 0.05) using general linear models proce
dure (PROC GLM, SAS Institute 1982b, 139-199). 33 Counts of free ranging, endemic, moribund carabid adults in the
18 cm row band were recorded 48 hours post-application. These counts were restricted to the 18 cm band, to insure that the mortality was probably caused by that treatment. Since variation in the untreated check exceeded 20%, carabid counts were not adjusted for natural mortal ity. Data were subjected to analysis of variance procedures and sig nificance of means was determined by Duncan's multiple range test (1955) at (P = 0.05).
Laboratory Studies
Topical applications of all insecticides (chlorpyrifos, DPX-43898, fonofos, and terbufos) in this study were made to establish sensitivity and toxicity levels for fourth instar A ipsilon larvae, field caught carabid adults of the two species; Abascidus permundus L. and Pterosti- chus chalcites Say.
A digital microbalance was used to weigh a representative number of test insects to establish an average weight for each test group. The average weights were recorded to the nearest milligram. All solutions were made by dissolving technical grade material in acetone. Initial dosage rates were ten-fold serial dilutions (i.e. 100, 10, 1 , 0.1 ppm), when a range was established three other dosage values were tested that fit between the two ten-fold range values. There were 50 individuals per insecticide dosage, a total of 250 individuals was used for in creased precision (Robertson et al. 1984). Applications were made with 34 35 an ISCO Model M microapplicator equipped with a 0.25 ul glass luer tip tuberculin syringe. The materials were applied to the ventral portion of fourth instar A ipsilon larvae and carabid adults. Mortality counts were recorded at 24 h post application. All mortality counts were ad justed for natural mortality according to Abbott (1925). Probit analy sis to determine insecticide LD50 values and 95% confidence intervals for the respective species was accomplished by the computer program of
Trevors (1986). The non-overlap of 95% confidence intervals was used to determine whether LD^q values were significantly different among insec ticides for the given species.
Image analysis has been used to assess the contact-transfer of toxicity by acaricides to the twospotted spider mite, Tetranychus urti- cae Koch. (Hall et al. 1987). In our study, twenty, fourth instar A. ipsilon larvae were allowed to travel over water sensitive spray cards
(2.5 c m x 7.5 cm [3 x 5 in]) for one minute. Each insect was wetted by water dorsally prior to traveling on the water sensitive paper. The distance of travel in one minute was recorded. The image analysis sys tem consisted of an image analyzer (Dapple Systems Inc., Sunnydale,
Calif.), an Apple lie computer, a videcon video camera, RCA viewing monitor, printer and Image + software. The image of the A. ipsilon traveling on water sensitive paper was quantified and stored, on hard disk. Quantification information is based upon the percent area trav eled in one minute. The same procedure was performed for field caught adult carabids, Abascidus permundus L. and Pterostichus chalcites Say. 36 The percent area traveled data was arc sine transformed and differences described using the analysis of variance. Significance of means was tested by Duncan's multiple range test (1955) at the P = 0.05,
Multiple Linear Regression Study
The toxicity, vapor pressure, and water solubility of the respec
tive soil insecticides were noted (Worthing and Walker 1987); tillage and infestation placement of A. ipsilon larvae, annual precipitation were analyzed by the statistical procedures CORR and GLM (SAS Institute
1982b) to derive the simplest multiple linear regression for A. ipsilon
and carabid mortality caused by soil insecticides in this study. LD50 values of the two carabid species in the laboratory study were used in
the regression analysis. Ambient air and soil temperature means were
calculated based upon values 10 days prior to infestation and during the
48 h experimental period. As soil moisture would influence leaching of
a soil insecticide, ambient air and soil temperatures were also included
as variables in the multiple linear regression analysis (Harris 1968).
Precipitation is another important variable in the activation of granu
lar soil insecticides. These variables were used to describe the envi ronmental effects of the dose transfer process of soil insecticides to
A. ipsilon larvae and carabids in each year of the study. The topical
LD5Q values for each species was used to describe the greatest potential toxic effect for each insecticide. 37 RESULTS AND DISCUSSION
In 1987, significant differences in A. ipsilon mortality were ob
served among insecticide (F = 6.53, P < 0.0035, df = 2) and the insecti
cide X tillage X placement interaction (F = 6.62, P < 0.0033, df = 2) .
Application method was not a significant factor in 1987 (F = 0.96, P >
0.6659, df = 1), therefore all soil insecticides were banded in subse quent years. In 1988 and 1989, significant differences were observed
among insecticides (1988: F = 5.02, P < 0.003, df - 4; 1989: F ■=* 10.57,
P < 0.0001, df = 4),tillage (F = 8.69, P < 0.0054, df = 1), placement (F
= 31.02, P < 0.0001, df = 1), insecticide X placement (F = 13.58, P <
0.0001, df = 4) and tillage X placement (F = 8.71, P < 0.0054, df = 1)
interactions. Adult carabid mortality was significantly different among
soil insecticides during all years of the study (1987: F *=> 11.90, P <
0.0001, df = 3; 1988: F = 9.16, P < 0.0001, df = 4; 1989: F = 18.69, P <
0.0001, df = 4).
No significant differences were observed among chlorpyrifos appli
cations in no-till and placement of A. ipsilon larvae on ground, DPX-
43898 conventional tillage with placement on screen or DPX-43898 no-till
on ground. Chlorpyrifos and DPX-43898 were more toxic to A. ipsilon
larvae placed on ground in no-tillage plots than terbufos in either con ventional tillage with larvae placed upon screen or no-tillage with placement on ground (Table 6). Chlorpyrifos and DPX-43898 were more toxic to A. ipsilon larvae than fonofos and terbufos in 1988 and 1989 (Table 7). Carabid mortality was significantly greater in DPX-43898, fonofos and terbufos treated plots than chlorpyrifos and the untreated check plots in the three year duration of the study (Table 8).
Laboratory Studies
Topical LD5Q values and confidence intervals for the four insecti cides on fourth instar A. ipsilon larvae, Abascidus permundus L. and
Pterostiches chalcites Say are given in Table 9. Lethal dosage values for A. ipsilon larvae indicated DPX-43898 (2.96 ppm) had significantly greater toxicity than all other insecticides. Chlorpyrifos was the next most toxic insecticide (18.02 ppm), which was significantly different than all other insecticides. Both fonofos and terbufos displayed the highest LD50 values, respectively 309.01 and 367.72 ppm. The relative toxicity of the insecticides varied more among Pterostichus chalcites than the either A. ipsilon and Abascidus permundus. The order of toxic ity from greatest to lowest for Pterostichus chalcites is: chlorpyrifos>
DPX-43898> fonofos> terbufos; all insecticides were significantly dif ferent than each other. No significant differences were observed among the chlorpyrifos, DPX-43898 and terbufos LD^q values for Abascidus per mundus while fonofos appeared to be less toxic than the other insecticides.
Mean separation of contact areas associated with fourth instar A. ipsilon larvae and two species of adult carabid beetles demonstrated that A ipsilon larvae were significantly different than the two species 39 of adult carabids; and had at least three to ten times greater area ex posed on a smooth surface than any of the two species of adult carabids
(Table 10).
Multiple Linear Regression Study
The vapor pressures of chlorpyrifos, DPX-43898, fonofos and ter bufos are 2.5, 1.1, 28 and 35 mPa respectively (Worthing and Walker
1987) and comparing these values with A. ipsilon mortality (Tables 6 and
7) suggests that vapor pressure is a key factor in the dose transfer process of granular soil insecticides. Indeed, vapor pressure was one of three variables with a significant effect upon A. ipsilon mortality
(F = 21.11, P < 0.0001, df = 4, 127). Precipitation (F = 19.8 , P <
0.0002 , df = 4, 127) and location (F = , P < 0.0115 , df - 4, 127 ) were the other two significant factors of the multiple linear regression model (Table 6). Vapor pressure was also an important factor in the dose transfer process of carabid toxicity. Other important factors were precipitation, soil temperature, and intrinsic toxicity (F = 17.01, P <
0.0001, df = 4, 127) as indicated in Table 11.
The intrinsic toxicity of the insecticide was shown as a signifi cant factor in the dose transfer process to carabid beetles (F = 21.02,
P < 0.0001). Precipitation (F = 19.56, P < 0.0007), vapor pressure (F =
12.32, P < 0.0117) and soil temperature (F = 20.88, P < 0.0001) were additional factors responsible for carabid mortality in the field. 40 The significance of insecticide X placement and tillage X place ment interactions in 1989 demonstrated the importance of volatility in the acquisition of soil insecticides to both A. ipsilon larvae and cara bid beetles. In addition, the significance of tillage agrees with Brust et al. (1985) and suggests that 12 day precipitation (10 days prior + 2 days during the study), water solubility, air and soil temperature be included in development of the regression. Precipitation was signifi cant in partially explaining the dose transfer process to both A. ipsi lon larvae and carabid adults (Tables 11 and 12). Not only is moisture required for the activation of granular soil insecticides but this proc ess is driven by the amount of precipitation prior to and following the application of the soil insecticide (Burkhardt and Fairchild, 1967).
Since the activation and/or deactivation of a granular soil insecticide is dependent upon precipitation, the dose transfer of some soil insecti cides may be due to volatilization after the granular soil insecticide has been activated (Lichtenstein and Shulz, 1964). However, these fac tors do not explain why DPX-43898 caused such high mortality to both A. ipsilon larvae and endemic carabid populations (Tables 6, 7 and 8).
Therefore, intrinsic toxicity and soil temperature were used as vari ables to explain the behavior of soil insecticides against carabid popu lation (Table 12). Since DPX-43898 and terbufos carabid mortalities were not different in two of three years of the study and vapor pressure alone was not sufficient to explain the difference between these insec ticides to A. ipsilon larvae we concluded acquisition of DPX-43898 over came the dose transfer process by intrinsic toxicity. Soil temperature 41 was important because this suggested the cool/wet spring of 1989 hin
dered DPX-43898 acquisition and resulted in lower carabid mortality.
SUMMARY
Our studies have demonstrated that granular soil insecticides with
differing vapor pressures resulted in varying levels of A. ipsilon lar vae control and carabid beetle mortality. In most cases, the two soil
insecticides with high vapor pressures, fonofos and terbufos, resulted
in limited mortality of A. ipsilon larvae, and significant carabid mor
tality was observed. DPX-43898 was also toxic to carabids and high in
trinsic toxicity was shown to overcome the lack of acquisition due to
low vapor pressure. The two soil insecticides, chlorpyrifos and DPX-
43898, possessed lower vapor pressures resulting in greater A. ipsilon
larval mortality and lower carabid beetle mortality. Therefore, it is
inferred that A. ipsilon larvae acquire a lethal dose of a soil insecti
cide with lower vapor pressure occurs primarily by contact. Alterna
tively, the limited contact afforded by carabid beetle adults and subse
quent mortality suggested volatilization was the route of dose transfer
for fonofos and terbufos.
ACKNOWLEDGMENT
We thank David McCartney for many helpful suggestions and assistance in
this study and Reed Royalty for manuscript preparation. A special
thanks is extended to Armon Keaster and Mary Jackson for providing A.
ipsilon larvae used in this study. Thanks are due Beth Lucius, Murtick 42 McLeod, Daniel Pavuk and Mark Zajac for helping infest A. ipsilon lar vae. Robert Treece, Roger Williams, Ben Stinner and Andrew Adams pro vided helpful suggestions on early drafts of this manuscript. A con tribution of the Laboratory for Pest Control Application Technology, The
Ohio Agricultural Research and Development Center, and the Ohio State
University, Journal Article Series No. 208-89. 43 REFERENCES
Abbott, W. S. 1925. A method for computing the effectiveness of an insecticide. J. Econ. Entomol. 18: 265-267.
Best, R. L., and C. C. Beegle, 1977. Food preferences of five species of carabids commonly found in Iowa cornfields. Environ. Entomol. 6 : 9-12.
Brust, G. E., B. R. Stinner and D. A. McCartney. 1985. Tillage and soil insecticide effects on predator-black cutworm (Lepidoptera: Noctuidae) interactions in corn agroecosystems. J. Econ. Entomol. 78: 1389-1392.
Brust, G. E., B. R. Stinner and D. A. McCartney. 1986. Predation by soil inhabiting arthropods in intercropped and monoculture agroecosystems. Agric. Ecosys. Environ. 18: 145-154.
Burkhardt, C. C. and M. L. Fairchild. 1967. Bioassay of field treated soils to determine bioactivity and movement of insecticides. J . Econ. Entomol. 60: 1602-1610.
Casey, J. E., R. D. Lacewell and W. Sterling. 1975. An example of economically feasible opportunities for reducing pesticide use in commercial agriculture. J. Environ. Qual, 4: 60-64.
Clement, S. L. and D. A. McCartney. 1982. Black cutworm (Lepidoptera: Noctuidae): measurement of larval feeding parameters on field corn in the greenhouse. J. Econ. Entomol. 75: 1005-1008.
Coaker, T. H. and D. H. Williams. 1963. The importance of some carabidiae and staphylinidae as predators of the cabbage root fly, Erosia brassicae (Bouche '). Ent. Exp. Appl. 6 : 156-64.
Cochran, W. G., and G. M. Cox. 1957. Experimental designs, 2nd ed. John Wiley and sons, Inc. New York.
Croft, B. A. 1982. Arthropod resistance to insecticides: a key to pest control failures and successes in North American apple orchards. Entomol. Exp. Appl. 31: 88-110.
Critchley, B. R. 1972. A laboratory study of the effects of some soil applied organophosphorus pesticides on Carabidae (Coleoptera). Bull. Entomol. Res. 62: 229-42.
Duncan, D. B. 1955. Multiple range and multiple F tests. Biometrics 11: 1-41. 44 Foster, R. E. and J. J. Tollefson. 1986. Frequency and severity of attack of several pest insects of corn in Iowa. J. Kan. Entom. Soc. 59:269-274.
Frank, J. H. 1971. Carabidae (Coleoptera) as predators of the red-backed cutworm (Lepidoptera: Noctuidae) in central Alberta. Can. Entomol. 103: 1039-1044.
Gholson, L. E., C. C. Beegle, R. L. Best and J. C. Owens. 1978. Effects of several commonly used insecticides on cornfield carabids in Iowa. J. Econ. Entomol. 71: 416-418.
Hall, F. R., D. L. Reichard and S. R. Aim. 1987. A system for the examination of the pesticide dose transfer process. Pesticide formulations and the pesticide dose transfer process. ASTM 7: 85-92.
Harris, C. R. 1969. Laboratory evaluation of candidate materials as potential soil insecticides. III. J. Econ. Entomol. 63:782-87.
Harris, C. R. 1972. Factors influencing the effectiveness of insecti cides. Ann. Rev. Entomol. 17: 177-198.
Harris, C. R. and H. J. Svec. 1968. Toxicological studies on cutworms. III. Laboratory investigations on the toxicity of insecticides to the black cutworm, with special reference to the influence of soil type, soil moisture method of application, and formulation on insecticide activation. J. Econ. Entomol. 61: 965-969.
Hoy, M. A. 1987. Developing insecticide resistance in insect and mite predators and opportunities for gene transfer, pp. 125-138. In H. M. LeBaron, R. 0. Mumma, R. C. Honeycutt and J. H. Duesing [eds], Biotechnology in agricultural chemistry. American Chemical Society Symposium Series No. 334.
Hull, L. A. and E. H. Beers. 1985. Ecological selectivity: modifying chemical control practices to preserve natural enemies, pp. 103-121. In M. A. Hoy and D. C, Herzog [eds], Biological control in agricultural IPM systems. Academic, Orlando, Fla.
Lichtenstein, E. P. and K. R. Shulz. 1964. The effects of moisture and microorganisms on the persistence and metabolism of some organophosphate insecticides in soils with special emphasis on parathion. J. Econ. Entomol. 57: 618-627.
Lund, R. D. and F. T. Turpin. 1977. Serological investigation of black cutworm consumption by ground beetles. Ann. Entomol. Soc, Amer. 70:322-324.
Mullin, C. A. and B. A. Croft. 1985. An update on the development of selective and biodegradable pesticides, pp. 123-150. In M. A. Hoy 45 and D. C. Herzog [eds], Biological control in agricultural IPM systems. Academic, Orlando, Fla.
Osteen, C. and F. Kuchler. 1986. Potential bans of corn and soybean pesticides: economic implications for farmers and consumers. USDA-ERS., Agric. Econ. Report 546.
Robertson, J. L., K. C. Smith, N. E. Savin and R. J. Lavigne. 1984. Effects of Dose Selection and Sample Size on the Precision of Lethal Dose Estimates in Dose-Mortality Regression. J. Econ. Entomol. 77: 833-837.
SAS Institute. 1982a SAS user's guide: basics SAS Institute, Cary NC. 1982b SAS user's guide: statistics. SAS Institute, Cary NC.
Sheehan, W. 1986. Response by specialist and generalist natural enemies to agroecosystem diversification: a selective review. Environ. Entomol. 15:456-461.
Story, R. N. and A. J. Keaster. 1982. Development and evaluation of a larval sampling technique for the black cutworm. J. Econ. Entomol. 12:241-244.
Story, R. N . , A. J. Keaster, W. B. Showers, J. T. Shaw and V. Wright 1983. Economic-threshold dynamics of black and claybacked cutworms (Lepidoptera: Noctuidae) in field crops. 13: 131-137.
Tomlin, A. D. 1975. The toxicity of insecticides by contact and soil treatment to two species of ground beetles. Can. Ent. 107:529-532.
Trevors, J. T. 1986. A BASIC Program for Estimating LD5Q Values Using the IBM-PC. Bull. Environ. Contam. Toxicol. 37: 18-26.
Worthing, C. R. and S. B. Walker. 1987. The pesticide manual: a world compendium, 8^ edition. BCPC. Table 6. Toxicity of chlorpyrifos, DPX-43898 and terbufos 48 hours after infestation of fourth instar BCW larvae: 1987
Insecticide Tillage Placement^ % Net Mortality chlorpyrifos conventional screened 22.88 abed chlorpyrifos conventional ground 28.46 abc chlorpyrifos no-till screened 14.99 bede chlorpyrifos no-till ground 33.35 ab DPX-43898 conventional screened 37.91 a DPX-43898 conventional ground 25.39 abed DPX-43898 no-till screened 10.84 cde DPX-43898 no-till ground 31.56 abc terbufos conventional screened 4.24 de terbufos conventional ground 18.84 abede terbufos no-till screened 19.99 abede terbufos no-tillage ground 1.02 e
■^Means in a column followed by the same letter are not significantly different (P = 0.05; Duncan's multiple range test). ^Placement by screen and ground are indicative of dose acquisition by volatilization and contact, respectively. 47 Table 7. Toxicity of chlorpyrifos, DPX-43898, fonofos and terbufos 48 hours after infestation of fourth instar BCW larvae: 1988 and 19891 .
% Net Mortality
Insecticide 1988 1989 chlorpyrifos 35.42 a 11.46 a DPX-43898 38.54 a 10.42 a fonofos 13.54 b 4.20 b terbufos 6.25 b 3.12 b
•*-Means in a column followed by the same letter are not significantly different (P = 0.05; Duncan's multiple range test). 48 Table 8 . Toxicity of chlorpyrifos, DPX-43898, fonofos and terbufos 48 hours after application to plots with endemic adult carabid beetles: 1987, 1988, and 1989^.
Dead Carabids/12 m row
Insecticide 1987 1988 1989 chlorpyrifos 0.08 b 0.91 b 0.16 b DPX-43898 1.33 a 4.16 a 0.58 b fonofos — 4.66 a 3.50 a terbufos 1.66 a 3.16 a 3.42 a untreated 0.25 b 0.75 b 0.16 b
•1-Means in a column followed by the same letter are not significantly different (P = 0.05; Duncan's multiple range test). Table 9. Summary of LD50 and upper and lower confidence values for fourth instar A. ipsilon larvae, Abascidus permundus and Pterostiches chalcites for chlorpyrifos, DPX-43898, fonofos, and terbufos.
Species
A.. ipsilon Abascidus permundus Pterostiches chalcites ld50 Upper Lower LD50 Upper Lower ID5Q Upper Lower Insecticide chlorpyrifos 18.02 22.56 13.37 3.01 6.28 1.54 1.44 0.84 2.52
DPX-43898 2.96 4.77 1.62 2.08 2.64 1.53 3.94 4.61 3.36 fonofs 309.01 448.96 168.65 42.58 86.76 20.13 5.68 11.16 2.74 terbufos 367.72 579.56 183.43 4.67 6.58 3.38 37.08 46.55 28.32
Means in a column followed by the same letter are not significantly different (P = 0.05; Duncan's multiple range test).
-p> 1 0 Table 10. Means of percent area contacted by fourth instar BCW larvae and three species of adult carabid beetles^-.
Species % Area Contacted/min
BCW fourth instar 70.13 a Abascidus permundus 20.71 b Pterostichus chalcites 9.35 b Scarites substriatus 10.49 b
■^Means in a column followed by the same letter are not significantly different (P > 0.05; Duncan's [1955] multiple range test). 51
Table 11. Components of final multiple regression equation for 48 hour BCW larval mortality by soil insecticides (r^ => 0.3885).
Variable Coefficent P > T
Precipitation - 12.3248 0.0000 Vapor Pressure - 0.5334 0.0000 Location 0.7500 0.0115 Table 12. Components of final multiple regression equation for 48 hour adult carabid beetle mortality (number/12m row) by soil insecticides (r^ = 0.3678).
Variable Coefficent P > T
LD50 -0.3119 0.0000 Precipitation 0.5505 0.0007 Vapor Pressure 0.4006 0.0117 Soil Temperature 0.2130 0.0000 CHAPTER III
COMPARISON OF CORN ROOTWORM SOIL
INSECTICIDE APPLICATION METHODS
Introduction
The importance of soil insecticide use is borne out in expenditures
for their use. Metcalf (1986) calculated $1 billion is spent for granu lar soil insecticides to control the corn rootworm complex (Northern corn rootworm, Diabrotica barberi Smith and Lawrence; Southern corn rootworm, Diabrotica undecimpunctata howardi Barber; Western corn root worm, Diabrotica virgifera virgifera LeConte). Unfortunately, many drawbacks to the use of granular soil insecticides have just begun to be noticed. In particular, the granular soil insecticides have been scru tinized and re-registration of granular soil insecticides may be in jeopardy due to bird toxicity. Balcomb (1983) reported that carbofuran was toxic to red-shouldered hawks. In a current review of carbofuran for re-registration is pending further bird toxicity data. Two other soil insecticides, phorate and terbufos will be up for similiar review
53 54 in late 1989 (Urbain, 1989). Present concern for contamination of
groundwater and surface water run-off has placed granular soil insecti
cides in a precarious position if point source pollution regulations were rigidly enforced (Baker, 1985). Another concern is user exposure.
Granular compounds were once thought to be the safest pesticide formula
tions, but recent studies indicate user exposure to granular soil insec
ticides may pose a greater threat to applicator health than previously
thought (McDonald, 1987). Current application technology for prophylac tic use of granular soil insecticide use does not alleviate these prob
lems but may actually aggravate them (Graham-Bryce, 1988).
The current alternatives for integrated corn pest management, spe cifically rootworms, are dependent upon crop rotation and in the case of
continuous corn, prophylactic use of granular soil insecticides (Foster
et al. 1986). Earlier studies concerning the application of soil insec
ticides have typically dealt only with planting and cultivation treat ment comparisons (Apple et al. 1969, Mayo & Peters, 1978, Tollefson et
al. 1987). Further, research of alternative application strategies of corn rootworm insecticides, although multidisciplinary in nature, has not been funded (Ellis, 1982).
The study of Rider and Dickey (1982) vividly illustrated the problem issues of calibration and the lack of reliable methodology, frequency and accuracy. Their data showed that 25% of the granular applicators under-applied by approximately 21% and 1 in 3 over-applied by approxi mately 40%. In addition, 4 of 10 boxes on the same equipment had more than 50% variations in error. Studies by IGI (personal communication,
Bates 1984) with granular pesticide formulations metered with Noble V- belt units showed variations in repeated runs ranging from 18-104% with the same formulation. Variation between products was even higher, dem onstrating that each formulation has its own characteristics of flow, degradation and bridging. Ellis (1982), in a study of grower-applied granular pesticides, showed that 13% of the equipment applied less than
80% of the recommended rate and 50% of the equipment varied the delivery rates by more than 20%. Ellis also confirmed that increasing travel speeds confounded patterns of granule delivery.
Erbach and Tollefson (1983) observed irregular distribution of fluo rescent coated blank insecticide granules in soil and they concluded that some form of active incorporation would be helpful. They also al luded to the possible disturbing effect of wind on granule distribution.
Bergman et al. (1986) demonstrated that the density of granular products played a significant role in the performance of the compounds, i.e., the more dense granules had less drift potential. When wind shields con sisting of vinyl floor molding were put into place, little if any drift occurred. This relatively simple and inexpensive modification could be accomplished easily by farmers. However, in the absence of meaningful incentives, i.e., well documented economic benefits, and/or regulatory statutes, this simple but effective modification is not likely to occur on the average farm. An example of refined targeting of soil-applied pesticides for sur
face and subterranean pests was the blowing of granular pesticides into
15 cm deep (6 in) vertical bands in freshly prepared seed beds prior to
lateral distribution (Whitehead, 1983).
Slot injection is another type of placement for soil insecticides in
which a nozzle is placed directly behind the coulter, the penetration
depth of which can varied, and the pesticide is "shot" into the slot
(Figure 1). The advantage of this system over others currently in use
is the direct placement of the compound at the target site, the mechani
cal simplicity, the flexibility of delivery depth, liquid formulation
uniformity and potentially low application rate (Hall and Reed, 1988).
The beginnings of this technology, injection of herbicides into
slots, was conceived as an alternative to placing herbicides in layers beneath the soil surface (Solie et al. 1983). Slot injection of the mobile, thiocarbamate herbicides was first researched by Jasa et al.
(1986). Further, incentive for development of this machinery has empha
sized alternative methods for applying herbicides in reduced tillage.
The use of pre-plant incorporated herbicides, a majority of which con
trol grasses could be limited under reduced tillage scenarios and grass weed control might be jeopardized. Other attempts have been made at
directly injecting by a skid mounted high pressure nozzle (Figure 2) not
only pesticides but fertilizers as well (Clapp et al. 1985). The use of
point injection, a wheel with hollow spokes through which the hub is machined for letting chemical mixtures pass when the spoke in the ground has met with limited success (Figure 3). Nozzle clogging, rocks and hub
leakage has resulted in limited grower acceptance. However, as a fer
tilizer applicator, not only were yields increased over conventional,
earlier applicatons of nitrogen but injection at the last cultivation,
lay by period were reduced by 30-50% (Baker, 1985).
The relationship of nitrogen in root regeneration of rootworm dam
aged plants is still unclear. Lilly and Gunderson (1952) reported ap plication rates of N aided the reduction of damage by rootworms through
increased root regeneration. More recent studies (Foster et al. 1986)
demonstrated increased N applications were positively correlated with higher root ratings; while Spike and Tollefson (1988) concluded "root damage ratings increased with moderate N application but decreased with high N levels." Not only does the concept of injecting pesticides into
the soil question the present status and scope of integrated pest man agement but other 'external forces' such as fertility and weed manage ment could be advanced further if application technology was seriously considered. Hence a truly cost effective integrated pest management program may be realized in corn.
There are increasing problems (real and perceived) associated with the handling of pesticides in agriculture. All known data reveal that the greatest levels of exposure encountered with the use of a pesticide occurs at the mixer-loader stage. 58 The user first encounters the chemical in its package which is de signed to avoid hazards in shipping and storage. The rules governing container safety during shipping have grown increasingly complex al
though efforts at harmonizing some of the conflicting requirements have been successful. Among the safety innovations in packaging are water- soluble film packages, mini-bulk containers and bag-box-packaging. Al though the products in soluble bags are nearly always contained, they usually avoid waste and overuse in weighing, and minimize container dis posal, however they require the entire bag be utilized. Consequently, precision dose targeting and IPM concepts may be constrained under some combinations of tank size/spray volume conditions. Market forces demand different sizes which results in higher inventory requirements. How ever, the advantages outweigh the disadvantages. The concept is an ex tremely useful one and because of reduced exposure and the disposal ad vantages, should provide improvements for agriculture (Miller, 1987;
Reed et al. 1988). Further, other means to reduce pesticide exposure have relied upon direct in line injection from the container to the pes ticide application machine (Reichard and Ladd, 1983).
Peters (1975) first tried to estimate the value of annual soil in secticide applications in Iowa but found the analysis to be biased as to underestimate the importance of soil insecticide application. Turpin and Theime (1978) evaluated the economic impact of soil insecticides in
Indiana for the period of 1972-1975 and concluded "that the prophylactic use of soil insecticides is seldom profitable in Indiana." Insecticides 59 applied at planting time to control corn rootworm, (Diabrotica spp.) for example, may fail to provide adequate control due to dissipation (i.e. degradation, leaching) before the soil insecticide is needed for corn rootworm control (Kuhlman, 1984). Many of the problems could be elimi nated by the development of an efficient and practical pesticide injec tor (Hall and Reed, 1988; Suett, 1988; Thompson, 1988). Not only could such a piece of machinery be used to apply an insecticide and/or fertil izer but the tool bar could serve as a platform from which another spray bar could be used to apply a post-emergence herbicide. Potentially, all three operations could occur regardless of reduced tillage constraints
(Hall and Reed, 1988; Reed et al. 1988). Hence, the opportunity to truly compare the economic impact of a slot injection machine as an al ternative to the conventional granular banding machinery at planting may finally be realized.
This study was conducted to fulfill three objectives. The first objective deals with the comparison between insecticide efficacy trials comprised of planting time treatments, cultivation and slot injection in various tillages at locations throughout Ohio. The second objective was to address some current problems with pesticide containers, namely health risk to user via exposure and container disposal. The last ob jective was to compare slot injection to granular banders in planters via equipment investment analysis (Reed et al, 1987). /
60 Materials and Methods
Field Studies 1987-89
Four sites were selected for this study throughout Ohio, three of which were located in Western Ohio with soil types representative of the
Midwest (Figure 4). By convention, we will refer to these individual sites as follows: Bluffton, located near Bluffton, Hancock County,
Ohio; Western Branch, plot location at this outlying field station near
South Charleston, Clark County, Ohio; and Milan, located near Milan,
Huron County, Ohio. The fourth site, Wooster, had plots located at the
Ohio Agricultural Research and Development Center near Wooster, Wayne
County, Ohio, in soils which are indicative of Western Appalachia or
Eastern Cornbelt (Figure 4). Each site was under study for a minimum of two years and the respective agronomic and edaphic information is given
in Table 39. Row spacing at all sites was 76 cm. (30 in.)
A randomized complete block design was replicated four times in 1987 and 1988 at all sites except Western Branch which had three replicates.
In 1989, only three replicates were used at the Western Branch and Woos ter site, the Milan site was replicated four times.
Note the Wooster site had sweet corn var, Illini Chief grown in the trials while Western Branch did not have planting and cultivation treat ments; the Milan site did not have cultivation treatments. The only comparisons between applications of soil insecticides with and without liquid fertilizers were at Western Branch and Milan sites. Soil insec ticides were applied at the rate of 1.12 kg (AI)/ha (1 lb/a) for both planting time and cultivation treatments while injection treatments were applied at 1.12 kg (AI)/ha (1 lb/a) and 0.37 kg (AI)/ha (0.33 lb/a).
Brace was applied at 0.74 kg (AI)/ha (0.66 lb/a) instead of 1.12 kg
(AI)/ha (1 lb/a). Injection application was made at a delivery rate of
187 L/ha (20 gpa). All fertilizers were applied at a rate of approxi mately 52.6 kg/ha (47 lb/a) of actual N using 28% formulations of URAN fertilizers.
Where there were three and four replicates at a given site, six and five roots were respectively dug and washed. All roots were rated ac corded to the Iowa 1-6 root rating scale (Hills and Peters, 1971). The numerical categories of this root rating system are as follows: 1) No damage; 2) Feeding scars apparent, but roots not eaten off by larvae to within 3.75 cm (1.5 in) of the plant; 3) Several roots eaten off to within 3.75 cm (1.5 in) of the plant but node not completely destroyed;
4) One node destroyed; 5) Two nodes destroyed; and 6) Three or more nodes destroyed.
The rating of 3 is of particular interest since it approximates the economic injury level to corn by rootworm damage (Foster et al. 1986).
Yields were based upon the amount of grain harvested per lOOO*-*1 of an a
(5.25 m [17.5 ft] strips; mean of two strips per plot) according to
Willson et al. (1987). 62 Soil insecticide application machinery use was based upon the spe
cific soil insecticide formulation in use. All granular formulations
required the use of granular metering units. Planting time treatments
at the Wooster and Bluffton sites were applied by Gandy metering units
(Gandy Company, Box 528, Owatonna, MN, 55060-0528) placing granules
ahead of the press wheel in 18 cm (7 in) bands. Similarly, Gandy meter
ing units applied soil insecticide granules for cultivation With spread
ers spaced 60 cm (24 in) ahead of cultivator shoes on both sides of the
row at Wooster and Bluffton sites.
All planting time soil insecticide applications at the Milan site were made with a John Deere (John Deere, 1400 Third Ave., Moline, IL
61265) Max-Emerge 7000 planter and planting dates are listed in Table
39 for all sites.
Rootworm pressure at each site was not uniform, hence comparisons between sites for a given treatment were not made. However, one site
which was known for consistent rootworm pressure was the Western Branch
site. Had a third year of data been obtained at the Bluffton site, this
site might have demonstrated the most significantly consistent level of
rootworm pressure of any site in Ohio. Although the Milan site was in
continuous corn for 12 years rootworm pressure was variable. . This site
was unique due to its sandy soil type. In 1988, rootworm pressure was
not severe, but in 1989 rootworm pressure was more severe than any site.
At the Wooster site rootworm pressure appeared to decline. This might have been due to the continuous early planting of sweet corn. Since 63 sweet corn tends to tassel and silk earlier than field corn, these con
ditions do not favor heavy oviposition by adult rootworm females.
Therefore, the continuous planting of sweet corn had an attrition-like
effect upon annual rootworm populations and damage.
Liquid formulations of soil insecticides used in this study were
applied by a slot injector. Placement of liquid soil insecticides in
lines or slots' beside the row has not been accepted for two reasons.
First, knives operating in crop residues clog and become inoperable; may potentially uproot or prune corn plants (Chichester et al. 1984). The
second reason concerns the lack of economic justification to use root worm larvae thresholds (Foster and Tollefson, 1986) because current pes
ticide application machinery alternatives to prophylactic use of granu
lar soil insecticides is perceived as uneconomical (Weiss and Mayo,
1983).
The design of the slot injector consisted of two independently mounted fluted coulters (Model 2935, Yetter Manufacturing, Colchester,
IL 62326). Spring loaded arms were standard with each of the fluted coulters to allow operation on uneven surfaces. Also, depth gauge bands were mounted on each coulter to limit penetration to 3.8 cm (1.5 in).
The coulters were mounted 25.4 cm (10 in) apart and centered on the row.
The atomizers delivered a solid stream through a 0.00025 mm (0.0001 in) diameter orifice. In 1987, the slot injector was calibrated to deliver
375 L/ha (40 gpa) at 6900 kPa (1000 psi) while travelling at 3.2 km/h (2 mph). In 1988 and 1989 the slot injector was calibrated to deliver 187 64 L/ha (20 gpa) at 3450 kPa (500 psi); and ground speed was 4.8 km/h (3 mph). The nozzle orifices were placed approximately 4 cm above the soil and 2.0 cm behind the coulter. The pump was a stainless steel, triplex plunger pump (Model 311, Cat Pumps Inc., P. 0. Box 885, Minneapolis, MN
55440) that could operate at 14000 kPa (2000 psi) discharging a volume of 15 L/m (4 gpm) at 959 rpm. The pump was powered by a hydraulic motor coupled to the tractors hydraulic system.
The pesticides used in this study were: 1) chlorpyrifos (0,0-
Diethyl 0-3, 5, 6-trichloro-2-pyridyl phosphorothioate formulated as 15
G and 4E and sold under the trade name Lorsban by Dow Chemical U.S.A
(Midland, MI 48640); 2) Diazinon (0,0-Diethyl 0 (2-isopropyl-6 -methyl-
4-pyrimidinyl) formulated as a 14G and 4E and sold under the trade name
Diazinon by Ciba-Geigy (P.O. Box 18300 Greensboro, NC 27419); and
3) isazophos (0,0-Diethyl 0-(5-Chloro-l-(methyl)-1H-1,2,4 triazo-3-yl) formulated as a 10 G and 4E, sold under the trade name of Brace by Ciba-
Geigy ( P.O. Box 18300 Greensboro, NC). All granular formulations were applied at the rate of 1.12 kg (AI)/ha (1 lb/a) except isazophos which were applied at 0.74 kg (AI)/ha (0.661b/a) for both planting time and cultivation applications. Slot injection treatments were applied at two rates. The high rate was 1.12 kg (AI)/ha (1 lb/a) while the low rate was 0.37 kg (AI)/ha (0.33 lb/a) except for isazophos which was applied at 0.74 kg (AI)/ha (0.66 lb/a) instead of 1.12 kg (AI)/ha (1 lb/a).
Statistical analyses consisted of analysis of variance procedures for a randomized complete block design (SAS, 1982). Mean separations 65 were performed only if comparison wise F-tests were significant at the p=0.05 level. Mean separation was performed by the least significant
difference method (Cochran and Cox, 1957).
Dissolvable Pouch Study
Evaluation of water dissolvable pouches for containing soil insecti
cides was undertaken in 1988. Laboratory tests were designed to observe
the integrity of water dissolvable pouches of different materials hold
ing 28% N fertilizer. Two polyvinyl alcohol materials were used
(courtesy Gilbreath International and Royal Packaging, West Salem, OH).
Film thickness of two bag materials tested was 3.8 x 10"^ cm and 5.1 x
1 0 cm for QSA-2000 and QSA-2004 bags respectively. Bag dimensions were approximately 10 x 10 cm (4 x 4 in) and 20 ml chemical were added.
Filled bags were placed in a 250 ml (0.5 pt) jar and held under a fume hood with the fan operating for 3 months. At the end of the test pe
riod, bags were rated for integrity according to the following scale: 1
= no distortion, 2 ■= distortion but not leakage and 3 = rupture. A ran
domized complete block design was used with six replicates. Mean sepa
ration tests were performed on the datum determine if differences be
tween chemical and bags occurred. Mean separation was performed by the
least significant difference at the p=0.05 level of significance. 66
Total Control Costs
Total control costs are defined as the sum of total chemical control costs and total pesticide application machinery operation costs. First, chemical control costs were defined as $30/ha ($12/a) by Foster et al.
(1986) for application of 1.12 kg (AI)/ha (1 lb/a) for all soil insecti
cides. The 0.37 kg (AI)/ha (0.33 lb/a) rate was prorated to $10/ha ($4/
a) from the $30/ha ($4/a). However, to account for external costs, de
fined as costs which do not directly or indirectly benefit society as consequence of pesticide use (Pimentel and Levitan 1986), a misapplica
tion coefficient was used. The coefficient for granular applicators was
1.25 (Ellis, 1982) and the 1.02 error value was based upon data of Jasa
et al. (1986) for slot injectors. Thus, total chemical control costs
for granular applicators was $37.50/ha ($15/a) which included the
starter fertilizer cost of $0.37/ha ($0.15/ha) of while slot injection
at 1.12 kg (AI)/ha (1 lb/a) was $30.6/ha ($12.24/a), 0.74 kg (AI)/ha
(0.66 lb/a) rate was $20.19/ha ($8.08/a) and the 0.37 kg (AI)/ha (0.33
lb/a) rate was $10.09/ha ($4.04/a). Since some treatments included fer
tilizers the total chemical costs differed among treatments with and without fertilizers by $11.75/ha ($4.70/a). The application rate of
liquid fertilizers was 52.6 kg/ha (47 lb/a) actual N at 0.11 kg (AI)/ha
(0.10 lb/a).
Pesticide application equipment costs were calculated with the help of Caterpillar Tractor Companies software package, Equipment Investment 67 Analysis (EIA), (Reed et al. 1987). Six scenarios were defined and are
listed in Table 22. The six application machinery scenarios are: 1) planting time application with insecticide at 1.12 kg (AI)/ha (1 lb/a);
2) planting time applications without a soil insecticide; 3) slot injec
tion at 1.12 kg (AI)/ha (1 lb/a); 4) slot injection at 1.12 kg (AI)/ha
(1 lb/a) and fertilizer 52.6 kg (AI)/ha (47 lb N/a); 5) slot injection at 0.37 kg (AI)/ha (0.33 lb/a); and 6) slot injection at the rate of
0.37 kg (AI)/ha (0.33 lb/a) and fertilizer 52.6 kg (AI)/ha (47 lb N/a).
Calculation of fuel consumption, which is a required factor in EIA was
obtained by determining the draw bar pound pull (DBPP) of each implement
in the six scenarios. DBPP values were obtained from the Agricultural
Engineers Yearbook, Agricultural Machinery Management Data Section
D230.0 (Baxter and Hahn, 1983). Next, drawbar horse power pull (DBHP) was calculated according to the EIA program where DBHP is product of
DBPP and speed (miles per hour) divided by 375. Since DBHP varied with
the six scenarios of pesticide/fertilizer application and fuel consump
tion was obtained from the EIA program listing DBHP values for various
manufacturers tractors; slippage coefficient of of 2.7 was used to ob
tain a standard DBHP. This slippage coefficient was obtained for two
wheel drive tractors from the recommendation of the EIA program. Next
for a given slippage adjusted DBHP value for one of six scenarios, a
fuel consumption figure was obtained for 100% traction in a soft soil
condition. At best, fuel consumption required to operate the applica
tion equipment is a worse case scenario. Oil filter/grease costs were also required but were kept fixed at 50 cents/h while repair costs were defined as the hourly cost of repair/h parts. Repair costs were $4.00/h in wages and $1.50/h for parts. Total operator cost was $5/h while minimum operation cost for 1000 acres at 3.6 ha/h (9 a/h) was $555.
Fuel cost was $0.22/L (85 cents/gal). Tire costs were $4,500 for the granular bander and $4,000 for injectors. Depreciation was calculated on 20%, 15%, 10%, and 5% for years one through four. EIA provided a total operating cost of the pesticide application machinery, which was added to chemical control costs of six application machinery scenarios.
Results and Discussion
Field Studies 1987
At the Wooster site, insecticide x application method was signifi cant in conventional tillage plots in 1987. However, insecticide x ap plication method was not significant under no-tillage (F — 2.91, P <
0.0502, df = 6 , conventional tillage; F - 1.67, P < 0.1247, df = 6 , no tillage). At the Bluffton site in 1987, the insecticide x application method was significant (F = 2.98, P < 0.0486, df = 6). Therefore, con ventional tillage treatments are shown for both Wooster and Bluffton sites in Table 13.
Corn rootworm pressure was high at Wooster while the late planting date at Bluffton may have significantly reduced rootworm pressure as indicated by the untreated checks (Table 13). Diazinon injected at 1.12 kg (AI)/ha (1 lb/a), isazophos injected at 0.74 kg (AI)/ha (0.66 lb/a) and applied at planting were treatments with root ratings lower than any 69 others at the Wooster site. At Bluffton the similar observations were
made, isazophos applied at planting and injected at 0.74 kg (Al)/ha
(0.66 lb/a) along with planting time applications of chlorpyrifos were
treatments showing the best rootworm control. In nearly all cases at
both sites, cultivation treatments did a poorer job of rootworm control
except for treatments with diazinon at the Wooster site.
Field Studies 1988
Performance of soil insecticides in conventional tillage treatments
at the Wooster, Ohio site is shown in Table 14. In 1988 at the Wooster
site, insecticide X application method interactions were significant in
conventional tillage plots (F - 4.85, P < 0.0002, df = 6). The cultiva
tion applications of all soil insecticides were consistently lower than
other application methods except for treatments with diazinon, which out
performed the planting time application. Diazinon cultivation treat
ments were not significantly different from the 0.37 kg (AI)/ha (0.33
lb/a) injection application and planting time application of chlorpyri
fos. Only diazinon applied at the 1,12 kg (AI)/ha (2 lb/a) injection
rate provided significantly better control than the other applications
Chlorpyrifos applied at the 1.12 kg (AI)/ha (1 lb/a) injection rate
provided significantly better rootworm control than any other applica
tion method for chlorpyrifos. No significant differences were observed between the planting time application and 0.37 kg (AI)/ha (0.33 lb/a)
injected treatments chlorpyrifos. Although the planting time and 0.37 kg (AI)/ha (0.33 lb/a) injection application of isazophos and chlorpyrifos 0.37 kg (AI)/ha (0.33 lb/a) were not significantly different, the 0.74 kg (AI)/ha (0.66 lb/a) and
1.12 kg (AI)/ha (1 lb/a) injection applications of these respective compounds provided the best control of corn rootworm. The isazophos cultivation treatment, as previously stated, provided the poorest con
trol of rootworms.
Unlike 1987, significant differences were observed among the no-till
insecticide x application method treatments in 1988 at Wooster (F =
3.11, P < 0.0202, df = 6). The no-till soil insecticide application treatments of diazinon, in particular the planting time treatments were significantly less efficacious against rootworms than the injection treatments (Table 14). The cultivation treatments were omitted because these plots were under no-tillage conditions.
Chlorpyrifos injected treatments were significantly different. The
1.12 kg (AI)/ha (1 lb/a) rate provided better control than the 0.37 kg
(AI)/ha (0.33 lb/a) injection treatment. However, neither injection application treatment of chlorpyrifos was significantly different from the planting time treatment. Under no-tillage conditions, no signifi cant differences were observed among the application treatments of
isazophos. 71 Perusal of the check treatments shows that rootworm pressure was
greater in the conventional tillage treatments than the no-till treat ments. Further, with the exception of the cultivation checks, rootworm
damage was consistent in the conventional tillage and no-till plots.
Soil insecticide x application method interactions were significant
at the Bluffton site in 1988 for root rating (F = 3.03, P < 0.0296, df =
6) and yield (F = 10.28, P < 0.0001, df = 6). In Table 15, the perform
ance of the various soil insecticides demonstrated the cultivation
treatments were not as efficacious as any of the isazophos application
treatments at the Bluffton site. No significant differences were ob
served between the 1.12 kg (AI)/ha (1 lb/a) injection treatments of di
azinon and chlorpyrifos; also the 0.37 kg (AI)/ha (0.33 lb/a) injections
of diazinon and chlorpyrifos as well as the planting treatments. The
check treatments of the respective application methods showed little
variation, hence rootworm damage was fairly consistent.
Yield data from the Bluffton site (Table 15) shows the lowest yields
(bu/a) were in the checks while the highest yields were in the isazophos
injection plots. The next highest yield treatments were in the chlorpy
rifos injection treatments and diazinon 1.12 kg (AI)/ha (1 lb/a) injec
tion plots. Isazophos planting time application and both the 1.12 kg
(AI)/ha (1 lb/a) applications of diazinon injected and cultivated repre
sented the next grouping of soil insecticide treatments with respect to yield. F-values testing the significance of insecticide x application method interactions were significant for root ratings at the Western
Branch site in 1988 (F = 1.98, P < 0.0495, df = 3) and yield (F = 3.14,
P < 0.0129, df = 3). A summary of soil insecticide application method
tests at Western Branch site (Table 16) demonstrated little variation in
the performance of diazinon and chlorpyrifos with the exception of diaz
inon injected at 1.12 kg (AI)/ha (1 lb/a) with fertilizer and chlorpyri
fos injected at 1.12 kg (AI)/ha (1 Vo/a.) with no fertilizer which was
significantly better than the previously mentioned treatments. All
isazophos injection treatments except isazophos injected at 0.33 lb/a
with no fertilizer were not significantly different than chlorpyrifos
injected at 1.12 kg (AI)/ha (0.33 lb/a) with fertilizer.
In Table 16, highest yields were observed in the diazinon and
chlorpyrifos 1.12 kg (AI)/ha (1 lb/a) with fertilizer injection treat
ments and isazophos injected alone at 0.37 kg (AI)/ha (0.33 lb/a). Low
est yields for each insecticide at the Western Branch in South Char
leston, Ohio were as follows: diazinon applied at 0.37 kg (AI)/ha (0.33
lb/a) with fertilizer, 58.4 quintels/ha (94.2 bu); chlorpyrifos injected
at 1 lb/a without fertilizer (106.6 bu); and isazophos injected at 0.74
kg (AI)/ha (0.66 lb/a) without fertilizer (113.8 bu). This site was not
as adversely affected by the drought as indicated by the untreated
checks, hence response to fertilizer treatments was significant.
Insecticide x application method was significant in 1988 at the Mi
lan site for root rating (F = 4.12, P < 0.0127, df = 6) and yield (F = 12.03, P < 0.0004, df = 6). Table 17 is a summary of the soil insecti
cide application methods test at Milan site in 1988. The isazophos in jection application at 0.37 kg (AI)/ha (0.33 lb/a) and 0.74 kg (AI)/ha
(0.66 lb/a) with fertilizer ware the lowest root ratings and had some of
the highest yields. Chlorpyrifos injected at the rate of 0.33 lb/a with
fertilizer produced the highest yield of any insecticide treatment.
Diazinon injected at 0.37 kg (AI)/ha (0.33 lb/a) and 0.74 kg (AI)/ha
(0.66 lb/a) with fertilizer did not have significantly different yields
than the comparable application treatments of isazophos. Few differ
ences were observed between planting time treatments of all insecticides
except the significant differences in root rating between both chlorpy
rifos and isazophos with and without fertilizer. Yield differences for
planting time treatments occurred between isazophos with and without
fertilizer, while no differences in the diazinon and chlorpyrifos plant
ing treatments were observed. The checks for both root ratings and
yield were fairly consistent at the Milan site. Overall, the additional
application of fertilizer did not adversely affect the performance of
the soil insecticides, but these yield increases were not fully real-
lized due to the dry conditions at this site in 1988.
Field Studies 1989
In Table 18 are the efficacy results of the various soil insecti
cides under the two tillages at Wooster (F = 4.19, P < 0.0018, df = 6 conventional tillage; F = 2.77, P < 0.0478, df = 6 no-tillage). The conventional tillage checks were significantly different than all other 74 treatments except chlorpyrifos 15G at cultivation. The lowest root rat
ings were among both diazinon and isazophos treatments, except the asso
ciated planting time treatments. With the exception of chlorpyrifos,
the performance of cultivation treatments against rootworms was satis
factory for diazinon and isazophos. In no-till, the insecticide treat ments provided significantly better root protection than the checks.
Isazophos 4E injected at 0.74 kg (AI)/ha (0.66 lb/a) and chlorpyrifos 4E
injected at 0.37 kg (AI)/ha (0.33 lb/a) were significantly better than
isazophos, diazinon, chlorpyrifos planting treatments, diazinon injected
at 0.37 kg (AI)/ha (0.33 lb/a) as well as all checks.
The Western Branch insecticide x application method (F = 3.04, P <
0.0129, df = 6 root ratings; F - 3.12, P < 0.0405, df = 6 yield) ef
ficacy results are presented in Table 19. Rootworm pressure was moder
ate and variable among treatments in 1989 as depicted by the checks.
Also, all treatments demonstrated significantly greater rootworm control
than checks. All isazophos treatments provided significantly greater
rootworm control than chlorpyrifos treatments except isazophos injected
at 0.37 kg (AI)/ha (0.33 lb/a) without fertilizer. Both diazinon injec- ■;1 tion treatments with fertilizer were not significantly different than
any of the isazophos treatments. Apparently, the addition of fertilizer
52.6 kg (AI)/ha (47 lb/a) with diazinon resulted in lower root ratings;
better rootworm control. Although not significant all the time, the
addition of fertilizer improved rootworm control or improved the vigor 75 of the corn plant and bolstered the tolerance of the corn plant to root worm feeding damamge. In addition, significantly greater yields with the addition of fertilizer occurred in all insecticide treatments except the untreated check and diazinon injection treatments at 1.12 kg (AI)/ha
(1 lb/a). The highest yields were observed among the isazophos treat ments yet these were not significantly different from respective chlorpyrifos treatments. Diazinon treatment yields were not signifi cantly different from corresponding check treatments.
In 1989, significant differences were observed at the Milan site among insecticide x application method treatments (F = 12.24; P < 0.001, df = 6 root rating; F = 18.24, P < 0.0001, df = 6 yield). At the Mi lan site, severe rootworm pressure was common in 1989; 5's in the checks and only one of the treatments had a rating of 2 while the remainder was in the 3 to 4 rating range (Table 20). Untreated checks had signifi cantly higher root ratings than all treatments. Generally, planting time treatments displayed significantly less rootworm control for both isazophos and diazinon while chlorpyrifos countered this trend. Fur ther, isazophos and diazinon injection treatments displayed signifi cantly better root protection than either the untreated checks and chlorpyrifos treatments. This was apparent in the checks but the oppo site was observed among the yield results. The addition of fertilizer to both the isazophos and diazinon treatments demonstrated significant yield enhancement in the planting time treatments, however, although the enhancement was positive among the injection treatments, few instances of significance were observed. Significant differences in yield were observed with both application methods of chlorpyrifos at 1.12 kg (Al)/ ha (1 lb/a) rates with and without fertilizer. The use of fertilizer did not appear to help, but in several cases actually hindered rootworm control among diazinon and isazophos treatments although few significant differences were noted. Both isazophos and diazinon injection treat ments had significantly greater yields than any chlorpyrifos injection treatments despite the addition of fertilizer.
Dissolvable Pouch Study
Regardless of dissolvable pouch material, both fertilizers (28% N and triazone) ruptured and distorted the bags that contained them within three months (Table 21). No rupture or distortion was observed with any of the insecticides. Dissolvable pouches appear to be a feasible method to reduce pesticide exposure.
Worker exposure and waste management regulations now dictate a re duced exposure handling system as being practical for packaging of pes ticides. With increased concerns about regulating toxic waste dumps and ground-water contamination, the potential advantage of of a "no-waste container" will more than offset cost differences. Such systems, may in fact, be the only alternative (other than returnables) for professional custom operators, large chemical users, to successfully utilize future agricultural chemical tools. With a definitive match between use rates, 77 optimal formulations technology, and practical technology transfer in formation, these systems have the potential to dominate future packaging systems for at least the highly toxic pesticides in the years to come.
Total Control Costs
In Table 22, total chemical costs accounted for a large portion of the total operating cost of different insecticide application machinery scenarios. Total chemical costs were closely followed by fuel consump tion which was significant at bringing total operating costs of injec tion treatments to a third of the planting time application with insec ticides. Intuitively one might surmise machinery operation costs are fixed. Unfortunately, fuel consumption between a planter applying granular soil insecticides and another with empty hopper boxes is sig nificant. Not only is the weight reduction significant but the actual horse power attrition due to chain and belt operation of granule banders is also significant. Then, the probability of down time of a planter applying soil insecticide granules increases since the planting machin ery operation is more complex and vulnerable to mechanical failure. In addition, the planting operation alone reduces a significant portion of cost, namely soil insecticides. Therefore, the simplification of the planting operation is advantageous to the farmer since the consequences of planter down time are largely unknown. 78 However, injection costs were at least four times higher than a planter not applying a soil insecticide. Yet, the sum of the total op erating costs of a planter not applying a soil insecticide and slot ap plication machinery applying either soil insecticide at 1.12 kg (AI)/ha
(1 lb/a); 0.37 kg (A.I)/ha (0.33 lb/a) alone or in combination was re spectively 30 to 80 % the total operating cost of planting and applying a soil insecticide.
Summary
1) Slot injection application technology is not only comparable to the
contemporary application method of applying granules at planting
time, but in many circumstances was superior.
2) Isazophos planting and slot injection applications appeared to be
more consistent at reducing corn rootworm damage at both application
rates. Isazophos performed poorly as a cultivation treatment.
3) Diazinon cultivation treatments were consistent at controlling root
worms, less consistent was slot injection treatments at both rates
while planting time applications of diazinon provided poor rootworm
control.
4) Chlorpyrifos appeared to show the most annual variability in root
worm control regardless of application method. 5) Not only could rates be lowered, but the ability to achieve a rate
reduction of soil insecticides could only be brought about by an
accurate application method such as slot injection. Thus, we have
not seen reductions in the application rates of granular soil
insecticides.
6) User exposure which has become a topic of concern recently, may be
addressed more positively with liquid soil insecticide use. In
line injection from pesticide containers and water dissolvable
pouches are two promising technologies that will probably be
mandated as per an appropriate regulatory climate.
7) Simultaneous applications of soil insecticide with liquid fertilizer
may add value to not only the application machinery but the actual
insecticide-fertilizer application. In 1988, benefits of
simultaneously applying an insecticide and fertilizer were not
fully realized due to a drought. However, increased yields were
observed with the addition of fertilizer to insecticide application.
8) Consultants and custom applicators may see this as a excellent op
portunity to customize or fine tune agricultural chemical
applications. These two groups in the crop production system will
be looked to more frequently to apply agricultural chemicals as
the regulatory climate becomes more hostile to the small-medium
sized independent farmer. 80 9) Adoption of this machinery will be rapid if the fertilizer industry
promotes it, but a much slower pace of adoption will occur if the
onus is placed upon the pesticide industry. The agricultural im
plement industry will promote this machinery at a regional level due
to similiar differences in cropping practices. Therefore, the
short-line manufacturer that is relatively responsive will most
likely produce and market this machinery.
10) Further research needs to be done with new soil insecticide
chemistry, adaptability at different dates after planting or even on
planting machinery. 81
REFERENCES
Apple, J. W . , E. T. Walgenbach, and J. W. Knee. 1969. Northern corn rootworm by granular insecticide application at planting and cultivation. J. Econ. Entomol. 62:1033-1035.
Baker, D. B. 1985. Regional water quality impact of intensive row crop agriculture: A Lake Erie Basin Case Study. J. Soil Water Conserv. 40:125-132.
Balcomb, R. 1983. Secondary poisoning of red shouldered hawks with carbofuran. J. Wild. Manage. 47:1129-1132.
Baxter, J. F. and R. H. Hahn. 1983. Agricultural Engineers Yearbook of Standards 54:203-205.
Chichester, F. W . , J. E. Morrison and T. J. Gerik. 1989. Minimum disturbance fertilizer knifing for No-Till. Trans. ASAE 28:1013-1018
Clapp, J., M. K. Bergman, and L. W. Bledsoe. 1985. Evaluation of the nutiblast as a method for applying insecticide-urea solutions on continuous corn. Arcadian Technical Report N°. 12.
Ellis, C. R. 1982. A survey of granular application equioment and insecticide rates for control of corn rootworms. Proceedings of the Entomological Society of Ontario 113:29-34.
Erbach, D. C., J. J. Tollefson. 1983. Granular insecticide application for corn rootworm control. Trans. ASAE 10:696-699.
Foster, R. E., J. J. Tollefson, J. P. Nyrop and G. L. Hein. 1986. Value of adult corn rootworm population estimates in pest management decision making. J. Econ. Entomol. 79:303-310.
Graham-Bryce, I. J. 1983. Pesticide research for improvement of human welfare. Proceedings of the Fifth International Congress of Pesticide Chemistry 1:21-42. 82 Hall, F. R. and J. P. Reed. 1988. Implied biotargeting of soil applied pesticides. Application to Seeds and Soil, BGPG Monograph No. 39:351-361.
Jasa, P. J., E. C. Dickey and T. R. Peterson. 1986. Slot injection of herbicides. Appl. Eng. Agric. 30:42-51.
Kuhlman, D. K. 1984. Why soil insecticides don't work. Solutions 5:57-65.
Lilly, J. H. and H. Genderson. 1952. Fighting the corn rootworm. Iowa Farm Sci. 6:18-19.
Mayo, Z. B. 1976. Emergency post planting applications of insecticides to control larvae of the western and northern corn rootworm in Nebraska. J. Econ. Entomol. 69:600-602.
Mayo, Z. B. and L. L. Peters. 1978. Planting vs. cultivation time applications of granular soil insecticides to control larvae of corn rootworms in Nebraska. J. Econ. Entomol. 71:801-803.
McDonald, D. 1987. Chemicals and your health. Farm Journal 3:8-11.
Metcalf, R. L. 1986. Foreward, pp. vii-xv. In J. L. Krysan & T. A. Miller [eds.], Methods for the study of pest Diabrotica. Springer-Verlag, New York.
Miller A. 1987. Dimensionally stable water soluble pouches for safety. Eight Symposium on Pesticide Formulations and Application Systems. ASTM. IN PRESS.
Musick, G. J. 1974. Efficacy of liquid starter fertilizer combinations for control of resistant northern corn rootworm larvae. J. Econ. Entomol. 67:668-670.
Peters, D. C. 1975. Value of soil insect control in Iowa corn, 1951-1970. J. Econ. Entomol. 68:483-486.
Pimental, D. and L. Levitan. 1986. Pesticides: amounts applied and amounts reaching pests. BioScience 36:86-91.
Reed, J. P., F. R. Hall, H. R. Krueger and D. L. Reichard. 1988. An assessment of slot injected soil insecticides for corn rootworm control. Abstracts NCB-ESA, Denver, GO.
Reed, R. M., F. P. Gross, R. B. Fox and J. McManus. 1987. 1 2 ^ ed. Equipment investment analysis, Caterpillar Tractor Co. 1-56.
Reichard, D. L. and T. L. Ladd. 1983. Pesticide injection and transfer system for field sprayers. Trans. ASAE 26:683-686. Rider, A. R.; Dickey, E. C. 1982. Field evaluation of calibration accuracy for pesticide application equipment. Trans. ASAE 25:258-260.
SAS Institute. 1982. SAS user's guide: statistics. SAS Institute, Cary, N .C.
Solie, J. B., H. S. Witmus and 0. C. Burnside. 1983. Improving weed control with a subsurface jet injector system for herbicide. Trans. ASAE 27:1724-1728.
Spike, B. P. and J. J. Tollefson. 1988. Western corn rootworm larval survival and damage potential to corn subjected to nitrogen and plant density treatments. J. Econ. Entomol. 81:1450-1455.
Suett, D. L. 1988. Application to seeds and soil: recent developments, future prospects and potential limitations. In: Pests and Diseases. 2:823-832.
Thompson, A. R., H. R. Howse and G. W. Edmonds. 1988. Liquid insecticides and fertilizer treatments applied under seed at sowing: aspects of their performance and relevance to systems of reduced- input, sustainable agriculture. In: Pests and Diseases. 2:845-852.
Turpin, F. T. and J. M. Thieme. 1977. Impact of soil insecticide usage on coran production in Indiana: 1972-1975. J. Econ. Entomol. 71:83-86.
Urbain, C. D. 1989. EPA may ban Furadan. Farm Journal 3:29.
Whitehead, A. G. 1983. Application of pesticides to the seedbed be vertical band technique. Tenth International Congress of Plant Protection: Plant Protection for Human Welfare 2, 522.
Willson, H. R., B. Eisley and J. Lemon. 1987. Ohio pest management and survey program field scout methods handbook. Oh. Coop. Ext. Serv. GSI-1. Table 13. 1987 Wooster and Bluffton, Ohio. Soil insecticide application method efficacy test.
Root Ratings Treatments______Rate(AI)______Wooster______Bluffton
Diazinon 14G Planting 1.12 kg/ha (1 lb/a) 3.33 2.25 Diazinon 14G Cultivation 1.12 kg/ha (1 lb/a) 2.82 3.95 Diazinon 4E Injected 1.12 kg/ha (1 lb/a) 2.43 2.40 Diazinon 4E Injected 0.37 kg/ha (0.33 lb/a) 2.87 2.10
Chlorpyrifos 15G Planting 1.12 kg/ha (1 lb/a) 2.65 2.00 Chlorpyrifos 15G Cultivation 1.12 kg/ha (1 lb/a) 3.75 3.40 Chlorpyrifos 4E Injected 1.12 kg/ha (1 lb/a) 2.70 2.05 Chlorpyrifos 4E Injected 0.37 kg/ha (1 lb/a) 2.95 2.55
Isazophos 10G Planting 0.74 kg/ha (0.66 lb/a) 2.25 1.80 Isazophos 10G Cultivation 0.74 kg/ha (0.66 lb/a)4.15 3.45 Isazophos 4E Injected 0.74 kg/ha (0.,66 lb/a) 2.15 1.60 Isazophos 4E Injected 0.37 kg/ha (0. 33 lb/a) 2.45 2.10
Check Pooled 4.50 3.43
LSD (0.05) 0.30 0.50 Table 14. 1988 Wooster, Ohio. Soil insecticide application method efficacy test.
Root Rating
Treatments Rate (AI) Conventional No-Till
Diazinon 14G Planting 1.12 kg/ha (1 lb/a) 2.95 3.27 Diazinon 14G Cultivation 1.12 kg/ha (1 lb/a) 2.30 --- Diazinon 4E Injected 1.12 kg/ha (1 lb/a) 2.10 2.27 Diazinon 4E Injected 0.37 kg/ha (0.33 lb/a) 2.40 2.33
Lorsban 15G Planting 1.12 kg/ha (1 lb/a) 2.50 1.83 Lorsban 15G Cultivation 1.12 kg/ha (1 lb/a) 3.50 --- Lorsban 4E Injected 1.12 kg/ha (1 lb/a) 1.80 1.38 Lorsban 4E Injectted 0.37 kg/ha (0.33 lb/a) 2.65 2.22
Brace 10G Planting 0.74 kg/ha (0.66 lb/a) 2.65 1.61 Brace 10G Cultivation 0.74 kg/ha (0.66 lb/a) 3.45 --- Brace 4E Injected 0.74 kg/ha (0.66 lb/a) 1.85 1.55 Brace 4E Injected 0.37 kg/ha (0.33 lb/a) 2.55 1.66
Check Planting 1.12 kg/ha (1 lb/a) 3.55 3.33 Check Cultivation 1.12 kg/ha (1 lb/a) 3.15 --- Check Injected 1.12 kg/ha (1 lb/a) 3.50 3.11 Check Injected 0.37 kg/ha (0.33 lb/a) 3.60 3.38
LSD (0.05) 0.30 0 . 5 0 Table 15. 1988 Bluffton, Ohio. Soil insecticide application method efficacy test.
Yield Treatments Rate (AI) Root Rating Diazinon 14G Planting 1.12 kg/ha (1 lb/a) 4.85 27.7 Diazinon 14G Cultivation 1.12 kg/ha (1 lb/a) 5.25 40.2 Diazinon 4E Injected 1.12 kg/ha (1 lb/a) 4.70 50.8 Diazinon 4E Injected 0.37 kg/ha (0.33 lb/a) 4.95 40.5 Lorsban 15G Planting 1.12 kg/ha (1 lb/a) 4.40 28.9 Lorsban 15G Cultivation 1.12 kg/ha (1 lb/a) 5.15 35.5 Lorsban 4E Injected 1.12 kg/ha (1 lb/a) 4.55 61.1 Lorsban 4E Injected 0.37 kg/ha (0.33 lb/a) 4.95 58.4 Brace 10G Planting 0.74 kg/ha (0.66 lb/a) 4.35 39.4 Brace 10G Cultivation 0.74 kg/ha (0.66 lb/a) 5.35 31.5 Brace 4E Injected 0.74 kg/ha (0.66 lb/a) 3.75 79.2 Brace 4E Injected 0.37 kg/ha (0.33 lb/a) 4.30 78.7 Check Planting 1.12 kg/ha (1 lb/a) 5.15 28.3 Check Cultivation 1.12 kg/ha (1 lb/a) 5.60 24.0 Check Injected 1.12 kg/ha (1 lb/a) 5.10 38.0 Check Injected 0.37 kg/ha (0.33 lb/a) 5.45 27.7 LSD (0.05) 0.60 11.6 87 Table 16. 1988 Western Branch. Soil insecticide application method test. Yield Treatments Rate (AI) Root Rating (bu/a) Diazinon 4E Injected fert 1.12 kg/ha (1 lb/a) 3.66 143.2 Diazinon 4E Injected none 1.12 kg/ha (1 lb/a) 3.73 110.9 Diazinon 4E Injected fert 0.37 kg/ha (0.33 lb/a) 3.46 94.2 Diazinon 4E Injected none 0.37 kg/ha (0.33 lb/a) 3.80 106.6 Lorsban 4E Inj ected fert 1.12 kg/ha (1 lb/a) 3.60 134.0 Lorsban 4E Inj ected none 1.12 kg/ha (1 lb/a) 3.26 106.1 Lorsban 4E Inj ected fert 0.37 kg/ha (0.33 lb/a) 3.85 117.1 Lorsban 4E Inj ected none 0.37 kg/ha (0.33 lb/a) 3.86 113.4 Brace 4E Inj ected fert 0.74 kg/ha (0.66 lb/a) 3.26 128.9 Brace 4E Inj ected none 0.74 kg/ha (0.66 lb/a) 3.13 113.8 Brace 4E Inj ected fert 0.37 kg/ha (0.33 lb/a) 3.26 121.3 Brace 4E Injected none 0.37 kg/ha (0.33 lb/a) 3,80 144.3 Check fert 3.80 95.3 Check none 3.66 59.5 Check fert 3.86 54.4 Check none 4.46 59.5 LSD (0.05) 0.42 10.9 88 Table 17. 1988 Milan, Ohio. Soil insecticide application method efficacy test. Yield: Treatments Rate (AI) Root Rating (bu/a) Diazinon 14G plant fert 1.12 kg/ha (1 lb/a) 3.40 77.0 Diazinon 14G plant none 1.12 kg/ha (1 lb/a) 3.45 76.7 Diazinon 4E inject fert 1.12 kg/ha (1 lb/a) 2.45 93.5 Diazinon 4E inject none 1.12 kg/ha (1 lb/a) 3.10 71.3 Diazinon 4E inject fert 0.37 kg/ha (0.33 lb/a) 2.30 90.4 Diazinon 4E inject none 0.37 kg/ha (0.33 lb/a) 3.15 66.7 Lorsban 15G plant fert 1.12 kg/ha (1 lb/a) 3.40 85.4 Lorsban 15G plant none 1.12 kg/ha (1 lb/a) 3.80 83.7 Lorsban 4E inject fert 1.12 kg/ha (1 lb/a) 2.80 74.2 Lorsban 4E inj ect none 1.12 kg/ha (1 lb/a) 2.60 69.9 Lorsban 4E inj ect fert 0.37 kg/ha (0.33 lb/a) 2.65 128.5 Lorsban 4E inj ect none 0.37 kg/ha (0.33 lb/a) 3.15 83.6 Brace 10G plant fert 0.74 kg/ha (0.66 lb/a) 3.15 93.5 Brace 10G plant none 0.74 kg/ha (0.66 lb/a) 3.45 66.7 Brace 4E inj ect fert 0.74 kg/ha (0.66 lb/a) 1.75 103.2 Brace 4E inject none 0.74 kg/ha (0.66 lb/a) 2.30 76.4 Brace 4E inj ect fert 0.37 kg/ha (0.33 lb/a) 1.95 88.9 Brace 4E inject none 0.37 kg/ha (0.33 lb/a) 2.65 78.6 Check plant fert 1.12 kg/ha (1 lb/a) 4.00 87.4 Check plant none 1.12 kg/ha (1 lb/a) 3.80 35.5 Check inj ect fert 1.12 kg/ha (1 lb/a) 4.15 83.4 Check inject none 1.12 kg/ha (1 lb/a) 4.15 60.1 Check inj ect fert 0.37 kg/ha (0.33 lb/a) 3.75 60.0 Check inject none 0.37 kg/ha (0.33 lb/a) 3.95 70.6 LSD (0.05) 0.28 17.1 89 Table 18. 1989 Wooster, Ohio. Soil Insecticide application method efficacy test. Root Ratings Treatments Rate (AI) Conventional No-Till Diazinon 14G Planting 1.12 kg/ha (1 lb/a) 2.60 2.06 Diazinon 14G Cultivation 1.12 kg/ha (1 lb/a) 1.60 --- Diazinon 4E Injected 1.12 kg/ha (1 lb/a) 1.46 1.60 Diazinon 4E Injected 0.37 kg/ha (0.33 lb/a) 1.93 1.93 Lorsban 15G Planting 1.12 kg/ha (1 lb/a) 2.53 2.26 Lorsban 15G Cultivation 1.12 kg/ha (1 lb/a) 2.73 --- Lorsban 4E Injected 1.12 kg/ha (1 lb/a) 1.80 1.60 Lorsban 4E Injected 0.37 kg/ha (0.33 lb/a) 1.80 1.33 Brace 10G Planting 0.74 kg/ha (0.66 lb/a) 2.60 1.86 Brace 10G Cultivation 0.74 kg/ha (0.66 lb/a) 1.60 --- Brace 4E Injected 0.74 kg/ha (0.66 lb/a) 1.60 1.26 Brace 4E Injected 0.37 kg/ha (0.33 lb/a) 1.66 1.46 Check Planting 1.12 kg/ha (1 lb/a) 3.13 3.00 Check Cultivation 1.12 kg/ha (1 lb/a) 3.60 --- Check Injected 1.12 kg/ha (1 lb/a) 3.26 2.60 Check Injected 0.37 kg/ha (0.33 lb/a) 3.13 2.93 LSD (0.05) 0.48 0.49 Table 19. 1989 Western Branch, South Charleston, Ohio. Soil insecticide application method test. Yield Treatments______Rate (AI)______Root Rating (bu/a) Diazinon 4E injected fert 1.12 kg/ha (1 lb/a) 1.46 127.6 Diazinon 4E injected none 1.12 kg/ha (1 lb/a) 2.60 114.0 Diazinon 4E inj ected fert 0.37 kg/ha (0.33 lb/a) 1.80 128.3 Diazinon 4E injected none 0.37 kg/ha (0.33 lb/a) 2.60 113.3 Lorsban 4E injected fert 1.12 kg/ha (1 lb/a) 2.26 146.6 Lorsban 4E injected none 1.12 kg/ha (1 lb/a) 2.40 128.6 Lorsban 4E injected fert 0.37 kg/ha (0.33 lb/a) 2.20 145.6 Lorsban 4E injected none 0.37 kg/ha (0.33 lb/a) 2.20 126.3 Brace 4E injected fert 0.74 kg/ha (0.66 lb/a) 1.66 157.6 Brace 4E injected none 0.74 kg/ha (0.66 lb/a) 1.73 123.6 Brace 4E inj ected fert 0.37 kg/ha (0.33 lb/a) 1.33 149.3 Brace 4E injected none 0.37 kg/ha (0.33 lb/a) 1.80 128.6 Check fert 3.06 119.0 Check none 4.13 112.6 Check fert 2.66 145.0 Check none 4.26 101.6 LSD (0.05) 0.41 14.1 Q1 Table 20. 1989 Milan, Ohio. Soil insecticide application method efficacy test. Yield Treatments Rate (AI) _ Root Rating (bu/a). Diazinon 14G plant fert 1.12 kg/ha (1 lb/a) 4.75 104.3 Diazinon 14G plant none 1.12 kg/ha (1 lb/a) 3.50 129.3 Diazinon 4E inject fert 1.12 kg/ha (1 lb/a) 3.30 143.8 Diazinon 4E inject none 1.12 kg/ha (1 lb/a) 3.20 141.0 Diazinon 4E inject fert 0.37 kg/ha (0.33 lb/a) 3.75 136.8 Diazinon 4E inject none 0.37 kg/ha (0.33 lb/a) 3.20 149.3 Lorsban 15G plant fert 1.12 kg/ha (1 lb/a) 3.40 137.3 Lorsban 15G plant none 1.12 kg/ha (1 lb/a) 3.45 122.0 Lorsban 4E inj ect fert 1.12 kg/ha (1 lb/a) 3.75 126.0 Lorsban 4E inj ect none 1.12 kg/ha (1 lb/a) 4.45 109.8 Lorsban 4E inject fert 0.37 kg/ha (0.33 lb/a) 4.65 122.0 Lorsban 4E inj ect none 0.37 kg/ha (0.33 lb/a) 4.00 116.0 Brace 10G plant fert 0.74 kg/ha (0.66 lb/a) 4.20 140.5 Brace 10G plant none 0.74 kg/ha (0.66 lb/a) 4.25 122.0 Brace 4E inject fert 0.74 kg/ha (0.66 lb/a) 3.20 153.0 Brace 4E inject none 0.74 kg/ha (0.66 lb/a) 3.20 144.0 Brace 4E inj ect fert 0.37 kg/ha (0.33 lb/a) 4.10 134.5 Brace 4E inject none 0.37 kg/ha (0.33 lb/a) 2.90 128.0 Check plant fert 1.12 kg/ha (1 lb/a) 5.70 105.0 Check plant none 1.12 kg/ha (1 lb/a) 5.15 88.3 Check inject fert 1.12 kg/ha (1 lb/a) 5.50 102.0 Check inj ect none 1.12 kg/ha (1 lb/a) 5.05 97.0 Check inj ect fert 0.37 kg/ha (0.33 lb/a) 5.40 103.3 Check inj ect none 0.37 kg/ha (0.33 lb/a) 5.60 83.3 LSD (0.05) 0.59 12.6 92 Table 21. Summary of three month evaluations for dissoluble pouch integrity. Agrichemical Bag Material______Rating Chlorpyrifos QSA 2000 1.00 a Diazinon QSA 2000 1.00 a Isazophos QSA 2000 1.00 a 28% N QSA 2000 3.00 c Triazone QSA 2000 1.50 b Chlorpyrifos QSA 2004 1.00 a Diazinon QSA 2004 1.00 a Isazophos QSA 2004 1.00 a 28% N QSA 2004 3.00 c Triazone QSA 2004 2.00 b LSD (0.05) 0.92 Table 22. Drawbar pounds pull (DBPP), drawbar horsepower pull (DBHP), fuel consumption, total chemical costs and total operating costs for six scenarios of rootworm insecticide application machinery operation. Application Machinery Scenario DBPP DBHP Fuel Consumption Total Chemical Cost Total Operating Cost Planting Insecticide^ 3750 162.0 4.2 L/h(17.7 gal/h)~ $37.50/ha($15.00/a) $43.00/ha($17.20/a) Planting w/ no Insecticide 2160 90.07 2.57L/h(10.9 gal/h) 3.95/ha(l.58/a) Inj ection Insecticide^ 300 12.96 1.95L/h(8.3 gal/h) 30.55/ha(12.22/a) 29.65/ha(ll.16/a) Injection Insecticide^ 300 12.96 1.95L/h(8.3 gal/h) 42.90/ha(17.18/a) 33.90/ha(13.56/a) + Fertilizer^ Inj ection Insecticide^ 300 12.96 1.95L/h(8.3 gal/h) 10.16/ha(4.06/a) 13.50/ha(5.40/a) Injection Insecticide^ 300 12.96 1.95L/h(8.3 gal/h) 11.75/ha(4.70/a) 15.09/ha(6.04/a) + Fertilizer^ Total production is 3.6 ha/hr(9 a/hr) at 6.4 km/hr(4 mph) with an effective operating width of 6 m (18 ft). ^ Insecticide rate 1.12 kg (AI)/ha (1 lb/a) for chlorpyrifos and diazinon; 0.74 kg (AI)/ha (1 lb/a) isazophos. ^ Insecticide rate 0.37 kg (AI)/ha (0.33 lb/a). ^ Fertilizer rate 52.6 kg (AI)/ha (47 lb/a). Figure 1. Slot injector developed at the Laboratory for Pest Control Application Tecnology, The Ohio Agricultural Research and Development Center Wooster, Ohio 44691 (Hall and Reed 1988, Reed et al. 1988). Figure 2. Skid injector of Clapp et al. (1985); Lower lefthand corner, close-up of a countersunk nozzle mounted to a skid plate. Note the fine stream produced by this nozzle, soil penetration is limited. Figure 3. Point injector developed by Baker (1985) used to inject liquid fertilizer at last cultivation. Note depth is regulated by length of spoke and diameter of rim. OHIO SOIL REGIONS iflLUFFT! I. High Lime Glacial Lake Sediments II. Fine-Textured High Lime Glacial Drift III. Med.-lextured High Lime Glacial Drift IV. lllinoian Glacial Drift V. Low Lime Glacial Lake Sediments VI. Low Lime Glacial Drift VII. Sandstone and Shale VIII. Limestone and Shale Figure 4. Sites used to represent soil regions throughout Ohio. (1981-82 Agronomy Guide, Ohio Cooperative Extension Service. B472) 1 0 C H A P T E R I V ESTABLISHMENT OF AN ACTION THRESHOLD FOR LARVAL CORN ROOTWORM CONTROL AND A COST/BENEFIT ANALYSIS OF SOIL INSECTICIDE APPLICATION MACHINERY Introduction Concurrent to the evolution of agriculture from a family tradition to an extremely competitive business, the science of applied entomology experienced a change in emphasis and direction over the past twenty-five years. In addition, disciplines of crop protection and plant pest management have evolved in fairly recent times. Unfortunately, the earliest development of pest control tactics, especially synthetic organic pesticides, were embraced feverishly and often employed without regard to financial returns or environmental contamination. Plant pests do not differentiate between various effects that ultimately influence crop yield and grower incomes. However, crop protection practitioners such as economic entomologists can quantitatively determine the effects of insect pests on a given crop. Therefore, the general concept of Economic Threshold (ET) was defined as the density at which control measures should be determined to prevent an 98 99 increasing pest population from reaching the economic injury level. The Economic Injury Level (EIL) is further defined as the lowest pest population density that will cause economic damage that is equal to the cost of control. In summary, the added cost of pest control should be equal to or less than the added benefits of that control (Horn, 1988). The western and northern species of corn rootworm together are the most important pests of corn in the North Central States. It has been estimated that approximately half of the corn acreage in the United States has a soil insecticide applied annually for rootworm control (Metcalf, 1986) , which is worth approximately $1 Billion, currently more than the cost for controlling the remaining insect pests of corn. Corn rootworms can be effectively controlled by crop rotation, but this option is utilized on less than fifty percent of corn acreage (Metcalf, 1986). The primary means of rootworm control in continuous corn is the use of granular insecticides applied at planting time either in or banded over seed furrows. There are several major reasons why decreasing soil insecticide applications is critical at this point in time. Record low rates of return on grain production necessitates that production costs, including insecticide usage, be critically evaluated for profitability. There is a growing concern that the carbamate and organophosphate insecticides used for rootworm control are increasingly prone to accelerated degradation by soil inhabiting microorganisms (Reed et al. 1987). Long 100 term continuous use of soil applied insecticides appears to increase the rate at which accelerated degradation occurs (Reed et al. 1989). The concern is that if soil applied insecticides are used when it is not absolutely necessary, the toxicants efficacy will be significantly reduced when a severe problem with rootworms is encountered (Metcalf, 1980). Growing concern for the environmental fate of soil applied insecticides for their potential to contaminate water resources as well as reports of non-target poisonings (ie. bird and fish kills) have contributed to negative perception of all pesticides. This trend is not new, but has been the impetus for governmental regulation of pesticide use and development. Without a doubt, the time had come for a compromise between indiscriminate use of pesticides and no use at all. Stern et al. (1959) provided such a compromise when they introduced the concept of integrated control. They suggested the judicial use of all available control tactics on an "as needed" basis and predicted that crop yields could be maintained or even increased with the proper management of insect pests. These early concepts were later expanded to include many pest types (viz., plant pathogens, weeds, and insects), and the theme of integrated pest management (IPM) was adopted. Certain aspects of IPM could be modified into objective economic guidelines while incentives for pest management slowly changed from reducing pesticide use, per se, to reducing financial inputs to the farm. Although IPM embraces the concepts of ET and EIL, it is appropriate to ask whether this tenant is practical. The answer must be qualified. 101 How feasible it is depends on the value of the expected loss relative to the cost of the controls, how variable control efficacy is, and how effective and costly it is to gather information on the incidence of the pest. If efficacy of controls is variable but the frequency of the conditions leading to this variability can be estimated, it is possible to devise economic thresholds that maximize expected net returns. Treat-when-necessary scenarios are a basic tenant of IPM programs but are not currently used for managing rootworm damage in corn due to lack of application machinery that can meter timely insecticide applications (Weiss and Mayo, 1983). A major problem in implementation of a rootworm IPM program has been the lack of accurate prediction of rootworm damage potential prior to the planting of corn and application of insecticides. Foster et al. (1986) concluded that prediction of damage from adult counts was so poor that the optimal strategy for managing corn rootworms in Iowa was not to sample adult populations at all and to always treat corn following corn with a soil insecticide. Foster et al. (1986) acknowledged that their conclusions would change if the ability to predict subeconomic damage was improved. Therefore, prophylactic planting time applications of soil insecticides are viewed by many as merely insurance. Risk of crop loss has been theoretically minimized, although in reality this does not occur all the time. Correspondingly, the value of annual use of a soil insecticide is viewed by some as a poor investment (Turpin and Thieme, 1974). 102 Separate from the development of IPM, techniques in risk management were developed by agricultural economists to provide production or marketing strategies when knowledge about future events was less than perfect. Knight (1921) was one the earliest workers in the area of risk management and first divided decision-making strategies onto risk and uncertainty. He defined the risk situation as one in which the decision-maker has less information about the alternative outcomes and their probability of occurrence. Modern decision theory recognizes that the objective probabilities required by traditional analysis for risk seldom, if ever, exist. In pest management situations, entomological research may provide more guidance or confidence in formulating and utilizing probabilities in reducing risk. One neglected factor in the corn rootworm management scenarios is the actual market price for corn. This in turn influences the ET and « EIL. Unfortunately, three serious assumptions flaw current rootworm management strategies. The first is the inflexibility of market price. Several papers dealing with economic thresholds for rootworms whether they are based upon sampling for adults, eggs or larvae have accepted $12.00/quintel ($3.00/bu) (Foster et al. 1986; Stamm et al. 1985; and Apple et al. 1977). Unfortunately, the $3.00/bu is neither the mean nor median market price but is a substantially higher and unrealistic statistic (USDA-ERS, 1989). Next, not only is the quoted price figure in doubt, but the concept of maximization of pest control strategy is undermined since the higher end of commodity price spectrum is used. In 103 reality, the control measure may not equal the monetary benefits of a high price base when low price bases are predominant especially later in the season. Thus, the percieved incremental increase in yield, income may be less than the actual cost to treat. Last, substantiating any rootworm threshold in the literature has required the employment of uneconomical sampling schemes to obtain significance at p = 0.05 level of probability. When sampling costs are calculated, no account is made to lower the p-value (accuracy) to show at what level sampling is economical (Bergman et al. 1984). Therefore, uncertainty of commodity (corn) prices at time of treatment, namely planting is more realistic than a preventive approach for which no comparison to substantiate the decision can be made. Hence, no history or data base is established that can reflect risk, for future decisions. However, such risk is reduced over time if and only if a larval sampling scheme and efficacious treatment methods are employed (Petty and Kuhlman, 1972). Otherwise, no due course to avert losses and at the same time reduce costs of rootworm control may be achieved should planting time applications fail to control rootworms. In addition to the uncertainty of rootworm population growth, the associated damage may not correspond due to external variables such as weather, soil types and so on. Finally, although health of the plant may be affected, this may not be proportional to a given level of damage that will affect yield (Turpin, Dumenil and Peters, 1972). 104 All of this suggests that although prophylactic, planting time applications of soil insecticides appear to avert risk and are viewed as maximizing returns, actually could cost more than what they are worth. External costs of soil insecticide use are not addressed, nor is there any indication in reducing them with preventative, prophylactic applications of soil insecticides at planting. First, the use of future prices of commodities at time of deciding whether to treat or not treat could be implemented into corn rootworm IPM programs. The uncertainty of knowing the actual rootworm population and damage levels poses the question of outcomes and penalties associated with a wrong decision. Second, at the time of scouting for damage by rootworm larvae, a real-time based decision could be made, provided larval thresholds and sampling schemes exist. Third, in earlier work by Mayo and Peters (1978), soil insecticides with limited field lives were more efficacious at cultivation than planting applications. Unfortunately, the control obtained was more variable than that of planting time application. Further, work by Hall and Reed (1988) demonstrated soil insecticide application rates may be reduced by 66% without compromising rootworm control using a slot injector (Figure 1). Thus, external costs may also be reduced. Adult and egg mortality factors would not interfere with the decision process since actual numbers of larvae that are causing damage are counted. Naranjo and Sawyer (1988) indicated that gravid, adult female rootworm counts should improve predicting damage over total 105 rootworm counts. Unfortunately, the labor requirements associated with the sampling scheme for rootworm adults in lieu of pheromone trapping (Karr and Tollefson, 1987) do not appreciably overcome the loss of accuracy associated with mortality factors. Further, implications about the role of N with respect to root proliferation by rootworms is more important than root size in the survival of larvae (Branson et al. 1982). This is just another factor that could drastically alter the meaning of adult rootworm counts for use in predicting future rootworm damage. However, if larval counts are obtained along with a preliminary root rating, this would insure that the variables of N levels and root regeneration are addressed. Therefore, the use of economic thresholds based upon the actual larval counts using an economic sampling scheme (Weiss and Mayo, 1983; Morris, 1960) and simultaneously performing a preliminary root rating as described by Hills and Peters (1974) with slot injection machinery for applying soil insecticide should be considered for corn rootworm integrated pest management (Hall and Reed, 1988; Reed et al. 1987; Thompson et al. 1988). There are two objectives that need to be addressed concerning the use of slot injection machinery. The first objective addresses the determination of an approximate economic threshold of rootworm larvae based upon a larval sampling scheme with a pretreatment root rating that is scout friendly. Decision making to treat or not treat would be based upon the real market value of the corn crop (ie. futures prices). The second objective would compare scouting and prophylactically applying a 106 soil insecticide at time of last cultivation with planting time applications. This would define or perhaps justify either treatment scheme under a variety of economic conditions. Materials and Methods Three sites throughout Ohio (Bluffton, Milan, and Western Branch) selected for this study were located in Western Ohio with specific soil types indicative of the Midwest (Figure 4). A randomized complete block design was replicated four times at each site in 1988 and 1989. A complete listing of each site's edaphic factors, root rating and pre-application larval count dates as well as yield collection dates are presented in Table 39. Scouting Costs A modified version of the larval sampling scheme of Bergman et al. (1981) was used. Five corn plants were dug at random from each treatment replicate. Each plant was violently shook once close to the ground. Larvae were counted in both the shook soil substrate and the root mass, Weiss and Mayo (1983) concluded that differentiation between second and third instars, which are the most visible stages of rootworm, was practically impossible in the field. Therefore, rootworm larval counts represented a pooling of only second and third instars to facilitate a scout friendly sampling method. Next, the root mass was rated according to the Iowa 1-6 root rating scale (Hills and Peters, 1974). All larval sampling and root rating was done after June 1 and 107 through V6 stage of corn (Ritchie and Hanway, 1982). This data represents the approximate total of both northern and western corn rootworms in Ohio (Clement and McCartney, 1987). Since clumped distributions, synonymously known as negative binomial distribution commonly describe insect populations, confirmation of rootworm larvae fitting the negative binomial distribution was performed by a maximum likelihood procedures statistical package (Ross, 1980). A chi-square value at p = 0.05 level of significance was compared with the calculated chi-square to determine whether or not the negative binomial distribution is biologically significant (Horn, 1988). Calculating the cost of scouting requires the establishment of a level of accuracy. The index of aggregation often termed "K", is required for determining the accuracy of a sampling scheme. The value of K is influenced by the size of the sampling unit and also the number of samples because the variance is used in its calculation (Equation 3-1) (Horn, 1988). K = x^/s^ - IT Equation 3-1 Where K = the index of aggregation, "x is the mean and s^ is the variance of the sample population. Next, accuracy was determined for each site and year according to Equation 3-2 (Rojas, 1964). The level of accuracy can be related to the number of samples, especially for a negative binomial distribution. n - (1/x + 1/K)/A^ Equation 3-2 Where n equals the number per unit sample, x is the mean, K is the index of aggregation, and A is the desired level of accuracy. Once the desired level of accuracy was determined and the required number of samples computed, cost valuation was computed using Equation 3-3 (Horn, 1988). C = T x N X W Equation 3-3 Where C equals cost, T is defined as the time per unit sample (plant), N is the number of samples per unit area and W equals the hourly wage of the scout. Establishment of Damage per Insect (Rootworm Larvae) The relationship between first larval counts or root ratings and yield was established by the analysis of covariance (ANCOVA) using SAS PROC GLM and PROC REGRESS (SAS, 1982). This relationship was determined separately for years 1988 and 1989. Regression analysis comparisons for 109 single line, parallel lines and equivalent slopes were performed on larval counts taken after planting time treatments but before injection and cultivation applications were made at Bluffton, Western Branch and Milan sites referred to as larval counts and root rating. In 1989, Bluffton was omitted. Since scout friendly, economical insect sampling methods tend to compromise accuracy, the accuracy level in this study was 70% which compliments a 30% level of significance. These analyses were performed to determine whether larval counts or root ratings should be the primary criterion to predict damage at the p = 0.30 level. Hence, a decision to treat could be based upon a scout friendly method, as used in this study. Regression analysis for single regression, parallel lines and equal slopes established whether regressions were significantly different between sites for a given year. Intercepts indicated the maximum yield at a site while slopes represented the amount of damage per rootworm larvae, as observed in the untreated check plots. Cost Benefits Analysis ANCOVA was performed on all insecticide treatments at the respective sites and years to obtain regressions expressing the relationship between first larval count and yield. As previously stated, economic threshold of rootworm larvae is two larvae per plant. Yields from both the untreated check and treatments were calculated with two larvae. To obtain a gain/loss for the particular treatment, untreated plot yields were subtracted from treated plots. This value was multiplied by a 110 market value of $10/quintel ($2.5/bu) to obtain economic benefit of that particular treatment. The cost/benefit ratio was calculated from the total operation cost in Table 22 (Chapter III) for a particular application method (ie. planting, injection) and the previously calculated benefit value of a particular insecticide treatment. Essentially, the quotient of total operation costs and insecticide treatment-benefit value for a particular soil insecticide applied by a specific application method was determined for prophylactic or no scouting costs in the operation costs. When scouting costs $10.00/ha ($4.00/a) were added, this provided the basis of cost-benefit scenarios for treatment in an IPM program. Cost/benefit ratios were determined only for the Western Branch and Milan sites since both sites had two years of yield data. Results and Discussion Scouting Costs Bergman et al. (1983) described most rootworm larval populations as clumped or fitting the negative binomial distribution. Our findings also indicated that rootworm larvae populations fit the negative binomial distribution at all respective sites in 1988 and 1989 (Table 23 and 24). This not only demonstrated the sampling method was adequate but also allowed the cost of sampling to be calculated for a given level of accuracy or significance. Table 25 is a comparison between sample numbers for different levels of accuracy at the respective sites and Ill years. In 1989, approximately seven times as many samples were required to attain the same level of accuracy in 1988 at the Western Branch and Milan sites. Scouting costs reflected these seasonal differences between 1988 and 1989 in Table 26. This would suggest that the rate of return might be greater in years of environmental stress. Such a conservative approach would allow the decision to treat or not treat be based upon commodity prices later in the season which have less uncertainty than early season commodity prices. Establishment of Damage per Rootworm Larvae ANCOVA demonstrated regressions of the first larvae counts to predict yields were highly significant in 1988 and 1989 (Table 27 and 28). Indeed, the significance levels were well within the p = 0.3 values that were arbitrarily chosen as the most economical larval sampling scheme. However, significance of parallelism tests between sites indicated that slopes were equal while intercepts were not. Therefore, the level of damage per rootworm larvae is the same regardless of site for a given year as indicated by equivalent slopes. Mean yield loss per larvae was 3.58 and 9.79 quintel/ha (2.24 and 6.12 bu/a) for 1988 and 1989 respectively. Mean maximum yield in untreated checks was 75.39 and 111 bushels per acre for 1988 and 1989 respectively. Therefore, a 2.97 and 5.51 percent yield loss per larvae was calculated for 1988 and 1989 respectively. Conservatively, two larvae/plant using a scout friendly sampling scheme cost Ohio corn producers a minimum of $ 37.50/ha ($15/a) at $ 10/quintel ($2.5/bu). 112 Damage per larvae as indicated in this study concurs with a two larvae threshold limit that has been established by Purdue University extension entomologists (Edwards and Turpin, 1988). However, the yield potential of an individual site differed significantly as indicated by the intercepts. Early root ratings were not significant in accurately predicting yield in either 1988 or 1989 (Tables 27 and 28). Our findings agree with Turpin, Dumenil, and Peters (1971) that agronomic and edaphic factors can drastically alter the yield potential and perhaps mask the stress effects of rootworm larvae feeding and subsequent yield loss. Further, Ruppel (1984) questioned the exclusion of crop tolerance estimates in calculating a true percent control value of insect pests. Branson et al. (1982) explained differences in susceptibility to corn rootworm feeding of inbred corn lines as tolerance. However, the significance levels of larval sampling for larval count to yield regressions in 1988 substantiates the effects of the 1988 drought. Our results agree with Spike and Tollefson (1988) that under years of high moisture stress, effects of rootworm larvae feeding damage is primarily due to loss of turgor. However, in wet years and high fertility, yield loss may be greater due to a combination of larger larval populations, inter-plant competition for nutrients and water as well as greater incidence of soil and foliar plant pathogens. Further, the species composition of the rootworm population was unknown due to the difficulty of larval identification in the field. Moreover, Gray and Tollefson (1987) concluded northern corn rootworms were less 113 capable of causing root damage than western corn rootworm larvae. An analysis of corn yields in Minnesota over a 50 year period determined northern corn rootworms accounted for a 3% yield reduction. However, after the establishment of western corn rootworm, yield reductions increased to 11% (Lockertz et al. 1980). Cost/Benefit Analysis Interpretation of cost/benefit analyses is used by individuals in crop protection to determine the 'value' of a particular treatment. The term 'value', calculated from many sources of information is usually implicated in a positive tone. However, the meaning of value in this analysis will be neutral. Prophylactic soil insecticide use is defined as no scouting or always treating. On the other hand, scouting values took into account total operation costs plus scouting costs. Scouting costs may be viewed as the worse case scenario while deciding to not treat would be a further benefit both environmentally and economically. Cost/Benefit Analysis without Fertilizer - Milan Site Comparison of cost/benefit ratios of soil insecticide applications without fertilizer application are presented in Table 29. In 1988, planting treatments had the lowest cost/benefit ratios regardless if application was done prophylactically or scouting was performed (ie. 114 adult counts the previous fall). Chlorpyrifos appeared to be the most costly planting time treatment to control rootworms (Table 29). The 1.12 kg (AI)/ha (1 lb/a) slot injection treatments were the most costly rootworm control treatments. Even if scouting was performed, and treatment was deemed unnecessary, the cost/benefit ratio demonstrated a financial loss would be incurred. However, the 0.37 kg (AI)/ha (0.33 lb/a) injection treatments indicated a more positive result of these treatments. Isazophos treatments were financially the most rewarding, while chlorpyrifos and diazinon were somewhat equal. Scouting, then deciding to treat or not treat with the 0.37 kg (AI)/ha (0.33 lb/a) injection treatments was economical. In 1989 cost/benefit analyses at the Milan site were much different than 1988. Not only were cost/benefit ratios lower on all applications, but benefits could be obtained with any of the treatments. Prophylactic planting time chlorpyrifos and diazinon treatments were more beneficial than isazophos treatments. However, when scouting was performed, isazophos cost/benefit ratio was below chlorpyrifos and diazinon planting time treatments. Injection treatments at 1.12 kg (AI)/ha (1 lb/a) behaved in economically similar fashion as planting time treatments. More important, however, are the benefits of scouting in conjunction with this treatment; for example scouting, then deciding to apply an insecticide could be economically favorable. Of the insecticides, 115 chlorpyrifos had the highest cost/benefit ratio 0.39 and 0,54, with and without scouting respectively. Cost/Benefit Analysis with Fertilizer - Milan Site The slot injection treatments at 0.37 kg (AI)/ha (0.33 lb/a) behaved in a similar fashion to the 1.12 kg (AI)/ha (1 lb/a) slot injection treatments that were prophylactically applied at Milan in 1989 (Table 29). Application of urea fertilizer at 52.6 kg (AI)/ha (47 lb/a) with various insecticide-application treatments at the Milan site in 1988 is presented in Table 30. In general, 1.12 kg (AI)/ha (1 lb/a) planting time or injection treatments whether scouted or prophylactically treated had extremely high cost/benefit ratios, indicated significant loss. However, cost/benefit ratios were favorable for both scouting and prophylactically treating at the 0.37 kg (AI)/ha (0.33 lb/a) injection rates for chlorpyrifos and isazophos. Scouting costs caused the diazinon 0.37 kg (AI)/ha (0.33 lb/a) injection treatments to become uneconomical (cost/benefit ratio = 1 .01). In 1989, soil insecticide applications with fertilizer at the Milan site were more economical, generally speaking through 1988. However, differences were seen among insecticides for a given application method scenario. Specifically and regardless of prophylactic and scouting scenarios the following treatments had cost/benefit ratios greater than 1 were planting time diazinon treatments and 0.37 kg (AI)/ha (0.33 lb/a) chlorpyrifos treatments. Again, scouting appeared to be beneficialI 16 in all other scenarios. Cost/Benefit Analysis without Fertilizer - Western Branch At the Western Branch site in 1988, regardless of prophylactic application or scouting, chlorpyrifos applications were uneconomical at 1.12 kg (AI)/ha (1 lb/a) rate of injection (Table 31). In addition, isazophos was not economical if applied at the 0.74 kg (AI)/ha (0.66 lb/a) rate after scouting. 1989 results show an entirely different situation than 1988. Only the 1.12 kg (AI)/ha (1 lb/a) chlorpyrifos and isazophos treatments after scouting were uneconomical, although approaching equivalency, the cost/benefit ratios of diazinon and chlorpyrifos 0.37 kg (AI)/ha (0.33 lb/a) treatments were still economically advantageous. Cost/Benefit Analysis with Fertilizer - Western Branch Cost/benefit ratios of various soil insecticide application treatments with fertilizer at the Western Branch site in 1988 are presented in Table 32. Only isazophos either prophylactically applied or applied after scouting was economical to inject at 0.74 kg (AI)/ha (0.66 lb/a) with 52.6 kg N/ha (47 lb/a). However, all soil insecticide injection treatments at 0.37 kg (AI)/ha (0.33 lb/a) with 52.6 kg (AI)/ha (47 lb/a) of fertilizer were economically justified, especially the scouting applications. In 1988, none of the 1.12 kg (AI)/ha (1 lb/a) 117 applications of insecticides and fertilizer 52.6 kg (AI)/ha (47 lb/a) were economical. However the 0.37 kg (AI)/ha (0.33 lb/a) injection treatments were all economical to apply. Scouting, again was promising, demonstrating that a treat, no-treat scenario was advantageous. Other crop protection disciplines such as weed science and plant pathology have also considered the total cost approaches of benefits assessments and in their analyses included different pesticide application methods (Cashman et al. 1981, Jordan and Stinchcombe, 1988, Stemerhof et al. 1988). Indeed, the need for including total machinery operation costs has not been addressed by economic entomologists (Foster et al. 1986, Peters, 1975, and Turpin and Thieme, 1977). Nor has there been any inclusion of other economic analyses of other crop protection disciplines to justify scouting (Wearing, 1988). No other economic entomological study has defined total machinery, external and scouting costs along with an economic threshold to establish a cost/benefit ratio for a particular soil insecticide and application treatment. Comparisons between pesticide application techniques such as planting time application of granular compounds and slot injection of liquid formulations was performed to demonstrate the importance of not relying on a specific application technology. The agricultural chemical industry has the unique opportunity to actually go on the 'offensive' by adopting alternative application technologies which are both environmentally and economically favorable. Slot injection is an application technology that has enormous implications 118 throughout the U.S. cornbelt. Loss of several granular soil insecticides has been perceived as having dire consequences to corn producers (Osteen and Kuchler, 1986). The transistion between the loss of several or even one key agricultural chemical and adoption of alternatives and refinement of their use has been theorized by many experts as difficult and costly. Indeed, cotton producers have witnessed that the loss of one compound, chlordimeform, has cost the American public $148 million annually. If resistance management is not implemented (chlordimeform is a synthetic pyrethroid synergist) with new thresholds for less effective cotton insecticides, both consumer and cotton producer could lose $852 million (Osteen and Suguiyama, 1988). Summary 1) Rootworm larvae populations fit the negative binomial distribution which allows sampling costs for a given level of accuracy to be calculated; at 70% accuracy,the cost of sampling is $4.10/ha ($1.60/a). However, a sampling cost of $10.00/ha ($4.00/a) would reflect a more realistic value using a scout friendly method. 2) An economic threshold for larval sampling of corn rootworms in Ohio is a mean of 2 larvae per plant, sampling after June 1 through V6 growth stage of corn with 70% accuracy. Such a sampling scheme could be used in conjunction with futures prices and knowledge of attainable yields to decide whether to treat or not treat. 119 3) Use of preliminary root ratings as recommended by Hills and Peters (1971) is not accurate enough for even an economical sampling scheme. Thus, root ratings are not always reflective of yield. 4) Cost/Benefit analysis of rootworm application machinery indicated that the level of reducing corn rootworms by a given soil insecticide is influenced by many factors, and is quite complex. 5) Treatment for the control of rootworms in 1988 was economical if soil insecticides were applied at planting time. Further, scouting fields that were treated at planting was economical to establish a data base for determining the value of similiar future treatments. 6) In 1988, slot injection treatments applying 0.37 kg (AI)/ha (0.33 lb/a) were economical while injection applications at 1.12 kg (AI)/ha (1 lb/a) were not, justifying an alternative application method. 7) Application of fertilizer was not always economical, especially in 1988, a dry year that did not allow the full benefit of both soil insecticides and fertilizers to be realized. In general, slot injection at the 0.37 kg (AI)/ha (0.33 lb/a) rate with fertilizer was economical for both years at the Milan site. At the Western Branch, 1989 was the only year that this treatment was economical. 8) If granular soil insecticides are banned or severely restricted, the precedent set by such an action will be felt deeply throughout 120 U. S. corn growing regions. The future of granular soil insecticides is in doubt, either for public relations purposes or economics that would not justify future re-registrations of a corn soil insecticide whose label has been severely restricted. 9) Further research with new application technologies such as slot injection will encompass flexibility of application timing, costs, and new soil insecticide chemistry. 10) Acceptance of slot injection application machinery will occur if the following conditions are met: 1. An outright ban or restriction of a soil insecticide which is so severe that the soil insecticide is not used in the same capacity as before; 2. Further regulations restrict the small-mid sized farm operator from applying his own pesticides leaving the responsibility of such a task to a licensed applicator; 3. Incentives to practice IPM in corn or other field crops by either state or federal programs would encourage agricultural consultants to expand, driven by environmental concerns; 4. Fertilizer dealers, consultants and pesticide manufacturing companies collaborate and demonstrate the demand for slot injection application machinery to farm implement manufacturers. 121 REFERENCES Apple, J. W. , H. C. Chiang, L. M. English, L. K. French, a. J. Keaster, G. F. Krause, Z. B. Mayo, J. D. Munson, G. J. Musick, J. C. Owens, E. E. Rasmussen, R. E. Sechriest, J. J. Tollefson and J. L. Wedberg. 1977. Impact of northern and western corn rootworm larvae on field corn. N. Cent. Reg. Res. Pub. 239. Wis. Agric. Exp. Sta. Bergman, M. K. J. J. Tollefson and P. N. Hinz. 1981. Sampling scheme for estimating populations of corn rootworm larvae. Environ. Entomol. 10:986-990. Bergman, M. K., J. J. Tollefson and P. N. Hinz. 1983. Spatial dispersion of corn rootworm larvae in Iowa cornfields. Environ. Entomol. 12:1443-1446. Branson, T. F., G. R. Sutter and J. R. Fischer. 1982. Comparison of tolerant and a susceptible maize inbred under artificial Infestations of Diabrotica virgifera virgifera : yield and adult emergence. Environ. Entomol. 11:371-372. Cardwell, V. B. 1982. Fifty years of Minnesota corn production: sources of yield increase. Agron. Jour. 74:985-990. Cashman, C. M,, M. A. Martin and B. A. McCarl. 1981, Economic consequences of bans on corn (Z e a m a y s ) and soybean (G l y c i n e m a x ) herbicides commonly used on Indiana farms. Weed Sci. 29:323-228. Edwards, C. R. and F. T. Turpin. 1989. Managing corn rootworms - 1989. Purdue Cooperative Extensin Service, E-49. Foster, R. E., J. J. Tollefson, J. P. Nyrop and G. L. Hein. 1986. Value of adult corn rootworm (Coleoptera: Chrysomelidae) population estimates in pest management decision making. J. Econ. Entomol. 79:303-310. Gray, M. E. and J. J. Tollefson. 1987. Influence of tillage and western and northern corn rootworm (Coleoptera: Chrysomelidae) egg populations on larval populations and root damage. J. Econ. Entomol. 80:911-915. Hall, F. R. and J. P. Reed. 1988. Improved biotargeting of soil- applied pesticides. BCPC 39:191-204. Hills, T. M. and D. C. Peters. 1971. A method of evaluating post planting insecticide treatments for control of western corn rootworm larvae. J. Econ. Entomol. 64:764-765. 122 Horn, D. J. 1988. Ecological approach to pest management. Chap. 3: 35-61. Guilford Press, N. Y. , New York. Jordan, V. W. L. and G. R. Stinchcombe. 1988. Cost benefits of integrating nitrogen, plant growth regulators and fungicides in winter barley. Crop Prot. 7:252-257. Karr, L. L. and J. J. Tollefson. 1987. Durability of Pherocon AM trap for adult western and northern corn rootworm sampling. J. Econ. Entomol. 80:891-896. Knight, F. H. 1921. Risk, uncertainty, and profit. Boston: Houghton Mifflin Co. 312 pp. Lockertz, W. E., G. Shearer, S. Sweeney, G. Kuepper, D. Winner and D. E. Kohl. 1980. Maize yields and soil nutrient levels with and without pesticides and standard commercial fertilizers. Agron. Jour. 72:65-72. Mayo, Z. B. and L. L. Peters. 1978. Planting vs. cultivation time applications of granular soil insecticides to control larvae of corn rootworms in Nebraska. J. Econ. Entomol. 71:801-803. Metcalf, R. L. 1980. Changing role of insecticides in crop protection. Ann. Rev. Entomol. 25:219-256. Metcalf, R. L. 1986. Foreward, in: J. L. Krysan and T. A. Miller (ed.) Methods for the Study of Pest Diabrotica. Springer-Verlag, New York, NY, pp. vii-xv. Naranjo, S. E. and A. J. Sawyer. 1988. Impact of host phenology on the population dynamics and oviposition of Northern corn rootworms in field corn. Environ. Entomol. 17:508-521. Osteen, C. and F. Kruchler. 1986. Potential bans of corn and soybean pesticides: Economic implications for farms and consumers. U.S. Dep. Agric., Econ. Res. Serv. AER-546. Osteen, C. J. and L. Suguiyama. 1988. Losing chlordimeform use in cotton production. U.S. Dep. Agric., Econ. Res. Serv. AER-546. Petty, H. B., D. E. Kuhlman and R. E. Sechriest. 1969. Corn yield losses correlated with rootworm larval populations In Proceed. NCB- ESA 24:141-142. Reed, J. P., R. J. Kremer and A. J. Keaster. 1987. Characterization of microorganisms in soils exhibiting accelerated pesticide degradation. Bull. Environ. Contam. Toxicol. 39:776-782. 123 Reed, J. P., R. J. Kremer, A. J. Keaster and H. D. Kerr. 1989. Microbial degradation of some soil insecticides, herbicides and insecticide-herbicide combinations. Bull. Environ. Contam. Toxicol. 42:676-681. Ritchie, S. W. and J. J. Hanway. 1982. How a corn plant develops. Iowa Sta. Univ. Coop. Ext. Serv. SR 48. Ross, G. J. S. 1980. Maximum likelihood program refernce manual 3.06 Rothamstead Exp. Sta. Harpenden, U.K. 289 pp. Ruppel, R. F. 1984. Model for effective timing of an insecticide. J. Econ. Entomol. 77:1083-1085. SAS Institute. 1982. SAS user's guide: statistics. SAS Institute, Cary, N .C. Spike, B. P. and J. J. Tollefson. 1988. Western corn rootworm larval survival and damage potential to corn subjected to nitrogen and plant density treatments. J. Econ. Entomol. 81:1450-1455. Stamm, D. E., Z. B. Mayo, J. B. Campbell, J. F. Witkowski, L. W. Anderson and R. Kozub. 1985. Western corn rootworm (Coleoptera: Chrysomelidae) beetle counts as a means of making larval control recommendations in Nebraska. J. Econ. Entomol. 78:794-798. Stemerhof, M. 1987. The economics of herbicide use on corn and soybeans in southwestern Ontario. A Final Report for the Ontario Pesticides Advisory Committee. Ontario Ministry of the Environment, Toronto. Stemerhof, M . , C. J. Swanton, A. S. Hamill and R. H. Brown. 1988. Economics of herbicied use on corn and soybeans in Ontario. Weed Sci. 2:466-472. Stern V. M., R. F. Smith, R. van den Bosch and K. S. Hagen. 1959. The integrated control concept. Hilgardia 29:81-101. Suett, D. L. and A. R. Thompson. 1985. The development of localized insecticide placement methods in soil. Proceedings British Crop Protection Council Symposium on Application and Biology 28, 171-185. Southwood, T. R. E. 1966. Ecological methods with particular reference to the study of insect populations. First ed. Chapman and Hall, London. 391.pp. Taylor, L. R. 1961. Aggragation, variance, and the mean. Nature (London) 189:732-735. 124 Thompson, A. R . , H. R. Howse and G. W. Edmonds. 1988. Liquid insecticides and fertilizer treatments applied under seed at sowing: aspects of their porformance and relevance to systems of reduced- input, sustainable agriculture. In: Pests and Diseases. 2:845-852. Turpin, F. T. and J. M. Thieme. 1977. Impact of soil insecticide usage on corn production in Indiana: 1972-1975. J. Econ. Entomol. 71: 83-86. Turpin, F. T., L. C. Dumenil and D. C. Peters. 1972. Edaphic and agronomic characters that affect potential for rootworm damage to corn in Iowa. J. Econ. Entomol. 65:1615-1619. Wearing, C. H. 1988. Evaluating the IPM implementation process. Ann. Rev. Entomol. 33:17-38. Weiss, M. J. and Z. B. Mayo. 1983. Potential of corn rootworm (Coleoptera: Chrysomelidae) larval counts to estimate larval populations to make control decisions. J. Econ. Entomol. 76:158- 161. 125 Table 23. Chi-Square goodness fit tests of negative binomial distributiona for corn rootworm larvae populations at Bluffton, Western Branch and Milan, Ohio sites in 1988. Negative Binomial Site N X s^ df Chi-Square Value Bluffton 52 2.21 1.97 4 3.49 * Western Branch 95 2.38 2.63 4 6.20 * Milan 95 2.37 0.02 4 3 .20 * " ' * Negative binomial Chi-Square values < 9 . 4 9 indicates significance at p=0.05 level. 126 Table 24. 1989 Chi-Square goodness of fit tests of negative binomial distributions for corn rootworm larvae populations at Western Branch and Milan, Ohio sites in 1989. Negative Binomial Site N X s— df Chi-Square Value Western Branch 165 0.32 0.63 4 5.41 * Milan 150 0.34 0.62 4 4.28 * * Negative binomial Chi-Square values < 9 . 4 9 indicates significance at p=0.05 level. i Table 25. Required number of samples per hectare (acre) to attain a level of sampling accuracy for assessing corn rootworm larval populations at respective sites and years^. 1988 1989 Accuracyi Bluffton Western Branch Milan Western Branch Milan 95 400 (160) 380 (152) 450 (180) 3222 (1289) 3760 (1504) 90 100 ( 40) 95 ( 38) 113 ( 45) 805 ( 322) 940 ( 376) 80 25 ( 10) 25 ( 10) 25 ( 10) 202 ( 81) 235 ( 94) 70 10 ( 4) 10 ( 4) 10 ( 4) 90 ( 36) 105 ( 42) 60 8 ( 3) 5 ( 2) 5 ( 2) 56 ( 20) 60 ( 24) 50 5 ( 2) 5 ( 2) 5 ( 2) 33 ( 13) 38 ( 15) ^ Accuracy = 1-p. where p = level of significance. Table 26. Scouting costs ($) per hectare ($/acre) for a given level of accuracy at respective sites and years^. 1988 1989 Accuracy Bluffton Western Branch Milan Western Branch Milan 95 164.0 (65.6) 155.8 (62.3) 184.5 (73.8) 1321.0 (528.5) 1541.6 (616.00) 90 41.0 (16.4) 38.9 (15.6) 46.3 (18.5) 330.0 (132.0) 256.2 (154.20) 80 10.3 ( 4.1) 10.3 ( 4.1) 10.3 ( 4.1) 82.8 ( 33.2) 96.4 ( 38.50) 70 4.1 ( 1.6) 4.1 ( 1.6) 4.1 ( 1.6) 36.9 ( 14.8) 43.1 ( 17.20) 60 3.3 ( 1.2) 2.1 ( 0 .8) 2.1 ( 0 .8) 20.5 ( 8.2) 24.6 ( 9.84) 50 2.1 ( 0 .8) 2.1 ( 0 .8) 2.1 (0.8) 13.3 ( 5.4) 15.6 ( 6.20) 1 Based upon 0.41/plant = 5 min/plant x number of plants/acre x 1 hr/60 min x $5.00/hr. ro o o Table 27. T-values and significance levels of regressions describing the relationship of first larval counts or root ratings to predict yield in the untreated checks for respective sites for 1988. 1988 First Larval Counts First Root Rating Site Intercept Slope T-value P>T Intercept Slope T-value P>T Bluffton 80.69 -2.87 0.25 0.0039 17.84 2.28 0.38 0.7074 Western Branch 75.53 -2.37 0.17 0.0041 153.93 -35.09 1.01 0.3469 Milan 69.69 -1.48 0.44 0.6089 53.04 4.81 0.68 0.5095 ro Table 28. T-value and significance of regressions describing the relationship of first larval counts or root ratings to predict yield in the untreated checks for repective sites for 1989. 1989 First Larval Counts First Root Ratings Site Intercept Slope T-value P>T Intercept Slope T-value P>T Western Branch 136.79 -5.81 1.43 0.1806 79.40 17.09 0.93 0.6221 Milan 86.27 -6.43 1.95 0.0609 66.71 9.86 0.47 0.2425 131 Table 29. Cost/benefit ratios of various soil insecticide application treatments without fertilizer for Milan, Ohio site in 1988 and 1989. 1988 1989 Treatment Prophylactic Scouting Prophylactic Scouting Planting time 1.12 kg/ha (1 lb/a) Chlorpyrifos 0.43 0.56 0.12 0.16 Diazinon 0.24 0.31 0.17 0.22 Isazophos 0.19 0.25 0.21 0.27 0.74 kg/ha (0.66 lb/a) Injection 1.12 kg/ha (1 lb/a) Chlorpyrifos 1.41 1.97 0.39 0.54 Diazinon 1.04 1.45 0.23 0.32 Isazophos 1.09 1.52 0.21 0.29 0.74 kg/ha (0.66 lb/a) Inj ection 0.37 kg/ha (0.33 lb/a) Chlorpyrifos 0.54 0.76 0.49 0.69 Diazinon 0.53 0.74 0.17 0.24 Isazophos 0.30 0.42 0.22 0.31 132 Table 30. Cost/benefit ratios of various soil insecticide application treatments with fertilizer for Milan, Ohio site in 1988 and 1989. 1988 1989 Treatment Prophylactic Scouting Prophylactic Scouting Planting time 1.12 kg/ha (1 lb/a) + 52.6 kg N/ha (47 lb/a) Chlorpyrifos 2.05 2.87 0.25 0.33 Diazinon 1.88 2.44 4.59 5.96 Isazophos 0.16 0.22 0.22 0.29 0.74 kg/ha (0.66 lb/a) + 52.5 kg N/ha (47 lb/a) Injection 1.12 kg/ha (1 lb/a) + 52.6 kg N/ha (47 lb/a) Chlorpyrifos 1.91 2.67 0.41 0.57 Diazinon 4.14 5.38 0.21 0.29 Isazophos 0.79 1.10 0.19 0.27 0.74 kg/ha (0.66 lb/a) + 52.6 kg N/ha (47 lb/a) Inj ection 1.12 kg/ha (1 lb/a) + 52.6 kg N/ha (47 lb/a) Chlorpyrifos 0.25 0.35 1.56 2.18 Diazinon 0.78 1.01 0.27 0.38 Isazophos 0.39 0.55 0.32 0.45 133 Table 31. Cost/benefit ratios of various soil insecticide application treatments without fertilizer at the Western Branch site in 1988 and 1989. 1988 1989 Treatment Prophylactic Scouting Prophylactic Scouting Injection 1.12 kg/ha (1 lb/a) Chlorpyrifos 1.21 1.69 0.74 1.03 Diazinon 0.34 0.47 0.54 0.76 Isazophos 0.74 1.03 0.72 1.01 0.74 kg/ha (0.66 lb/a) Injection 0.37 kg/ha (0.33 lb/a) Chlorpyrifos 0.32 0.45 0.66 0.92 Diazinon 1.29 1.80 0.68 0.95 Isazophos 0.27 0.38 0.33 0.46 0.74 kg/ha (0.66 lb/a) 134 Table 32. Cost/benefit ratios of various soil insecticide application treatments with fertilizer at the Western Branch site in 1988 and 1989. 1988 1989 Treatment Prophylactic Scouting Prophylactic Scouting Injection 1.12 kg/ha (1 lb/a) + 52.6 kg N/ha (47 lb/a) Chlorpyrifos 1.06 1.48 1.15 1.61 Diazinon 2.16 3.02 1.53 2.14 Isazophos 0.46 0.64 2.20 3.08 Inj ection 0.37 kg/ha (0.33 lb/a) + 52.6 kg N/ha (47 lb/a) Chlorpyrifos 0.19 0.27 0.25 0.35 Diazinon 0.43 0.60 0.55 0.77 Isazophos 0.14 0.19 0.25 0.35 C H A P T E R V INFLUENCE OF EDAPHIC AND METEOROLOGICAL FACTORS UPON THE LATERAL AND HORIZONTAL MOVEMENT OF THREE SOIL INSECTICIDES APPLIED AT PLANTING AND BY SLOT INJECTION Introduction Walker (1971) reviewed the role of granular soil insecticides in controlling a multitude of soil borne insect pests, environmental implications of use and future directions/developments of granular insecticide research. Felsot (1986) examined and summarized the current status of pesticides under conservation tillage systems, notably soil insecticides. However, these reviews did not discuss granular soil insecticide non-target effects such as bird toxicity. Since 1985, EPA special reviews concerning toxicity of carbofuran granules to birds may lead to cancellation, but substantiation of such action is pending further study and review (Ellenberger, 1989). However, the question of avian toxicity of granular formulations does not end with carbofuran, but a,special review of three other soil insecticides, ethoprop, phorate and terbufos will begin in 1990 (Urbain, 1988). No doubt, precedent 135 136 will be set with carbofuran, perhaps with three other soil insecticides as well. The result could be a windfall of regulation concerning use of granular agricultural chemicals (Hall and Reed, 1988). Most granular soil insecticides are applied at planting to control corn rootworms. However, only a few papers have observed the effect of granular soil insecticide placement, namely banding over the row either ahead of/or behind the planter press wheel, in furrow or broadcast (Lichtenstein et al. 1973; Read, 1976; and Singh et al. 1985). In addition, birds may not be the only organisms affected by granular soil insecticides. Run-off studies by Baker and Johnson (1979) indicated rainfall was a key factor in the movement of pesticides into aquatic ecosystems. Subsequent studies investigating the influence of tillage (Abou-Assaf et al. 1986; Baker and Johnson, 1983; Baker and Johnson, 1978) found that pesticide run-off could be reduced with the proper tillage practice for a given site. Wauchope and Leonard (1980) agreed that tillage had the greatest potential to reduce run-off, however they alluded to timing of pesticide application as well as less risky methods of soil insecticide placement. This meant the application of liquid pesticides where available for use, could offer some unique incorporation/placement possibilities that granules do not possess. Application of liquid soil insecticides has been limited to spray applications to turf or vegetable insect pests (Getzin, 1985; Niemczyk and Krueger 1982 and 1987; Read, 1976; Sears et al. 1979). Indeed, studies comparing chlorpyrifos persistence when applied as an insecticidal spray or granular for soil borne pests, were performed by Getzin (1985). Liquid formulations of chlorpyrifos did not persist as long as granular formulations. Ozkan et al. (1988) observed little lateral movement of chlorpyrifos from point of injection and concluded that point injection was not practical in turfgrass. Liquid formulations of diazinon have been retained for turf and ornamental while granular formulations were lost due to geese poisoning (Anonymous, 1986). The flexibility afforded by liquid formulations of soil insecticides will probably maintain their use to control pests that were once controlled by granular formulations. However, the knowledge base on optimizing the use of these liquid formulations must increase. Although the soil insecticide market is valued at about $1 billion much of the testing in the field and laboratory is aimed at defining the technical profile of candidate pesticides. This profile, which has become part of the screening cascade is increasingly dominated by environmental attributes (Gordon et al. 1989). The objective of this study was to observe the influence of insecticide physico-chemical properties that might be responsible for the lateral and vertical movement of soil insecticides applied either as a planting time or slot injection treatment. Information gained from this study might advance application technology of soil insecticides to a point where alternative application methods, such as slot injection would be seriously considered by addressing the environmental concerns that have plagued soil applied pesticides. 138 Materials and Methods Field Studies 1987-89 In 1987, two field sites were chosen to conduct the study. These sites were at the Ohio Agricultural Research and Development Center near Wooster, Ohio in a field where half was in conventional tillage and the other half in no-tillage. The site had corn grown for five previous years. The other site utilized in 1987 was located near Bluffton, Ohio on a private farm. In 1988, two other sites were added to the Wooster and Bluffton sites. The third site was located at the Western Branch near South Charleston, Ohio and the last site studied in 1988 was located at Milan, Ohio. In 1989, all sites were utilized except the Bluffton site, because planting was delayed beyond 1 June, 1989. Further, the sites chosen represent a different soil type, each of which are indicative of the corn producing regions of Northern, Central and Western Ohio (Figure 4). A randomized complete block design was replicated four times in 1987 and 1988 at all sites except Western Branch which had three replicates. In 1989, the Wooster and Western Branch sites used three replicates while the four replicate study remained unchanged at the Milan site. Soil insecticides were applied at the rate of 1.12 kg (AI)/ha (1 lb/acre) for both planting and slot injection treatments. Another 107 treatment rate was 0.37 kg (AI)/ha (0.33 lb/acre) of slot injection. Isazophos was not applied at 1.12 kg (AI)/ha (1 lb/a) instead it was applied at 0.74 kg (AI)/ha (0.66 lb/a) for planting time and slot injection treatments. Since row spacing was 76 cm wide (30 in) and length was 13 m, planting treatments of granular soil insecticides required the use of granular mixing boxes. Gandy granule application units applied soil insecticide granules ahead of the press wheel in 10 cm (7 in) bands at the Wooster and Bluffton sites. The Western Branch and Milan sites had planting time applications made with a John Deere Maxi-Merge 7000 planter operating at 6.4 km/hr (4 mph). Planting time and injection dates are listed for all sites and years in Table 39. Slot injection treatments were made with slot injection apparatus (Figure 1). Separate spring loaded arms were mounted to a 5 x 10 cm (2 x 4 in) tool bar centered over the row with 25.4 cm (10 in) spacing. The swing bars had independently mounted fluted coulters, on which a 0.00025 mm (0.0001 in) diameter solid stream nozzle was mounted about 4 cm (1.75 in) above soil and 2.0 cm (0.75 in) behind the coulter (Model 12935, Yetter Manufacturing, Colchester, IL 62326). The pump (Model 311, Cat Pumps, Inc., P. 0. Box 885, Minneapolis, MN 55440) was a stainless steel, high pressure triplex pump which operated at 3450 kPa (500 psi) while travelling at a ground speed of 4.8 km/h (3 mph) producing a volume of 73.8 L/ha (20 gpa). The pump was driven by a hydraulic motor. Three soil insecticides were chosen for this study on the basis of low mammalian toxicities, available as both a granular and liquid formulation and an array of water solubilities and vapor pressures (Table 40). These three soil insecticides were: chlorpyrifos (0,0- Diethyl 0-3, 5, 6-trichloro-2-pyridyl phosphorothioate) formulated as a 15G and 4E sold under the trade name Lorsban by Dow Chemical U.S.A. (P.O. Box 1706, Midland, MI 53280); diazinon (0,0-Diethyl 0-(2-isopropyl-6-methyl-4-pyrimidinyl) formulated as a 14G and 4E. and sold under the trade name Diazinon by Ciba-Geigy (P. 0. Box 18300 Greensboro, NC 27419); and isazophos (0,0-Diethyl 0-(5-chloro-l-(methyl)-lH-l,2,4 triazo-3-yl) formulated as a 10G and 4E and sold under the trade name of Brace by Ciba-Geigy (P. 0. Box 18300 Greensboro, NC 27419). Soil sampling in the middle of the row for residue analysis of planting time applications consisted of A = 0-2"; B = 2-4", C = 4-6"; and D = 18" vertically in the soil profile, a 3.75 cm diameter (1.5 in) soil probe was used to extract soil core samples (Figure 30). Slot injection treatments required a different sampling scheme, where the first soil sample, A was approximately 3.75 cm (1.5 in) below the soil surface next to the injection slot. Probing another 5.00 cm (2 in) resulted in acquiring soil sample C. Then, the next to this probing, perpendicular to the injection slot samples B and D were obtained in the same manner as samples A and C (Figure 31). In 1987, only the A and B samples were obtained at the Wooster and Bluffton sites; during 1988-89, A, B, C, D, and E samples were taken at all sites studied during those years (Figure 43). A 45 cm deep soil sample was also obtained to assess any possible groundwater contamination. This deep sample was obtained by using a post-hole digging attachment for a tractor or by manual post hole digging. After holes were dug, they were covered with a 900 cm square piece of plywood and soil was packed around the cover to shed precipitation. To prevent contamination, all soil tools were wiped clean with a piece of cloth and scoured thoroughly in an untreated plot. In the deep samples, contamination was prevented by re-digging the bottom of the hole, then removing a 10 cm wide by 2.5 cm deep core, then concentrically sampling within this newly dug hole with a smaller diameter sampler. Date of sampling was as follows: 1 = at application; 2 = 7 days later; 3— 14 days; 4 = 30 days; and 5 = 45 days. Soil samples were stored in Ziploc bags and frozen until analyzed. Dates of sampling differed for the specific application methods, therefore environmental conditions are different for each application method (Tables 41 and 42). Laboratory Analyses Extraction of pesticide residues started with a 50 g aliquot that was shaken in 100 ml of acetone-hexane (1:0 mixture) for 30 minutes. The resulting mixture was filtered through glass filter paper and washed twice with 15 ml portions of hexane. The sample was poured into a 142 separatory funnel and rinsed in a Buchner funnel in which two 50 ml portions of dichloromethane were added. Ten ml of a saturated NaCl solution was added to the separatory funnel and the bottom layer was saved; solvent layer was filtered through Na2S0^ and the water layer was partitioned by two 25 ml portions of dichloromethane. The solvent was drained off through Na2SQ^ and evaporated to dryness on a flash evaporator. Samples were eluted to 10 ml and analyzed by GLC. A Varian Gas chromatograph was equipped with an flame ionization detector using the N detector. An DC-200 column was employed in which column temperature was (215°C). All data was statistically analyzed using analysis of variance procedures at p = 0.05 level of significance. The experimental design at the Wooster site was a split-split-split plot design (Cochran and Cox, 1957). Main plots were insecticide, split plots were tillage, split-split plots were sampling method and split-split-split plots were date of sampling. All data was sorted according to site and application method since both site and sampling methods were different. The other sites in this study were analyzed as split-split plot designs (Cochran and Cox, 1957). Main plots were insecticides, split plots were sampling method and split-split plots were date. The least significant difference was used to separate means only when the comparison wise F-values were significant at the p - 0.05 level. 143 RESULTS AND DISCUSSION Field Studies 1987-89 In 1987, the objective of this study was to observe lateral movement of slot injection treatments and to identify any problems that might be encountered with sampling. In Table 33, movement and dissipation was observed between samples A and B at the Bluffton site. Note no comparison could be made between tillage at this site. However, in Table 34 at the Wooster site, residues of slot injected soil insecticides did not persist as long as correspondingly similar treatments in conventional tillage. This was encouraging, indicating that rootworm control was adequate on the basis of insecticide movement and concentration in the root zone. Sutter (1982) determined LDcjq for rootworm larvae, and found chlorpyrifos concentrations in this study exceeded the bioassay LD5Q value (0.62 ppm) of Sutter (1982). Indeed, Suett (1988) identified the establishment of such protocol as a priority if alternative application technology of soil pesticides was to advance any further. The variable, sampling method x insecticide, was highly significant (Tables 35-36). This indicated that movement in planting time and the two slot injection treatments was different for an insecticide at a given site under the specific sampling methods for the two year duration of the study. In general, no soil insecticides were detected at 45 cm (18 in.) and therefore none of the insecticides applied by the application methods in this study posed a ground water contamination threat (Figures 5-29). Indeed, these observations only lend credence to the conservative nature of the GUS model, which is used to predict the leaching potential through a soil profile for a specific pesticide, tending to error on the side of caution (Gustafson, 1989). According to Table 41, 1988 was a record dry year. The drought persisted for up to 5 months at the Bluffton site while the Western Branch site was largely unaffected although rainfall was down from the norm. In Table 42, an extremely wet growing season resulted in the ommission of the Bluffton site in 1989. Therefore the use of this information would not be representative of what would occur in a normal year. Further, the difficulty of explaining what was occurring in normal years is certainly not accurate. Therefore, no attempt was made to model the behavior or fate, however the movement of each insecticide under the specified conditions was observed with keen interest. Abstractly, recall that 1988 was a dry year while 1989 was extremely wet. In addition, planting time application residues in the A samples were always greater than any other sampling method. In Figure 5, during 1988 at Wooster, chlorpyrifos demonstrated greater horizontal movement under conventional tillage conditions while isazophos (Figure 6) moved further down the soil profile in the no-tillage treatments. However, little change in vertical and less so for horizontal movement occurred in 1989 between tillages for chlorpyrifos (Figures 7 and 8). On the other hand, isazophos vertically moved more in 1989 than 1988 in conventional tillage treatments (Figures 5 and 7) and significantly greater than the no-till treatments (Figures 6-8). Diazinon behaved in a similiar fashion as isazophos in both years (Figures 5 and 7) with respect to tillage. However, greater vertical mobility of diazinon residues occurred in 1989 than 1988 regardless of tillage (Figures 5 and 7 ; 6 and 8) . Planting time treatments at the Bluffton site displayed no vertical movement, though detectable residues of isazophos were greater than any other insecticide (Figure 9). At the Milan site, diazinon residues demonstrated greater mobility in 1988 than 1989 (Figure 10). In 1988 at the Wooster conventional tillage site, diazinon residues in the 1.12 kg (AI)/ha (1 lb/a) injection treatments moved laterally more than vertically (Figure 12). Isazophos behaved the same, except the lateral distribution was greater in diazinon treated plots while chlorpyrifos moved little, if at all. Only chlorpyrifos and isazophos residues were observed in the D samples. In no-till plots, few differences were observed among the insecticides in the A and B samples while chlorpyrifos had significantly greater residues in the C sample (Figure 13). Further, movement in the D sample was similiar to conventional tillage treatments indicating similarity between the two tillage profiles at this depth. 146 Residues in 1989 at the Wooster site in conventional tillage vividly demonstrated the influence of moisture on a very water soluble soil insecticide (Table 14). Note, isazophos residues did not display the typical dissipation curve where initial concentrations are the highest of all samples. Both chlorpyrifos and diazinon residues were significantly less than isazophos at the B, C, and D samples. Chlorpyrifos and diazinon are not as water soluble as isazophos, hence under the wetter conditions in the soil profile of 1989 isazophos diffused. In no-tillage residue movements, both lateral and vertical movements were significantly greater in the chlorpyrifos, isazophos treatments, while the diazinon treatments at this site dissipated faster than either isazophos or chlorpyrifos (Figure 15). The Bluffton and Western Branch sites specific soil types were identical (Typic Argiaquoll), although their respective soil series were not (Blount-Pewamo transition; Brookston-Cosby). Dissipation of isazophos was more rapid than any other soil insecticide at the Bluffton site (Figure 16). On the otherhand, diazinon dissipated, diffused laterally while isazophos and chlorpyrifos did not behave the same as diazinon. In general, during 1988 at the Western Branch site, the 1.12 kg (AI)/ha (1 lb/a) injected isazophos residue diffusions were significantly greater than either chlorpyrifos or diazinon (Figure 17). However, in 1989 vertical movement was the rule rather than the exception. The order of magnitude of diffusion shows the greatest vertical displacement with the more water soluble compound, isazophos followed by chlorpyrifos then diazinon (Figure 18). 147 Since the Milan site was a sandy soil, leaching throughout the soil profile would be expected. In 1988, greater vertical movement was observed for all compounds while small increments of lateral movement occurred (Figure 19). However, under wet conditions as in 1989, chlorpyrifos had a tendency to move vertically more so than any other soil insecticide. This is not surprising, since the soil type at this site was a sandy loam, Diazinon appeared to be rapidly metabolized, while isazophos moved laterally and to a lesser extent vertically (Figure 20). In 1988 at the Wooster site, the 0.37 kg (AI)/ha (0.33 lb/a) chlorpyrifos and isazophos residues moved equal increments both laterally and vertically throughout the soil profile in the conventional tillage plots (Figure 21). However, the diazinon residues in the no-till plots at Wooster site demonstrated the greatest movement of any insecticide (Figure 22). Chlorpyrifos moved laterally, however isazophos moved both horizontally and to a lesser extent, vertically through the no-till profile. Vertical and horizontal diplacement of 0.37 kg (AI)/ha (0.33 lb/a) residues was prevalent in conventional tillage treatments at the Wooster site in 1989 (Figure 23). Chlorpyrifos showed more mass movement than either isazophos or diazinon. In no-till plots at the Wooster site during 1989, isazophos residues in the A sample were significantly less than chlorpyrifos and diazinon residues (Figure 24). However, in the B sampling zone diazinon showed more movement than the other insecticides. Only isazophos residues were detected in the D sample zone. 1 48 In 1988 at the Bluffton site, vertical movement was significantly greater for all insecticides applied at 0.37 kg (AI)/ha (0.33 lb/a) than horizontal movement to the B sample. Indeed, residues were detected in the D sample (Figure 25). At the Western Branch in 1988, the 0.37 kg (AI)/ha (0.33 lb/a) movement was variable among all three soil insecticides (Figure 26). Chlorpyrifos showed the greatest movement of any soil insecticide, detection even at the D sample zone. Residues indicating movement of diazinon and isazophos were not significantly different in the B and C zones. A striking similarity among diazinon and chlorpyrifos residues, with the exception of movement into the D zone by chlorpyrifos was observed in 1989 (Figure 27). Isazophos residues were detected in the D zone in 1989, unlike 1988 (Figures 27 and 26). In 1988, residue analysis at the Milan site in 1988 for movement of 0.37 kg (AI)/ha (0.33 lb/a) applications are shown in Figure 28. Vertical movement occurred to a greater extent, all insecticides were detected in C and D zone samples (Figure 28). However, isazophos showed the greatest displacement of any soil insecticide. In 1989, diazinon demonstrated the greatest movement of any soil insecticide, while chlorpyrifos residues in the B through D samples were barely detectable (Figure 29). Despite the wet soil conditions, isazophos applied at the rate of 0.37 kg (AI)/ha (0.33 lb/a) did not move appreciably. Movement of soil insecticides through a soil profile is a complex process. Several hazard assessment models are available, which require the use of one or several variables that are properties of the soil insecticide (Briggs, 1981; Kenaga and Goring, 1980). However, one noteworthy estimator is the GUS model which our study confirmed as an appropriate estimator of soil insecticide movement (Gustafson, 1989). The GUS value and nomogram is extremely conservative and errors on the side of caution that a soil insecticide/pesticide would be an effective leacher. Despite the observed differences between years and tillages at the Wooster site, the GUS model remained a truly conservative measure of leaching potential. In addition to the environmental information on soil insecticide movement, we observed concentrations in the planting time application treatments were not always capable of attaining mortality of rootworm larvae (Sutter, 1982). Hibbard and Bjostad (1989) demonstrated that some of the activity of a soil insecticide may attributed to a repellency effect. Indeed, we feel this may be a artifact of planting time applications while slot injection applications would produce concentrations throughout the soil profile which would elicit significantly more mortality than planting time applications. Further, the repellency effect of planting time applications may explain why resistance has not developed in the planting time application scenarios, yet high adult beetle counts and low root ratings prevail. This situation has perplexed both field and laboratory researchers, however the data base on lateral movement of soil insecticides is nominal and this study has demonstrated that even under dry conditions in a sandy soil, leaching still occurs. On the other hand, soil insecticides in saturated clay soils moved laterally just as much as they moved vertically through the soil profile at concentrations which would result in mortality of rootworm larvae. The high organic matter content of reduced/conservation tillage programs may reduce the availabilty of soil insecticides throughout the soil profile due to lower pH of significantly greater quantities of organic acids (Felsot, 1987) and higher bulk densities resulting in significantly greater number of microsites (Blevins et al. 1983). However, in 1989 more vertical movement of isazophos occurred in no-till plots than any other soil insecticide. Debate over the work and implications of Hibbard and Bjostad (1989) on targeting soil insecticides with semio-chemicals against the corn rootworm complex has questioned the delivery process of planting time applications of soil insecticides. The obstacle of longevity in the semio-chemical arena may be overcome by encapsulation. However the only delivery system seen being capable of delivering semio-chemicals is the slot injector developed at the Laboratory for Pest Control Application Technology at the Ohio Agricultural Research and Development Center of The Ohio State University. Summary 1) Vertical movement in both 1988 and 1989 occurred in both tillages where a granular soil insecticide had been applied at planting time at the Wooster site. 2) At the Bluffton site, vertical movement of planting time treatments was severely restricted in 1988, unfortunately this site was not planted in 1989 due to an unusually wet spring. 3) Planting time treatments at the Milan site in 1988 demonstrated some vertical movement. However, in 1989 diazinon did not move as appreciably as in 1989. 4) In general, no soil insecticide residues were detected in the 45 cm (18 in) deep samples for 1988 or 1989 indicating that the potential for groundwater contamination by the two application methods, granules applied at planting or slot injection at the specified rates in this study is practically non-existent. 5) Regardless of application rate, slot injection treatments at the Western Branch and Milan site during both years displayed greater vertical movement. 6) Vertical movement of slot injection treatments at the Wooster no-till site was restricted, while conventional tillage treatments displayed greater vertical mobility. Lateral movement was significantly greater in the 1.12 kg (AI)/ha (1 lb/a) than the 0.37 kg (AI)/ha (0.33 lb/a) application rate. 7) Under dry conditions, diazinon moved further under dry conditions than a wet year. In contrast, isazophos mobility was enhanced under under wet conditions. Chlorpyrifos movement was greater from the initial site of application but residues did not move appreciably far at all. 8) Rate of application had little influence on slot injection application movement. The consolation concerns the mass movement of the soil insecticide at a lower rate, thus making any possibility of groundwater contamination practically impossible. 9) The quantity of soil insecticide from slot injection that moves laterally is more than sufficient to cause mortality to rootworm larvae. Where concentrations are not adequate to elicit mortality repellency may occur which might subsequently result in mortality. 153 REFERENCES Abou-Assaf, N., J. R. Coats, M. E. Gray and J. J. Tollefson. 1986. Degradation of isazophos in corn fields with conservation tillage practices. J. Environ. Sci. Health B21(6):425-446. Anonymous. 1986. Hearing before FIFRA Scientific Advisory Panel on the cancellation of diazinon for use on golf courses and sod farms. USEPA, Wash. D. C. Anonymous. 1984. Conservation tillage needs little extra herbicide. Agrichemical Age 28:28. Baker, J. L. and H. P. Johnson. 1979. The effect of tillage systems on pesticides in runoff from small water sheds. Trans. ASAE 22:554- 559. Baker, J. L. and H. P. Johnson. 1983. Evaluating the effectiveness of BMPs from field studies, pp. 281-304. In F. W. Schaller and G. W. Bailey [eds.], Agricultural management and water quality. Iowa Sta. Univ. Press. Baker, J. L., J. M. Laflen and H. P. Johnson. 1978. Effect of tillage systems on runoff losses of pesticides, a rainfall simulation study. Trans. ASAE 21:886-892. Blevins, R. L., G. W. Thomas, M. S. Smith, W. W. Frye and P. L. Cornelius. 1983. Changes in soil properties after 10 years continuous non-tilled and conventionally tilled corn. Soil and Till. Res. 3:135-146. Briggs, G. G. 1981. Theoretical and experimental relationships between soil adsorption, octanol-water partition coefficients, water solubilities, bioconcentration factors, and the PCB's. J. Agric. Food Ghem. 29:1050-1059. Ellenberger, J. 1989. Carbofuran: Special review technical support document. EPA Pos. Doc. 2/3. Felsot, A. S. 1987. Fate and interactions of pesticides in conservation tillage systems. In Arthropods in conservation tillage systems. Misc. Pub. Entomol. Soc. Amer. 65:1-52. Felsot, A. S., W. N. Bruce and K. S. Steffey. 1987. Degradation of terbufos soil insecticide in corn fields under conservation tillage practices. Bull. Environ. Contam. Toxicol. 38:369-376. Getzin, L. W. 1985. Factors influencing the persistence and ' 54 effectiveness of chlorpyrifos in soil. J. Econ. Entomol. 78:412-418. Gordon, R. F. S., K. T. Atcock and A. R. Jutsum. 1989. Soil-applied insecticides: Comparability of performance between laboratory and field. Aspect. Appl. Biol. 21:107-117. Gustafson, D.I. 1989. Groundwater Ubiquity Score: A simple method for for assessing pesticide leachibility. Arch. Environ. Toxicol. Chem. 8:339-357. Hibbard, B. E. and L. B. Bjostad. 1989. Corn semio-chemicals in insecticide efficacy and insecticide repellency toward western corn rootworm larvae. J. Econ. Entomol. 82:773-781. Kenaga, E. E. and C. A. I. Goring. 1980. Relationships between water solubility, soil adsorption, octanol-water partitioning, and concentration of chemicals in biota. ASTM Special Publ. 707: 78-115. Kuhr, R. J. and H. Tashiro. 1978. Distribution and persistence of chlorpyrifos and diazinon applied to turf. Bull. Environ. Contam. Toxicol. 20:652-656. Lichtenstein, E. P., T. W. Fuhreman, K. R. Schulz and T. T. Liang. 1973. Effect of field application methods on the persistence and metabolism of phorate in soil and its translocation into crops. J. Econ. Entomol. 66:863-866. Niemczyk, H. D. and H. R. Krueger. 1982. Binding of insecticides on turfgrass thatch, pp. 61-63. In Advances in Turfgrass Entomology. H. D. Niemczyk and B. G. Joyner [eds.] Chemlawn Corp. Worthington, OH. Niemczyk, H. D. and H. R. Krueger. 1987. Persistence and mobility of isazophos in turfgrass thatch and soil. J. Econ. Entomol. 80:950-952. Ozkan, H. E., D. L. Reichard, H. D. Niemczyk, M. G. Klein and H. R. Krueger. 1989. Subsurface point injector applicator for turfgrass insecticides. Trans. ASAE. (IN PRESS). Read, D. C. 1976. Comparison of residual toxicity of 24 registered or candidate pesticides applied to field microplots of soil by different methods. J. Econ. Entomol. 69:429-437. Sears, M. K. and R. A. Chapman. 1979. Persistence and movement of four insecticides applied to turfgrass. J. Econ. Entomol. 72:272-274. Singh, G. , Z. Singh and T. S. Kathpal. 1984. Method of application affecting phorate persistence in soil and its translocation into cotton plants. Indian J. Ent. 46:183-186. Stinner, B. R., H. R. Krueger and D. A. McCartney. 1986. Insecticide and tillage effects on pest and non-pest arthropods in corn agroecosystems. Agric. Ecosys. Environ. 15:11-21. Strnad, S. P. and M. K. Bergman. 1987. Movement of first-instar western corn rootworms in soil. J. Econ. Entomol. 16:975-978. Suett, D. L. 1988. Application to seeds and soil: recent developments, future prospects and potential limitations. In: Pests and Diseases. 2:823-832. Sutter, G. R. 1982. Comparative toxicity of insecticides for corn rootworm larvae in a soil bioassay. J. Econ. Entomol. 75:489-491. Swann, R. L. and A. Eschenroeder. 1983. Fate of chemicals in the environment. ACS Symp. Ser. 225. Amer. Chem. Soc., 320 pp. Urbain, C. D. 1989. EPA may ban Furadan. ' Farm Journal 3:29. Walker, P. T. 1971. The use of granular pesticides from the point of view of residues. Res. Rev. 40:64-132, Wauchope, R. D. 1978. The pesticide content of surface water draining from agricultural fields - a review. J. Environ. Qual. 7:459-472. Wauchope, R. D. and R. A. Leonard. 1980. Maximum pesticide concentrations in agricultural runoff: a semi-empirical prediction formula. J. Environ. Qual. 9:665-672. tillage. in site Wooster the at method sampling X Insecticide 5. Figure 1988 PPM , 1.12 kg (AI)/ha (l lb/a) planting application inconventional application (l planting lb/a) (AI)/ha kg 1.12 B D C B A SAMPLING METHOD S 0H0 ■■■ CLRYIO MUMS DIAZINON S M U M CHLORPYRIFOS ■ ■ ■ 08 Z0PH ISA 00) 0.12 (0.05) = D S L iue . netcd apigmto tteWotrst in site Wooster the at method sampling x Insecticide 6. Figure 1988, 1.12 kg (AI)/ha (1 lb/a) planting application in no-till. in application planting (1 lb/a) (AI)/ha kg 1.12 1988, PPM B D C B A SAMPLING METHOD SZP0 CLRYI0 IHHM DIAZINON IHHIHHM CHL0RPYRIF08 ISAZ0PH08 005 = 0.12 (0.0 = D 5> S L tillage. iue . netcd apigmto tteWotrst in site Wooster the at method sampling x Insecticide 7. Figure 1989, 1.12 kg (AI)/ha (1 lb/a) planting application in conventional in application planting lb/a) (1 (AI)/ha kg 1.12 1989, PPM B D C B A SSfi ISAZOPH08 ESSS&feil SAMPLING METHOD CHL0RPYRIF08 CHL0RPYRIF08 00) 0.07 = (0.05) D S L 8 1 H i i ) » i i l DIAZINON iue8 Isciiexsmln ehda h ose ie in site Wooster the at method sampling x Insecticide 8. Figure 1989, 1.12 kg (AI)/ha (1 lb/a) planting application in No-Till. in application planting (1 lb/a) (AI)/ha kg 1.12 1989, PPM ■aSfs-Ssff m m m m m m m w & m m m m m m SAMPLING METHOD ISAZOPHOS C B HOPRFS DIAZINON CHLORPYRIFOS S 00) 0.07 (0.05) = LSD 45 cm (18") cm 45 Figure 9. Insecticide x sampling method at the Bluffton site Bluffton the at method sampling x Insecticide 9. Figure 1988, 1.12 kg (AI)/ha (1 lb/a) planting time application. time planting (1 lb/a) (AI)/ha kg 1.12 1988, PPM c&&d S 0 8 H0PRF8 DIAZINON CHL0RPYRIF08 08 H Z0P ISA fci&i&Sd SAMPLING METHOD C B 00) 0.02 = (0.05) D S L 45 cm (18“) cm 45 B D t&SftSSa ISAZOPHOS CHL0RPYRIF08 h i& IB a DIAZINON LSD (0.05) = 0.22 45 cm (18") 2 Q. CL 7 l B C D SAMPLING METHOD Figure 10. Insecticide x sampling method at the Milan site in 1988, 1.12 kg (AI)/ha (1 lb/a) planting time application. i& M & il I8AZOPHO8 CHL0RPYRIF08 DIAZINON L S D (0.05) = 0.08 45 cm (18") 'ii- - 2 0. O. AV\ ^ V V < f ' <>."> m m wSSSsgsssspss? m m s m m s s B C SAMPLING METHOD Figure 11. Insecticide x sampling method at the Milan site in 1989, 1.12 kg (AI)/ha (1 lb/a) planting time application. tei&Saia ISAZOPHOS ■ ■ ■ CHL0RPYRIF08 DIAZINON LSD (0.05) - 0.16 A B C D 45 cm (18") 5 Q. £L EEtEtEttEEEsiEI z BCD SAMPLING METHOD Figure 12. Insecticide x sampling method at the Wooster site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application in conventional tillage. iue 3 Isciiexsmln ehda h ose ie in site Wooster the at method sampling x Insecticide 13. Figure 1988, 1.12 kg (AI)/ha (1 lb/a) injection application in no-till. in application injection (1 lb/a) (AI)/ha kg 1.12 1988, PPM D C B SAMPLING METHOD S 0H08 Z0PH ISA H0PRF8 DIAZINON W M o t CHL0RPYRIF08 LSD LSD (0.05) 5 m (18") cm 45 0.16 = EffSiftiftlj ISAZOPHOS CHL0RPYRIF08 KSSS3 DIAZINON LSD (0.05) = 0.06 A B CD 45 cm (18") J 0. Q. BCD SAMPLING METHOD Figure 14. Insecticide x sampling method at the Wooster site in 1989, 1.12 kg (AI)/ha (1 lb/a) injection application in conventional tillage. iue 5 Isciiexsmln ehda h ose ie in site Wooster the at method sampling x Insecticide 15. Figure 1989, 1.12 kg (AI)/ha (l lb/a) injection application in no-till. in application injection (l lb/a) (AI)/ha kg 1.12 1989, PPM D C B SAMPLING METHOD % S 0H0 ■■■ CLRYIO DIAZINON CHLORPYRIFOS ■ ■ ■ 03 Z0PH ISA ,i $;I* * m m m »*• 00) 6 0 . 0 = (0.05) D S L 5 (18") m c 45 Figure 16. Insecticide x sampling method at the Bluffton site Bluffton the at method sampling x Insecticide 16. Figure 1988, 1.12 kg (AI)/ha (1 lb/a) injection application. injection (1 lb/a) (AI)/ha kg 1.12 1988, PPM E D O B A S&S ISAZOPHOS ESS&SSj SAMPLING METHOD HOPRFS iHiU DIAZINON BiiHiidUl CHLORPYRIFOS 00) 9 0 . 0 = (0.05) D S L ISAZOPHOS CHLORPYRIFOS BSSSSS DIAZINON L S D (0.05) = 0.11 A B C D 45 c m (18") J S CL OL 7 BCD SAMPLING METHOD Figure 17. Insecticide x sampling method at the Western Branch site in 1988, 1.12 kg (AI)/ha (1 lb/a) injection application. K&S&ftil 1SAZOPHOS ■ ■ ■ CHLORPYRIFOS E S S ® DIAZINON LSD (0.05) = 0.10 A B C D 45 cm (18") im J 2 Q. m m m m O. SSSiSsss W M M t 7 / M B SAMPLING METHOD Figure 18. Insecticide x sampling method at the Western Branch site in 1989, 1.12 kg (AI)/ha (1 lb/a) injection application. Figure 19. Insecticide x sampling method at the Milan site Milan the at method sampling x Insecticide 19. Figure n 98 11 k (I/a 1 ba ijcin application. injection (1 lb/a) (AI)/ha kg 1.12 1988, in PPM S v S I j S S x v i S &&&) ISAZOPHOS t&i&l&S) D C B SAMPLING METHOD jHly HOPRFS DIAZINON CHLORPYRIFOS 00) 0.08 = (0.05) D S L 5 m (18") cm 45 D C A B Figure 20. Insecticide x sampling method at the Milan site Milan the at method sampling x Insecticide 20. Figure in 1989, 1.12 kg (AI)/ha (1 lb/a) injection application. injection (1 lb/a) (AI)/ha kg 1.12 1989, in PPM / lilM lilll y SSSi S 0H08 Z0PH ISA ESSSSS-i Wvx: x: : : : : : : :vx D C B SAMPLING METHOD H0PRF8 SS DIAZINON S lS f f E CHL0RPYRIF08 00) 0.04 = (0.05) D S L 5 (18") m c 45 D C A B j ovninl tillage. conventional Figure 21. Insecticide x sampling method at the Wooster site Wooster the at method sampling x Insecticide 21. Figure n 98 03 k (I/a 03 l/) neto plcto in application injection lb/a) (0.33 (AI)/ha kg 0.37 1988, in PPM &Sa ISAZOPHOS k&SS&a D C B SAMPLING METHOD H0PRF3 DIAZINON CHL0RPYRIF03 LSD LSD 00) 0.07 = (0.05) 5 (18") m c 45 D C A B J I3AZOPHOS CHLORPYRIFOS faHHttiUI DIAZINON LSD (0.05) = 0.07 A B 1.00 C D 0.80 45 c m (18") 0.70 I 0.60 s o. 0.50 a 0.40 0.30 0.20 illF^ 0.10 A B C D SAMPLING METHOD Figure 22. Insecticide x sampling method at the Wooster site in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application in no-till. ovninl tillage. conventional Figure 23. Insecticide x sampling method at the Wooster site Wooster the at method sampling x Insecticide 23. Figure n 99 03 k (I/a 03 l/) neto plcto in application injection lb/a) (0.33 (AI)/ha kg 0.37 1989, in PPM B D E D C B A ffi& IAZP 08 Z0PH ISA BfeffiS&a SAMPLING METHOD H0PRF8 DIAZINON CHL0RPYRIF08 LSD LSD 00) 0.04 = (0.05) 5 (18") m c 45 C A D B ISAZOPHOS CHLORPYRIFOS S S S iS S DIAZINON LSD (0.05) = 0.04 1.00 0.90 0.80 4 5 c m (18") 0.70 I 0.60 2 Ql0.50 Q. :*:*x*:¥:V£k 0.40 0.30 0.20 1 1 1KtSSSA 1 0.00 BCD SAMPLING METHOD Figure 24. Insecticide x sampling method at the Wooster site in 1989, 0.37 kg (AI)/ha (0.33 lb/a) injection application in no-till. Figure 25. Insecticide x sampling method at the Bluffton site Bluffton the at method sampling x Insecticide 25. Figure in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application. injection lb/a) (0.33 (AI)/ha kg 0.37 1988, in PPM 0.80 0.9 0.60 0.70 1.00 0.40 0.50 0.10 0.20 0.30 0.00 0 B D C B A &tx IAZ0H08 0PH Z I3A K&ttSxa SAMPLING METHOD HOPRFS DIAZINON CHLORPYRIFOS 00) = (0.05) D S L 5 (18 ) m c 45 0.10 site in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application. Branch injection Western lb/a) (0.33the at (AI)/ha method kg sampling 0.37 x 1988, in Insecticide site 26. Figure PPM 0.80 0.90 0.50 0.60 0.70 0.00 0.10 0.20 0.30 0.40 1.00 ■HI D C B SAMPLING METHOD 3 P 08 0PH Z I3A HOPRFS flfli DIAZINON tffljffltiS CHLORPYRIFOS LSD LSD 00) 0.08 = (0.05) 5 m (18") cm 45 D C A B j site in 1989, 0.37 kg (Al)/ha (0.33 lb/a) injection application. Branch injection lb/a)Western (0.33 the at (Al)/ha method kg sampling 0.37 x 1989, in Insecticide site 27. Figure PPM 0.90 0 0.70 0.80 1.00 0.40 0.50 0.00 0.10 0.20 0.30 . 0 6 - m m D C B SAMPLING METHOD 3 PH08 H 0P Z I3A HOPRFS DIAZINON CHLORPYRIFOS LSD 5 m (18") cm 45 00) 0.04 = (0.05) D C A B j Figure 28. Insecticide x sampling method at the Milan site Milan the at method sampling x Insecticide 28. Figure in 1988, 0.37 kg (AI)/ha (0.33 lb/a) injection application. injection lb/a) (0.33 (AI)/ha kg 0.37 1988, in PPM 0.90 0.70 0.80 0.40 0.50 0.60 0.00 0.10 0.20 0.30 D C B SAMPLING METHOD ISAZOPH08 H0PRF8 efBff DIAZINON tefflBffifl CHL0RPYRIF08 LSD LSD 00) 0.08 = (0.05) 5 m (18") cm 45 I iue 9 Isciiexsmln ehda h ia site Milan the at method sampling x Insecticide 29. Figure in 1989, 0.37 kg (AI)/ha (0.33 lb/a) injection application. injection lb/a) (0.33 (AI)/ha kg 0.37 1989, in PPM &Sil ISAZOPHOS K&iS&ifl D C B SAMPLING METHOD HOPRFS UllIl DIAZINON SUflflJISl CHLORPYRIFOS LSD 00) .04 0 = (0.05) 5 m (18") cm 45 D C A B j Surface A 0-2" B 2-4" C 4-6" Sample D is 18” from the surface Figure 30. Soil sampling scheme for planting time treatments. 1.5 " Deep Slot A B Each sample Is approximatpl y R cu Inches. C D Sample E Is loralpil 18 Inches down from the soil surface, hole dug by post hole digger. NOT TO SCALE Figure 31. Soil sampling scheme for slot injection treatments. CO PO PLEASE NOTE: Duplicate page number(s); text follows. Filmed as received. 152-182 UMI C H A P T E R V I SUMMARY AND CONCLUSIONS Introduction Current application technology for soil applied insecticides has not kept pace with recent advances in pesticide chemistry. Both eco nomic and environmental concerns as well as health of users are forc ing industry and government to look at the alternatives in pesticide application technology. Application of liquid pesticides has generally relied upon incor poration of the pesticide in the soil. Unfortunately, this scenario does not encompass preemgence applications. Therefore, a conceptuali zation of spray atomization is required to understand foliar deposi tion of pesticide sprays on an undisturbed soil surface. Granular banding and in-furrow treatments are among the oldest examples of soil insecticide methods that stress targeting. Since granular soil insecticides are used under a variety of conditions, the 152 153 understanding of dose acquisition at planting time application against pests which attack corn in early stages of development was undertaken. The implications of this information upon the screening cascade of soil insecticides will undoubtedly elucidate new parameters for the screening process. Newer application methods such as skid, point and slot injection are under intense review in the U. S. and the crux of this manuscript. The comparison of application technologies was initiated at several sites throughout Ohio and repeated at these same sites for at least two years. The worst case scenario of rescue treatment was used to justify the use of some treatments for comparison in this study. Eco nomic analyses consisting of cost/benefit studies were undertaken to establish the level of benefits from application machinery treat ments . To address the question of environmental friendliness, the comparison of insecticide movement by different application methodolo gies was initiated. Conclusions An understanding of spray atomization characteristics used to explain foliar deposition was imposed upon soil applications of chlorpyrifos and cyfluthrin to control the stalkborer was the central theme of Chapter I. A high and low rate as well as atomizers produc ing fine (flatfan) and coarse (flood) spray were compared in the field 154 and laboratory. In the field, the application coverage of soil sur face afforded by the fine was satisfactory enough to provide adequate control at both application rates. Only the high application rate of the soil insecticide applied by the flood nozzle provided adequate stalkborer control. In the laboratory, parameters such as coverage and droplet sizing range were investigated and used to explain what occurred in the field. In addition the behavior of the droplets on glass and soil surfaces helped to explain the discrepancies between laboratory and field studies. Lowering of rates as well as achieving adequate con trol was a function of selecting a nozzle that produced a droplet size range that provided excellent coverage of a 3-dimensional surface. This could only be accomplished by a nozzle producing a high quality, fine spray such as a flat fan. Chapter II dealt with the explaining the efficacy of granular soil insecticides on the basis with establishing the efficacy of dose acquistion via contact and volatility in addition to revealing a com plex interaction of insecticide induced attrition of carabid predators of the the black cutworm. This study was run for three continuous years, each year environmentally different than the other. Thus, an understanding of environmentally induced release of active ingredient by granules was observed. In addition, the influence of conventional 155 and no-tillage upon the dose acquistion by the black cutworm and cara bid beetle predators was observed. In the field, soil insecticides possessing high vapor pressures were not particularly effective against black cutworms, but caused significant reductions in the predatory carabid populations which could account for even greater damage. Soil insecticides with low vapor pressures tended to target specifically for black cutworms while leaving predatory carabid populations relatively undisturbed. The influence of tillage upon the release of active ingredients indicated again the transfer of dose was greater with low volatility in both conventional and no-tillage. Laboratory studies were initiated to establish the role of in trinsic toxicity against black cutworms and carabid predators. Sig nificant differences were observed between soil insecticide active ingredients which accounted for some of differential mortality between black cutworms and predatory carabids. One compound of particular interest, DPX-43898 was highly toxic to both carabids and black cut worms. However, chlorpyrifos was highly toxic to black cutworms while terbufos and fonofos were highly toxic to predatory carabids. A model demonstrated that vapor pressure, toxicity to black cutworms and cara bids were important for explaining the dose transfer process. Contact area could account for a major portion of differential toxicity, but contact area of black cutworm larvae and carabid adults was not impor tant in making the model anymore significant. In Chapters III-V, the establishment of four sites throughout Ohio was undertaken to compare the efficacy, economic and environ mental attributes of planting time, slot injection and cultivation treatments for 1987 through 1989. The importance of these sites to each study cannot be stressed enough to test application machinery under a variety of climatic and edaphic conditions that are indicative of Ohio. Further, studies such as this are testimony for the need to retain a system of outlying branches of the Ohio Agricultural Research and Development Center. In Chapter III, slot injection treatments were equal to or better than planting time application treatments. In addition, the ability to reduce rates of soil insecticide application using the slot injec tor demonstrated precisely how improved targeting could benefit both the user and society. On the other hand, slot injection also ex pounded upon the level of waste that occurs when granular soil insec ticides are applied either at planting or cultivation layby. To allay fears of exposure to a liquid soil insecticide, a dissolvable package study was initiated. All liquid soil insecticides used in these stud ies did not cause disintegration of the dissolvable bag material. To expand the comparison of application methods, operating costs were calculated for planting time and slot injection applications. This 157 information was well used for calculation of cost/benefit ratios in Chapter IV. * In Chapter IV, the establishment of a larval sampling threshold for Ohio was initiated. Two or more larvae/plant were determined to be the economic threshold for Ohio. This would not only allow mfd- season scouting to proceed but would also provide Ohio corn producers with an alternative to prophyllactic applications of granular soil insecticides should their use be banned or severely restricted. Com parison of regressions for yield loss/rootworm larvae showed no sig nificant differences were observed between the Milan and Western Branch sites, representing the Northern and Southern localities of study sites in Ohio. Once an economic threshold was established for each of the sites under study for economic threshold determination, yield differences between the untreated checks and specific treatments were used to cal culate gross benefits for the cost/benefit analysis. The cost/benefit analysis was the quotient of total operating costs in Chapter III and gross benefits for a given treatment. This not only allowed the com parison of specific soil insecticide x application methods but also compared prophylactic and scouting scenarios. Although planting time treatments exclude scouting due to their prophylactic aspect of appli cation, the gathering of efficacy information was found beneficial for future reference. In general, under years of environmental stress, 158 planting time applications without layby applications of fertilizer were economically justified. Slot injection applications at the re duced rate of 0.37 kg (AI)/ha (0.33 lb/a) were also economically bene ficial under drought conditions. In less stressful years, the reduced rate applications of slot injected soil insecticides were economical as were other application method treatments. Application of fertiliz ers was economical in wet years. Since reduced rates of soil insecti cides were economical, external costs associated with this use would be substantially less than full rate applications of planting time applications. No other economic entomology study has made use of cost/benefit ratios to compare either insecticide, application or the interaction insecticide x application method. The environmental constraints of groundwater contamination were addressed by studying the movement of the soil insecticides applied under various application scenarios in Chapter V. In addition, the different sites throughout Ohio allowed differences of soil types to be looked at in detail. Also, the soil insecticides under study pro vided a unique array of physical and chemical properties that could be used to help account for movement in the soil profile. Since movement is required for efficacious control of rootworms, this study could also help explain the performance of a soil insecticide at a given site and year. Groundwater contamination was shown not to be of concern in these innovative (targeting) studies. For the sake of brevity, the site pos sessing the greatest potential for leaching, the Milan site will be discussed. Insecticide rate did not affect the movement of slot in jection treatments. In wet years, isazophos tended to move vertically and laterly more than either chlorpyrifos or diazinon. In dry years, diazinon displayed substantial lateral movement, vertical movement was not the same magnitude as lateral movement. Chlorpyrifos tended to move immediately greater laterally and vertically more in wet than dry years. BIBLIOGRAPHY Abbott, W. S. 1925. A method for computing the effectiveness of an insecticide. J. Econ. Entomol. 18:265-267. Abdalla, M. R. and N. E. A. Scopes. 1983. ICPP Research Report 3A-R15. Abou-Assaf, N., J. R. Coats, M. E. Gray and J. J. Tollefson. 1986. Degradation of isazophos in corn fields with conservation tillage practices. J. Environ. Sci. Health. B21(6)z:425-446. Aim, S. R., D. L. Reichard and F. R. Hall. 1989. Effects of droplet size and distribution of drops containing bifenthrin on Tetranychus urticae. J. Econ. Entomol. 80:517-520. Anonymous. 1986. Hearing before FIFRA Scientific Advisory Panel on the cancellation of diazinon for use on golf courses and sod farms. USEPA, Washington D. C. May 21. Apple, J. W . , E. T. Walgenbach and J. W. Knee. 1969. Northern corn rootworm control by granular insecticide application at planting and cultivation. J. Econ. Entomol. 62:1033-1035. Apple, J. W . , H. C. Chiang, L. M. English, L. K. French, A. J. Keaster, G. F. Krause, S. M. Mayo, J. D. Munson, G. J. Musick, J. C. Owens, E. E. Rasmussen, R. E. Sechriest, J. J. Tollefson and J. L. Wedberg. 1977. Impact of northern and western corn rootworm larvae on field corn. N. Cent. Reg. Res. Publ. 239. Wis. Agric. Exp. Sta. Baker, D. B. 1985. Regional water quality impact of intensive row crop agriculture: A Lake Erie Basin Case Study. J. Soil Water Conserv. 40:125-132. Baker, J. L. and H. P. Johnson. 1979. The effect of tillage systems on pesticides in runoff from small water sheds. Trans. ASAE 22:554-559. Baker, J. L. and H. P. Johnson. 1983. Evaluating the effectiveness of BMPs from field studies, pp. 281-304. In F. W. Schaller and G. W. Bailey [eds.], Agricultural management and water quality. Iowa State Univ. Press, Ames. 160 Baker, J. L., J. M. Laflen and H. P. Johnson. 1978. Effect of tillage systems on runoff losses of pesticides, a rainfall simulation study. Trans. ASAE 21:886-892. Balcomb, r. 1983. Secondary poisoning of red shouldered hawks with carbofuran. J. Wild. Manage. 47:1129-1132. Baxter, J. F. and R. H. Hahn. 1983. Agricultural Engineers Yearbook of Standards 54:203-205. Bergman, M. K., J. J. Tollefson and P. N. Hinz. 1981. Sampling scheme for estimating populations of corn rootworm larvae. Environ. Entomol. 10:986-990. Bergman, M. K., J. J. Tollefson, and P. N. Hinz. 1983. Spatial dispersion of corn rootworm larvae in Iowa corn fields. Environ. Entomol. 12:1443-1446. Best, R. L. and C. C. Beegle. 1977. Food preferences of five species of carabids commonly found in Iowa cornfields. Environ. Entomol. 6:9-12. Blevins, R. L., C. W. Thomas, M. S. Smith, W. W. Frye and P. L. Cornelius. 1983. Changes in soil properties after 10 years continuous non-tilled and conventionally tilled corn. Soil & Till. Res. 3:135-146. Bouse, L. F. , I. W. Kirk and L. E. Bode. 1989. Proceedings of ASAE/CSAE Meeting. Quebec, Canada. Branson, T. F., G. R. Sutter and J. R. Fischer. 1982. Comparison of tolerant and a susceptible maize inbred under artificial infestations of Diabrotica virgifera virgifera : yield and adult emergence. Environ. Entomol. 11:371-372. Briggs, G. G. 1981. Theoretical and experimental relationships between soil adsorption, octanol-water partition coefficients, water solubilities, bioconcentration factors, and the parachor. J. Agric. Food. Chem. 29:1050-1059. Brust, G. E., B. R. Stinner and D. A. McCartney. 1985. Tillage and soil insecticide effects on predator-black cutworm (Lepidoptera: Noctuidae) interactions in corn agroecosystems. J. Econ. Entomol. 78:1389-1392. Brust, G. E. , B. R. Stinner and D. A. McCartney. 1986. Predation by soil inhabiting arthropods in intercropped and monoculture agroecosystems. Agric. Ecosys. Environ. 18:145-154. 162 Burkhardt, C. C. and M. L. Fairchild. 1967. Bioassay of field treated soils to determine bioactivity and movement of insecticides. J. Econ. Entomol. 60:1602-1610. Cardwell, V. B. 1982. Fifty years of Minnesota corn production: sources of yield increase. Agron. Jour. 74:985-990. Casey, J. E., R. D. Lacewell and W. Sterling. 1975. An example of economically feasible opportunities for reducing pesticide use in commercial agriculture. J. Environ. Qual. 4:60-64. Cashman, C. M., M. A. Martin and B. A. McCarl. 1981. Economic consequences of bans on corn ( Z e a m a y s ) and soybean (Glycine max ) herbicides commonly used on Indiana farms. Weed Sci. 29:323-228. Chichester, F. W . , J. E. Morrison and T. J. Gerik. 1989. Minimum disturbance fertilizer knifing for No-Till. Trans. ASAE 28:1013-1018. Clapp, J., M. K. Bergman and L. W. Bledsoe. 1985. Evaluation of the nutiblast as a method for applying insecticide-urea solutions on continuous corn. Arcadian Technical Report No. 12. Clement, S. L. and D. A. McCartney. 1982. Black cutworm (Lepidoptera: Noctuidae): measurement of larval feeding parameters on field corn in the greenhouse. J. Econ. Entomol. Coaker, T. H. and D. H. Williams. 1963. The importance of some carabidiae and staphylinidae as predators of the cabbage root fly, Erosia brassicae (Bouche’). Ent. Exp. Appl. 6:156-164. Cochran. W. G. and G. M. Cox. 1957. Experimental designs, 2nd ed. John Wiley & Sons, Inc. New York. Croft, B. A. 1982. Arthropod resistance to insecticides: a key to pest control failures and successes in North American apple orchards. Entomol. Exp. Appl. 31:88-110. Critchley, B. R. 1972. A laboratory study of the effects of some soil applied organophosphorus pesticides on Carabidae (Coleoptera). Bull. Entomol. REs. 62:229-242. Davis, P. M. and L. P. Pedigo. Action threshold for the stalk borer Environ. Entomol. 18:In Press. Duncan, D. B. 1955. Multiple range and multiple F. tests. Biometrics 11:1-41. Durest, D. D. and E. T. Black. 1977. Changes in Farm Production and Efficiency, USDA-ERS SR-581. 163 Edwards, C. R. and F. T. Turpin. 1989. Managing Corn Rootworms-1989. Purdue University Cooperative Extension Service, E-49. Ellenberger, J. 1989. Carbofuran: Special review technical support document. EPA Pos. Doc. 2/3. Ellis, C. R. 1982. A survey of granular application equipment, and insecticide rates for control of corn rootworms. Proceedings of the Entomological Society of Ontario 113:29-34. Erbach, D. C. and J. J. Tollefson. 1983. Granular insecticide application for corn rootworm control. Trans. ASAE 10:696-699. Felsot, A. S. 1987. Fate and interactions of pesticides in conservation tillage systems In Arthropods in conservation tillage systems. Entomol. Soc. Amer. 65:1-52. Felsot, A. S., W. N. Bruce and K. S. Steffey. 1987. Degradation of terbufos soil insecticide in corn fields under conservation tillage practices. Bull. Environ. Contam. Toxicol. 38:369-376. Frank, J. H. 1971. Carabidae (Coleoptera) as predators of the red- backed cutworm (Lepidoptera: Noctuidae) in central Alberta. Can. Entomol. 103:1039-1044. Ford, M. G. and D. W. Salt. 1983. Crit. Rev. Appl. Chem. 23:26-81. Foster, R. E. and J. J. Tollefson. 1986. Frequency and severity of attack of several pest insects of corn in Iowa. J. Kan. Entom. Soc. 59:269-274. Foster, R. E., J. J. Tollefson, J. P. Nyrop and G. L. Hein. 1986. Value of adult corn rootworm population estimates in pest management decisionmaking. J. Econ. Entomol. 79:303-310. Gholson, L. e., C. C. Beegle, R. L. Best and J. C. Owens. 1978. Effects of several commonly used insecticides on cornfield carabids in Iowa. J. Econ. Entomol. 71:416-418. Getzin, L. W. 1985. Factors influencing the persistence and effectiveness of chlorpyrifos in soil. J. Econ. Entomol. 78:4120418. Gordon, R. F. S., K. T. Atcock and A. R. Jutsum. 1989. Soil-applied insecticides: Comparability of performance between laboratory and field. Aspect. Appl. Biol. 21:107-117. Graham-Bryce, I. J. 1983. Pesticide research for improvement of human welfare. Proceedings of the Fifth International Congress of Pesticide Chemistry 1:21-42. 164 Gray, M. E. and J. J. Tollefson. 1987. Influence of tillage and western and northern corn rootworm (Coleoptera: Chrysoraelidae) egg populations and root damage. J. Econ. Entomol. 80:911-915. Hall, F. R. and J. P. Reed. 1988. Improved biotargeting of soil applied pesticides. Application to seeds and soil. BCPC Monograph No. 39:351-361. Hall, F. R . , D. L. Reichard and S. R. Aim 1987. A system for the examination of the pesticide dose transfer process. Pesticide formulations and the pesticide dose transfer process. 7:85-92. Harris, C. R. 1969. Laboratory evaluation of candidate materials as potential soil insecticides. J. Econ. Entomol. 63:7820787. Harris, C. R. 1972. Factors influencing the effectiveness of insecticides. Ann. Rev. Entomol. 17:177-198. Harris, C. R. and H. J. Svec. 1968. Toxicological studies on cutworms. Laboratory investigations on the toxicity of insecticides to the black cutworm, with special reference to the influence of soil type, soil moisture method of application, and formulation on insecticide activation. J. Econ. Entomol. 61:965-969. Hibbard, B. E. and L. B. Bjostad. 1989. Corn semi chemicals on insecticide efficacy and insecticide repellency toward western corn rootworm larvae. J. Econ. Entomol. 82:773-781. Hills, T. M. and D. C. Peters. 1971. A method of evaluating post planting insecticide treatments for control of western corn rootworm larvae. J. Econ. Entomol. 64:764-765. Horn, D. J. 1988. Ecological approach to pest management. Chap. 3: 35-61. Guilford Press, N. Y . , New York. Hoy, M. A. 1987. Developing insecticide resistance in insect and mite predators and opportunities for gene transfer, pp. 125-138. In H. M. LeBaron, R. 0. Mumma, R. C. Honeycutt and J. H. Duesing [eds], Biotechnology in agricultural chemistry. American Chemical Society Symposium Series No. 334. Hull, L. A. and E. H. Beers. 1985. Ecological selectivity: modifying chemical control practices to preserve natural enemies, pp. 103-121. In M. A. Hoy and D. C. Herzog [eds]. Biological control in agricultural IPM systems iiu 0— L OrlaNdo, j? 1BH Johnstone, D. R. Pesticide Formulations (ed. Valkenburg, W. van) New York, N. Y. Marcel Dekker., pp. 625. (1973). Jordan, V. W. L. and G. R. Stinchcombe. 1988. Cost benefits of integrating nitrogen, plant growth regulations and fungicides in winter barley. Crop Prot. 7:252-257. Karr, L. L. and J. J. Tollefson. 1987. Durability of Pherocon AM trap for adult western and northern corn rootworm sampling. J. Econ. Entomol. 80:891-896. Kenaga, E. E. and C. A. I. Goring. 1980. Relationship between water solubility, soil adsorption, octanol-water partitioning, and concentration of chemicals in biota. ASTM Special Publ. 707:78-115. Knight, F. H. 1921. Risk, uncertainty, and profit. Boston: Houghton Mifflin Co. 312 pp. Kuhlman, D. K. 1984. Why soil insecticides don't work. Solutions 5: 57-65. Kuhr, R. J. and H. Tashiro. 1978. Distribution and persistence of chlorpyrifos and diazinon applied to turf. Bull. Environ. Contam. Toxicol. 20:652-656. Lichtenstein, E. P. and K. R. Shulz. 1964. The effects of moisture and microorganisms on the persistence and metabolism of some organophosphate insecticides in soils with special emphasis on parathion. J. Econ. Entomol. 57:618-627. Lichtenstein, E. P., T. W. Fuhreman, K. R. Schulz and T. T. Liang. 1973. Effect of field application methods on the persistence and metabolism of phorate in soil and its translocation into crops. J . Econ. Entomol. 66:863-866. Lilly, J. H. and H. Gunderson. 1952. Fighting the corn rootworm. Iowa Farm Sci. 6:18-19. Lockertz, W. E., G. Shearer, S. Sweeney, G. Kuepper, D. Winner and D. E. Kohl. 1980. Maize yields and soil nutrient levels with and without pesticides and standard commercial fertilizers. Agron. Jour. 72:65-72. Lund, R. D. and F. T. Turpin. 1977. Serological investigation of black cutworm consumption by ground beetles. Ann. Entomol. Soc. Amer. 70:322-324. Matthews, G. A. 1985. Pesticide Application Methods. New York, N. Y. Longman Group Ltd., pp. 325. Mayo, Z. B. 1976. Emergency post-planting applications of insecticides to control larvae of the western and northern corn rootworm in Nebraska. J. Econ. Entomol. 69:600-602. Mayo, Z. B. 1976. Control of the western and northern corn rootworm with liquid starter fertilizer-insecticide combinations and the influence of depth of placement. J. Econ. Entomol. 70:234-236. Mayo, Z. B. and L. L. Peters. 1978. Planting vs. cultivation time applications of granular soil insecticides to control larvae of corn rootworms in Nebraska. J. Econ. Entomol. 71:801-803. McDonald, D. 1987. Chemicals and your health. Farm Journal 3:8-11. Metcalf, R. L. 1980. Changing role of insecticides in crop protection. Ann. Rev. Entomol. 25:219-256. Metcalf, R. L. 1986. Foreward, pp. vii-xv. In J. L. Krysan and T. A. Miller [eds.], Methods for the study of pest Diabrotica. Springer-Verlag, New York. Miller, A. 1987. Dimensionally stable water soluble pouches for safety. Eight Symposium on Pesticide Formulations and Application Systems. ASTM. IN PRESS. Mullin, C. A. and B. A. Croft. 1985. An update on the development of selective and biodegradable pesticides, pp. 123-150. In M. A. Hoy and D. C. Herzog [eds], Biological control in agriculture. IPM systems. Academic, ORlando, Fla. Munthali, D. C. 1984. Biological efficacy of small dicofol droplets against Tetranychus urticae eggs, larvae and protonymphs. Crop Protection 3:327-334. Musick, G. J. 1970. Influence of conservation tillage on field crop insect pests. Proc. N. E. No-Till Conference. 1:44-59. Musick, G. J. 1974. Efficacy of liquid starter fertilizer combinations for control of resistant northern corn rootworm larvae. J. Econ. Entomol. 67:668-670. Naranjo, S. E. and A. J. Sawyer. 1988. Impact of host phenology on the population dynamics of northern cron rootworms in field corn. Environ. Entomol. 17:508-521. Niemczyk, H. D. and H. R. Krueger. 1982. Binding of insecticides on turfgrass thatch, pp. 61-63. In H. D. Niemczyk and B. G. Joyner [eds.], Advances in Turfgrass Entomology. Chemlawn Corp., Worthington, OH. Niemczyk, H. D., and H. R. Krueger. 1987. Persistence and mobility of isazophos in turfgrass thatch and soil. J. Econ. Entomol. 80(4):950-952. Osteen, C. and F. Kuchler. 1986. Potential bans of corn and soybean pesticides: Economic implications for farms and consumers. USDA-ERS. AER-546. Osteen, C. J. and L. Suguiyama. 1988. Losing chlordimeform use in cotton production. U. S. Dep. Agric., Econ. Res. Serv. AER-546. Ozkan, H. E., D. L. Reichard, H. D. Niemczyk, M. G. Klein and H. R. Krueger. 1989. Subsurface point injector applicator for turfgrass insecticides. Trans. ASAE. (In Press). Palmer, A., I. A. Wyatt and N. E. A. Scopes. ICPP Research Report SA RIS. (1983). Peters, D. C. 1975. Value of soil insect control in Iowa corn, 1951- 1970. J. Econ. Entomol. 68:483-486. Petty, H. B., D. E. Kuhlman and R. E. Sechriest. 1969. Corn yield losses correlated with rootworm larval populations, In Proceed. NCB-ESA 24:141-142. Pimentel, D. and L. Levitan. 1986. Pesticides: amounts applied and amounts reaching pests. BioScience 36:86-91. Read, D. C. 1976. Comparison of residual toxicity of 24 registered or candidate pesticides applied to field microplots of soil by different methods. J. Econ. Entomol. 69:429-437. Reed, J. P., R. J. Kremer and A. J. Keaster. 1987. Characterization of microorganisms in soils exhibiting accelerated pesticide degradation. Bull. Environ. Contam. Toxicol. 39:776-782. Reed, R. M. , F. P. Gross, R. B. Fox and J. McManus. 1987. 1 2 ^ ed. Equipment investment analysis, Caterpillar Tractor Co. Peoria, IL. 1-56. Reed, J. P., F. R. Hall, H. R. Krueger and D. L. Reichard. 1988. An assessment of slot injected soil insecticides for corn rootworm control. Abstracts NCB-ESA, Denver, CO. Reed, J. P., R. J. Kremer, A. J. Keaster and H. D. Kerr. 1989. Microbial degradation of some soil insecticides, herbicides and insecticide-herbicide combinations. Bull. Environ. Contam. Toxicol. 42:676-681. Reichard, D. L. and T. L. Ladd. 1983. Pesticide injection and transfer system for field sprayers. Trans. ASAE 26:683-686. Rider, A. R. and E. C. Dickey. 1982. Field evaluation of calibration accuracy for pesticide application equipment. Trans. ASAE 25:258-260. Robertson, J. L. K. C. Smith, N. E. Savin and R. J. Lavigne. 1984. Effects of dose selection and sample size on the precision of lethal dose estimates in dose-mortality regression. J. Econ. Entomol. 77:833-837. Ruppel, R. F. 1984. Model for effective timing of an insecticide. J. Econ. Entomol. 77:1083-1085. SAS Institute. 1982 SAS user's guide: basics. SAS Institute, Cary, Schmidt, B. J. 1981-82. Agronomy Guide. Oh. Coop. Ext. Serv. Bull. 472. 93 pp. Sears, M. K. and R. A. Chapman. 1979. Persistence and movement of four insecticides applied to turfgrass. J. Econ. Entomol. 72(2):272-274. Sheehan, W. 1986. Response by specialist and generalist natural enemies to agroecosystem diversification: a selective review. Environ. Entomol. 15:456-461. Shepard, H. H. Methods of Testing Chemicals on Insects. Minneapolis, MN. Burgess Publ., pp.355. (1955). Singh, G. Z. Singh and T. S. Kathpal. 1984. Method of application affecting phorate persistence in soil and its translation into cotton plants. Indian J. Ent. 46:183-186. Solie, J. B., H. S. Witmus and 0. C. Burnside. 1983. Improving weed control with a subsurface jet injector system for herbicide. Trans. ASAE 27:1724-1728. Southwood, T. R. E. 1986. Ecological methods with particular reference to the study of insect populations. First ed. Chapman and Hall, London. 391 pp. Spike, B. P. and J. J. Tollefson. 1988. Western corn rootworm larval survival and damage potential to corn subjected to nitrogen and plant density treatments. J. Econ. Entomol. 81:1450-1455. Stamm, D. E., Z. B. Mayo, J. B. Campbell, J. F. Witkowski, L. W. Anderson and R. Kozub. 1985. Western corn rootworm (Coleoptera: Chrysomelidae) beetle counts as a means of making larval control recommendations in Nebraska. J. Econ. Entomol. 78:794-798. Stemerhof, M. 1987. The economics of herbicide use on corn and soybeans in southwestern Ontario. A Final Report for the Ontario Pesticides Advisory Committee. Ont. Min. Environ., Toronto. Stemerhof, M . , C. J. Swanton, A. S. Hamill and R. H. Brown. 1988. Economics of herbicide use on corn and soybeans in Ontario. Weed Sci. 2:466-472. Stern, V. M. , R. F. Smith, R. van den Bosch and K. S. Hagen. 1959. The integrated control concept. Hilgardia 29:81-101. Stinner, B. R., D. A. McCartney and W. L. Rubink. J. Ga. Entomol. Soc. (1984). Stinner, B. R., H. R. Krueger, D. A. McCartney. 1986. Insecticide and tillage effects on pest and non-pest arthropods in corn agroecosystems. Agric. Ecosys. Environ. 15:11-21. Story, R. N. and A. J. Keaster. 1982. Development and evaluation of a larval sampling technique for the black cutworm. J. Econ. Entomol. 12:241-244. Story, R. N., A. J. Keaster, W. B. Showers, J. T. Shaw and V. Wright. 1983. Economic-threshold dynamics of black and claybacked cutworms (Lepidoptera: Noctuidae) in field crops. 13:131-137. Strnad, S. P. and M. K. Bergman. 1987. Movement of first-instar western corn rootworms in soil. J. Econ. Entomol. 16:975-978. Suett, D. L. 1988. Application to seeds and soil: recent developments, future prospects and potential limitations. In: Pests and Diseases. 2:823-832. Suguiyama, L. F. and G. A. Carlson. 1985. Field crop pests: farmers report the severity and intensity. USDA-ERS, AI-487. Sutter, G. R. 1982. Comparative toxicity of insecticides for corn rootworm larvae in a soil bioassay. J. Econ. Entomol. 75:489-491. Swann, R. L. and A. Eschenroeder. 1983. Fate of chemicals in the environment. ACS Symp. Ser. 225. Amer. Chem. Soc., 320 pp. Taylor, L. R. 1961. Aggregation, variance, and the mean. Nature (London) 189:732-735. Thompson, A. R., H. R. Howse and G. W. Edmonds. 1988. Liquid insecticides and fertilizer treatments applied under seed at sowing: aspects of their performance and relevance to systems of reduced-input, sustainable agriculture. In: Pests and Diseases. 2:845-852. Tollefson, J. J., G. L. Hein and J. D. Oleson. 1987. Influence of application technique on insecticidal control of corn rootworm in three tillage systems. Down to Earth 43:16-18. Tomlin, A. D. 1975. The toxicity of insecticides by contact and soil treatment to two species of ground beetles. Can. Ent. 107:529-532. Trevors, J. T. 1986. A basic program for estimating LD50 values using the IBM-PC. Bull. Environ. Contam. Toxicol. 37:18-26. Turpin, F. T., L. C. Dumenil and D. C. Peters. 1972. Edaphic and agronomic characters that affect potential for rootworm damage to corn in Iowa. J. Econ. Entomol. 65:1615-1619. Turpin, F. T. and J. M. Thieme. 1977. Impact of soil insecticide usage on corn production in Indiana: 1972-1975. J. Econ. Entomol. 71:83-86. Uk, S. and R. J. Courshee Pestic. Sci. 13:529-536. (1982). Urbain, C. D. 1989. EPA may ban Furadan. Farm Journal 3:29. USDA-ERS. 1989. Agricultural Outlook, USDA-ERS, AO-156. Waldron, A. 1989. Personal Communication. Walker, P. T. 1971. The use of granular pesticides from the point of view of residues. Res. Rev. 40:64-132. Wauchope, R. D. 1978. The pesticide content of surface water draining from agricultural fields-a review. J. Environ. Qual. 7:459-472. Wauchope, R. D. and R. A. Leonard. 1980. Maximum pesticide concentrations in agricultural runoff: a semiempirical prediction formula. J. Environ. Qual. 9:665-672. Wearing, C. H. 1988. Evaluating the IPM implementation process. Ann. Rev. Entomol. 33:17-38. Weiss, M. J. and Z. B. Mayo. 1983. Potential of corn rootworm (Coleoptera: Chrysomelidae) larval counts to estimate larval populations to make control decisions. J. Econ. Entomol. 76:158-161. Whitehead, A. G. 1983. Application of pesticides to the seedbed be vertical band technique. In: Tenth International Congress of Plant Protection: Plant Protection for Human Welfare 2, 522. Worthing, C. R. and S. B. Walker. 1987. The pesticide manual compendium, 8^ edition. BCPC. APPENDIX 173 Table 33. Lateral movement of soil insecticides at the Bluffton site, 1987 (ppm). 0.37 ke (AI)/ha 1.12 ke (AI)/ha 4 July 28 July 4 July 28 July Treatment A B ABA B A B Chlorpyrifos 5.3 1.1 0.5 0.4 8.6 7.2 1.1 1.0 Diazinon 3.8 0.6 0.7 0.5 7.8 0.8 1.6 0.7 Isazophos 6.5 0.2 0.4 0.2 7.4 0.3 1.2 0.3 174 Table 34. Movement of soil insecticides in conventional and no-till plots at the Wooster site in 1987 (ppm). Conventional Tillage 0.37 kg (AI)/ha 1.12 (AI)/ha 13 July 4 August 13 July 4 August Treatment A B A B A B A B Chlorpyrifos 1.5 0.0 1.1 0.1 5.1 3.3 4.4 1.6 Diazinon 1.8 0.1 0.1 0.0 10.1 1.6 6.5 0.1 Isazophos 2.1 1.2 1.5 0.0 10.3 2.1 6.6 0.0 No-Tillage 0.37 kg (AI)/ha 1.12 (AI)/ha 13 July 4 August 13 July 4 August Treatment A B A B A B A B Chlorpyrifos 2.5 0.3 1.3 0.1 3.4 0.4 1.4 0.0 Diazinon 1.2 0.0 0.0 0.0 4.2 0.0 1.9 0.0 Isazophos 2.3 0.4 1.5 0.8 3.5 0.0 2.7 0.3 Table 35. F-values and P>F of insecticide x sampling method ofr various application methods at four sites in 1988. 1988 Planting Time 1.12 kg/ha Injection 1.12 kg/ha Injection 0.37 kg/ha Site ______F-value P>F F-value______P>F______F-value______P>F Wooster 646.12 0.0000 892.00 0.0000 335.00 0.0000 Bluffton 19.18 0.0000 420.86 0.0000 10.12 0.0001 Western Branch 53.47 0.0000 7.33 0.0002 Milan 5.66 0.0000 407.59 0.0000 5.84 0.0003 Table 36. F-values and P>F of insecticide x sampling methods for various methods at three sites in 1989. ______1989______ Planting Time 1.12 kg/ha Injection 1.12 kg/ha Injection 1.12 kg/ha Site______F-value______P>F______F-value______P>F______F-value______P>F Wooster 458.90 0.0000 1084.74 0.0000 921.60 0.0000 Western Branch 48.05 0.0000 15.47 0.0000 Milan 9.44 0.0001 23.85 0.0000 103.75 0.0000 Table 37. Soil sampling date for residue analysis of soil insecticides applied at four sites in 1988. Planting Time Site Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 20 May 28 May 8 June 21 June 25 July Bluffton 13 May 21 May 30 May 15 June 18 July Western Branch Milan 15 May 23 May 2 June 18 June 18 July In.i ection Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 30 June 6 July 14 July 30 July 27 August Bluffton 28 June 4 July 12 July 27 July 1 September Western Branch 15 June 23 June 30 June 15 July 20 August Milan 22 June 28 June 5 June 18 June 18 July 178 Table 38. Soil sampling date for residue analysis of soil insecticides applied at four sites in 1989. Planting Time Site Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 18 May 27 May 6 June 18 June 16 August Western Branch Milan 17 May 25 May 2 June 19 June 8 August Inlection Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 11 June 18 June 28 June 16 August 20 September Western Branch 24 June 2 July 9 July 27 July 5 September Milan 7 July 15 July 21 July 8 August 12 September Table 39. Agronomic and edaphic factors for the evaluation of various soil insecticide application methods. i Wooster-1- Bluffton5 Western Branch5 Milan^ Soil Series Wooster SiL Pewamo SiCl Brookston SiCl Tuscola SaL Tillage CT/NT CT MT CT Corn Var. Illini Chief Dekalb T1100 Pioneer 3377 Sx625 Planting Date 15 May3 1 June-3 ------20 May6 13 May6 20 April6 13 May6 18 May7 - - - 19 May7 17 May7 Larval Sampling Date . . . 21 June6 30 June6 18 June6 ------19 June7 25 June7 Cultivation 21 June-* 30 June5 ... _ _ „ 25 June6 15 June6 ------1 July7 ------ Injection 23 June-* 30 June5 £ 30 June 28 June® 15 June6 22 June6 11 June7 - - - 24 June7 6 July7 ... Root Rating 30 July5 12 July5 £ 30 July6 13 July6 20 July6 18 July6 23 July7 - - - 21 July7 22 July7 Yield - - - 20 Sept6 24 Sept6 22 Sept6 6 Sept7 8 Sept7 ■^-Wooster-Canfield Silt-Loam; Conventional and No-Tillage ^Pewamo-Blount Silty-Clay; conventional Tillage 5Brookston-Cosby Silty-Clay-Loam; Minimum Tillage ^Tuscola Sandy-Loam; Conventional Tillage 51987 Wooster and Bluffton Only 61988 All Four Sites Planted 71989 Bluffton Not Planted Due to Rain 180 Table 40. Water solubility (ppm), vapor pressure (kPa), mammalian toxicity and GUS values of chlorpyrifos, diazinon and isazophos. Property______Chlorpyrifos Diazinon Isazophos Water Solubility 2.0 40 250 Vapor Pressure 2.5 0.097 4.3 Mammalian Toxicity (Rat, acute oral) 150 350 50 GUS value 0.31 2.0 2.8 Improbable leacher Transition, leachers 181 Table 41. Cumulative precipitation [in] and (air temperature [°F]) for soil sampling periods at four sites in 1988. Planting Time Site Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 2.10 (72) 1.03 (80) 0.90 (82) 0.41 (83) 5.65 (87) Bluffton 1.30 (75) 0.23 (83) 0.00 (87) 0.15 (88) 0.00 (81) Western Branch Milan 0.00 (73) 0.0 (72) 0.33 (74) 0.78 (83) 0.93 (87) Inj ection Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 0.00 (73) 0.69 (82) 0.04 (84) 5.29 (86) 2.37 (82) Bluffton 0.18 (89) 0.00 (91) 0.09 (88) 0.00 (95) 1.09 (91) Western Branch 1.87 (85) 0.28 (85) 1.20 (90) 1.35 (98) 7.05 (93) Milan 0.93 (85) 0.00 (86) 0.00 (92) 1.55 (97) 1.93 (92) Table 42. Cumulative precipitation [in] and (air temperature [°F]) for soil sampling periods at these sites in 1989. Planting Time Site Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 3.54 (65) 7.52 (67) 6.78 (71) 2.69 (70) 0.88 (68) Western Branch Milan 7.65 (69) 3.76 (71) 4.64 (74) 2.24 (77) 6.21 (74) Inlection * Date 1 Date 2 Date 3 Date 4 Date 5 Wooster 1.84 (72) 1.30 (69) 1.02 (70) 1.53 (72) 0.29 (70) Western Branch 0.05 (75) 0.32 (73) 0.86 (74) 1.07 (71) 0.05 (77) Milan 2.12 (73) 0.00 (68) 0.37 (69) 0.08 (75) 0.00 (77)