AN ABSTRACT OF THE THESIS OF
John J. Hadam for the degree of Master of Science in
Entomology presented on December 6, 1985.
Title: Phytoseiid Mites (Parasitiformes:Phytoseiidae) of Commercial Crops in the Willamette Valley, Oregon and
Pesticide Resistance in the Principal Species Typhlodro- mus pyri Scheuten. Redacted for Privacy Abstract approved: Mohammed T. AliN azee Redacted for Privacy Brian A. Croft
A survey of 13 Willamette Valley commercial crops
found Typhlodromus pyri Scheuten to be the principal
phytoseiid on most crops. Typhlodromus occidentalis Nesbitt, Amblyseius andersoni (Chant), Amblyseius
aberrans (Oude.), Typhlodromus arboreus Chant and
Amblyseius fallacis (Garman) were also collected fre,'"
quently. T. pyri was most prevalent on apple, prune, grape and blackberry and usually in crops receiving low num-
bers of insecticide treatments. No significant seasonal
differences in abundance were observed although T. pyri
numbers did decline during late season. T. occidentalis was significantly more abundant on apple and cherrythan
on other crops, being most prevalent late in the season and in highly sprayed regimes. A. andersoni was wide- spread among crops and throughout the season but was mostly limited to sites receiving few insecticide applications. Of the species not tested statistically, A. aberrans was most abundant on filbert while A. fallacis was the dominant species collected on strawberry.
T. arboreus was locally common on apple and prune but not as abundant in the valley as earlier presumed. Resistance tests of Oregon T. pyri strains using a slide-dip technique showed moderate resistance to azin- phosmethyl (5-7 fold) and high resistances to carbaryl
(25-28 fold) and parathion (ca. 100 fold). PHYTOSEIID MITES (PARASITIFORMES:PHYTOSEIIDAE) OF COMMERCIAL CROPS IN THE WILLAMETTE VALLEY, OREGON AND PESTICIDE RESISTANCE IN THE PRINCIPAL SPECIES Typhlodromus pyri Scheuten
by
John J. Hadam
A THESIS
submitted to
Oregon State University
in partial fulfillment of the requirements for the degree of Master of Science
Completed December 6, 1985
Commencement June 1986 APPROVED: Redacted for Privacy
Professor of En-gbrhology in charge of major Redacted for Privacy Professor of Entomology ifrcharge of major Redacted for Privacy /C:;r4--e-f-- "7 - Head of Department of Ento ogy
A Redacted for Privacy Dean of Grad to Scho
Date thesis presented December 6, 1985 Acknowledgements
I express my utmost thanks to Drs. Brian Croft and
M. T. AliNiazee for their support, valuable advice, constructive critisism and patience during my term of study.
I would also like to thank Dr. Dave McIntire, Dr. Gerald Krantz, Steven Booth and Gary Parsons for their timely help and advice. Finally, my grateful thanks to my wife, Diana, and the rest of the family for their never-ending support and encouragement. TABLE OF CONTENTS
Page
INTRODUCTION 1
LITERATURE REVIEW 4
METHODS 14 Area and Crops Under Study 14 Sampling and Classification Techniques 14 Statistical Analysis 18 T. pyri Resistance Test Techniques 19
RESULTS 23 Species Distribution 23 Insecticide Resistance in T. pyri 53
DISCUSSION 63 Typhlodromus pyri 63 Typhlodromus occidentalis 70 Amblyseius andersoni 73 Amblyseius aberrans 74 Typhlodromus arboreus 75 Amblyseius fallacis 76 Amblyseius 'complex' 77 Mite Management in the Willamette Valley 78
LITERATURE CITED 82
APPENDICES 94 LIST OF FIGURES
Figure Page
1. Area of phytoseiid mite survey, including locations where T. pyri strains were col- lected for resistance testing. 15
2. Relative abundance of phytoseiid mites on surveyed commercial crops of the Willamette Valley, Oregon. 24
3. Collection locations in Willamette Valley, Oregon, by crop, of T. pyri. 26
4. Collection locations in Willamette Valley, Oregon, by crop, of T. occidentalis. 27
5. Collection locations in Willamette Valley, Oregon, by crop, of A. andersoni. 29
6. Collection locations in Willamette Valley, Oregon, by crop, of A. aberrans. 30
7. Collection locations in Willamette Valley, Oregon, by crop, of T. arboreus. 31
8. Collection locations in Willamette Valley, Oregon, by crop, of A. fallacis. 32
9. Collection locations in Willamette Valley, Oregon, by crop, of T. rhenanoides. 33
10. Collection locations in Willamette Valley, Oregon, by crop, of Amblyseius 'complex'. 34
11. Distribution of phytoseiids during growing season on commercial crops of the Willamette Valley, Oregon. 40
12. Distribution between spray regimes of phytoseiids collected on Willamette Valley, Oregon commercial crops. 47
13. Azinphosmethyl 48-hour lethal concentration response curves of strains of T. pyri occurring in Willamette Valley, OR and Hood River, OR. 56
14. Carbaryl 48-hour lethal concentration res- ponse curves of strains of T. pyri occurring in Willamette Valley, OR and Hood River, OR. 58 Figure Page
15. Parathion 48-hour lethal response curves of strains of T. pyri occurring in Willamette Valley, OR and Hood River, OR. 61
16. Dorsal shield of Typhlodromus sp., show- ing chaetotactic nomenclature 97
17. Dorsal shield of Amblyseius sp., showing chaetotactic nomenclature 97
18. Typhlodromus arboreus: dorsal shield 98
19. Typhlodromus arboreus: ventrianal shield 98
20. Typhlodromus rhenanoides: dorsal shield 99
21. Typhlodromus rhenanoides: ventrianal shield 99
22. Typhlodromus pyri: dorsal shield 100
23. Typhlodromus pyri: ventrianal shield 100
24. Typhlodromus occidentalis: dorsal shield 101
25. Typhlodromus occidentalis: ventrianal shield101
26. Amblyseius aberrans: dorsal shield 102
27. Amblyseius aberrans: ventrianal shield 102
28. Amblyseius andersoni: dorsal shield 103
29. Amblyseius andersoni: ventrianal shield 103
30. Amblyseius fallacis: dorsal shield 104
31. Amblyseius fallacis: ventrianal shield 104
32. Amblyseius umbraticus: dorsal shield 105
33. Amblyseius umbraticus: ventrianal shield 105
34. Amblyseius brevispinus: dorsal shield 106
35. Amblyseius brevispinus: ventrianal shield 106
36. Amblyseius brevispinus: chelicera showing denticle on moveable digit 106 Figure Page
37. Amblyseius zwoelferi: dorsal shield 107
38. Amblyseius zwoelferi: ventrianal shield 107
39. Amblyseius zwoelferi: spermatheca 107
40. Amblyseius reticulatus: dorsal shield 108
41. Amblyseius reticulatus: ventrianal shield 108
42. Amblyseius reticulatus: spermatheca 108 LIST OF TABLES
Table Page
1. Sampling sites in Willamette Valley, Oregon survey of phytoseiid mites classified by crop and spray intensity. 17
2. Collection locations for five strains of T. pyri used in resistance tests. 20
3. Results of Kruskal-Wallis tests checking for significant differences in abundance between crops of T. pyri. 36
4. Results of Kruskal-Wallis tests checking for significant differences in abundance between crops of T. occidentalis. 37
5. Results of Kruskal-Wallis tests checking for significant differences in abundance between crops of A. andersoni. 38
6. Assessment of temporal trends of phytoseiid species T. pyri, T. occidentalis and A. andersoni on Willamette Valley crops, based on Kruskal-Wallis tests. 45
7. Assessment of impact of spray regime on abundance of phytoseiid species T. pyri, T. occidentalis and A. andersoni on Willamette Valley crops, based on Jonckheere-Terpstra tests. 52
8. Susceptibility of T. pyri collected from different locations in Oregon to azin- phosmethyl. 55
9. Susceptibility of T. pyri collected from different locations in Oregon to carbaryl. 57
10. F-test for comparison of similar LCP lines of T. pyri collected from different locations in Oregon. 59
11. Susceptibility of T. pyri collected from different locations in Oregon to parathion. 62 PHYTOSEIID MITES (PARASITIFORMES:PHYTOSEIIDAE) OF COMMERCIAL CROPS IN THE WILLAMETTE VALLEY, OREGON AND PESTICIDE RESISTANCE IN THE PRINCIPAL SPECIES Typhlodromus pyri Scheuten
INTRODUCTION
Spider mites (Acariformes:Tetranychidae) are common pests of commercial crops grown worldwide (van de Vrie et al., 1972; Jeppson et al., 1975). Integrated pest management (IPM) programs utilizing phytoseiid mites
(Parasitiformes:Phytoseiidae), selective pesticides and cultural controls have been developed to maintain these acarine pests below economically damaging levels, especially in tree fruit crops (Hoyt, 1969; Croft, 1975a;
Wearing et al., 1978; Weires et al., 1979).
Integrated mite management programs developed in California (Croft & Barnes, 1971; Kinn & Doutt, 1972; Hoy et al., 1984) and Washington (Hoyt, 1969) have utilized predaceous phytoseiid mites. Research on mite IPM in Oregon is more limited, as is previous research on the predatory Phytoseiidae of the state. For example, Jorgensen (1964) found Typhlodromus rhenanus (Oude.) the most common phytoseiid in semi-commercial apple orchards in the Hood River Valley. Jorgensen's work was mostly ecological, dealing with predator-prey relationships.
Zwick (1972) found Typhlodromus occidentalis Nesbitt abundant in commercial orchards in Hood River but con- sidered it incapable of adequately controlling Tetranychus 2 urticae Koch, Tetranychus mcdanieli McGregor and
Panonychus ulmi (Koch) in the field. Westigard (1971) had some success using T. occidentalis as part of an IPM program for pest mites of commercial pear in the Rogue River Valley.
The Willamette Valley, another major agricultural area in Oregon, has had only cursory surveys of the
Phytoseiidae taken from its commercial crops. The valley, situated between the coastal and Cascade mountain ranges in western Oregon, provides ca. 50% of the agricultural income and ca. 29% of the harvested acreage of the state
(Anonymous, 1984a). Its maritime climate and fertile soils support a great diversity of crops. Spider mites attack several of these crops, including mint, corn, vegetables and a number of tree fruits and nuts (van de
Vrie et al., 1972). The only study of phytoseiid mites in the Willamette Valley was by AliNiazee (1979a,b), who found Typhlodromus arboreus Chant common in sprayed apple orchards. He concluded that T. arboreus was effective in controlling several mite pests at the speci- fic sites studied. Croft & AliNiazee (1983) later dis- covered low to moderate levels of resistance to organo- phosphate insecticides in T. arboreus as well as considerable populations of apparently resistant T. occidentalis in commercial orchards.
The objectives of this study were: 1) to identify 3 the phytoseiid species of major commercial crops of the Willamette Valley, 2) to assess inter-crop and seasonal distribution trends and the impact of insecticide sprays on the most abundant species found and 3) to identify the levels of resistance to pesticides in the most common phytoseiid species found. These objectives are relevant as pesticide usage on many crops in the valley is common and may increase with the recent introduction of new pests such as apple maggot (AliNiazee & Penrose, 1981) and gypsy moth (Anonymous, 1984b). Reducing the levels of acaricidal sprays via utilization of beneficial species in an IPM program would help growers maximize profits and reduce possibilities for resistance develop- ment in pest mites. 4
LITERATURE REVIEW Crop loss caused by insect pests is a constant threat faced by growers and pest control advisors world- wide. Pesticides are the primary control tactic used to avert excessive pest damage to most commodities. Heavy pesticide use has serious global implications concerning the creation of secondary pests, i.e.-those that cause indirect damage to the final commodity or are sporadic in occurrence (Luckman & Metcalf, 1982). Clancy & McAllister
(1958) and others documented resurgence of spider mites on deciduous fruit trees following applications of chlorinated-hydrocarbon and, later, organophosphate pesti- cides. Resulting high mite populations then caused severe leaf damage and losses in crop yield (Lienk et al., 1956; Croft, 1975b; Hoyt & Simpson, 1979).
Resistance to insecticides was a major factor in these secondary pest (especially mite) outbreaks (Brown,
1971; Georghiou, 1972). Economic and social pressures dictated that alternatives to insect control achieved solely by pesticides be found. The concept of IPM (as defined by Croft & Brown, 1975) was proposed as an im- provement to the unilateral pesticide strategy. One of the earliest attempts at IPM was in Nova Scotia apple orchards during World War II and is credited with saving that industry (Whalon & Croft, 1984).
Research and development of IPM programs were very 5 limited from the 1940s through the 1960s, as research was mostly oriented towards pest control by pesticides (Hoyt &
Burts, 1974). However, the past fifteen years has seen more development and implementation of IPM programs, especially control of spider mites by phytoseiids and selective pesticides. These IPM programs have evolved despite the doubts of some researchers, including Anderson
& Morgan (1958), Chant (1958,1959) and Zwick (1972).
Croft & McGroarty (1973,1977) and Croft (1975a) des- cribed the role of Amblyseius fallacis (Garman) in con- trolling tetranychid mites in commercial apple orchards of
Michigan. When selective sprays and conservative ground cover practices were used, A. fallacis usually kept Pan. ulmi, Tet. urticae and the eriophyid Aculus schlectendali
Nalepa at low levels. A. fallacis is important in IPM programs in the eastern and central U.S.A., being common in sprayed orchards in New York (Weires et al., 1979),
New Jersey (Knisley & Swift, 1972), Illinois (Meyer, 1974) and Missouri (Poe & Enns, 1969) as well as Michigan. 3stablishment of this species in New Zealand was reported by Cook (1982) . T. occidentalis is used to control Tet. mcdanieli and/or Tet. urticae on apple in Washington (Hoyt, 1969),
British Columbia (Madsen et al., 1975) and Australia
(Readshaw, 1975). Downing & Moilliet (1974) showed that the more arid climate of the western U.S. favored T. 6 occidentalis over an introduced species, A. fallacis, in commercial orchards. On other crops, T. occidentalis has been effective in controlling Tetranychus pacificus McGr. and Eotetranychus willamettei (McGr.) on grapes in
California (Flaherty & Huffaker, 1970; Kinn & Doutt,
1972), but was of questionable value in controlling spider mites on peaches in Australia (Field, 1976) and pears in
Oregon (Westigard, 1971). Huffaker & Flaherty (1966) con- sidered T. occidentalis to have potential for controlling
Tet. urticae on strawberry. Insecticide-resistant strains of T. occidentalis have been reared successfully in the laboratory and re-established in many areas of the world
(Readshaw, 1975; Croft, 1977; Penman et al., 1979).
Abroad, Typhlodromus pyri Scheuten has been used to control Pan. ulmi in commercial apple orchards in England
(Collyer, 1964; Easterbrook et al., 1979), Northern
Europe (Gruys, 1982) and New Zealand (Collyer & van
Geldermalsen, 1975; Collyer, 1976; Penman et al., 1979). Mathys (1958) found T. pyri important in limiting Pan. ulmi in Swiss vineyards. In the eastern U.S.A., Watve & Lienk (1975,1976) reported organophosphate and carbamate resistance in this species from strains collected in New
York apple orchards. While T. ari is occasionally found in the western U.S., it has usually been limited to non- sprayed orchards (Downing & Moilliet, 1972).
Phytoseiulus persimilis A.-H., an exotic phytoseiid 7 from Chile, has been used successfully to control Tet. urticae in greenhouses (Chant, 1961; Hussey & Scopes,
1977). Oatman et al.(1968) obtained a non-significant increase in yield of strawberries when 320,000 P. persimilis per acre were released in the field. On hops in Washington, Pruszynski & Cone (1972) found mass release of this species uneconomical due to heavy use of the organophosphate (OP) insecticide phosalone. P. persimilis has been established recently in some apple orchards in New Zealand where it aids in the control of
Tet. urticae (Cook, 1982). Research to find additional phytoseiids for IPM has included several other species. Croft et al.(1977) dis- cussed the use of native Amblyseius chilenensis (posse) in Uruguayan apple orchards. Pest mite control on apple in Chile using A. chilenensis has had some initial suc- cess (Gonzalez, 1981). AliNiazee (1979a,b) stated that
T. arboreus was a major factor in controlling Eotetranychus carpini borealis (Ewing) and Pan. ulmi in
Oregon apple orchards. Elbadry (1979) reported on the early season efficiency of Amblyseius gossipi Elbadry on cotton mite pests in Egypt. McMurtry (1982) provided an excellent summary of previous studies involving many other phytoseiid species. Many phytoseiid species can be unsuitable for use in
IPM programs. In Elbadry's work, although A. gossipi was 3 effective in early season, it was eliminated once the mid- summer insecticide sprays commenced. Croft & Jorgensen (1977) found Typhlodromus mcgregori Chant unable to con- trol Tet. urticae, Pan. ulmi or Bryobia rubrioculus
(Scheuten) on commercial apple in Utah and California.
In British Columbia (Downing & Moilliet, 1972) and
Wisconsin (Oatman, 1973), Typhlodromus caudiglans Schuster effectively regulated tetranychids in unsprayed orchards but was absent in commercial blocks. In still other cases, phytoseiids accepted as good IPM agents may display variable efficiencies (e.g.-T. pyri in a commercial pro- gram described by Wearing et al. (1978)).
In IPM programs, those phytoseiids that are proven most useful exhibit some or all of the characteristics considered necessary for an effective natural enemy
(Huffaker et al., 1970). One characteristic, environmen- tal synchrony, is extremely important in determining the success or failure of an IPM program utilizing an exotic phytoseiid. Croft & Nelson (1972) noted that the effectiveness of T. occidentalis was constrained by geo- graphical location in western North America. This species is limited to drier regions of the continent. Croft
(1982) reported it controlled Tet. urticae on various crops in the more arid parts of Australia while it was less effective in the more humid regions of that continent. Penman et al.(1979) had trouble establishing 9 an insecticide-resistant (R) strain of A. fallacis in New Zealand apple orchards because of high winter mortality.
This R-strain from Michigan, U.S.A. did not adapt well to the climate of New Zealand.
Two other characteristics of an effective natural enemy are predator-prey habitat synchronization and prey specificity. Chant (1959) realized the importance of having the predator and prey occupy the same microhabitat.
He considered this as one criterion to discount T. pyri as an effective biological control agent of Pan. ulmi in
England. However, McMurtry et al.(1970) believed this not essential (although helpful) and considered prey loca- tion on a leaf at any one time too static an observation to reflect a natural enemy's searching pattern. Chant (1958) also hypothesized that T. pyri's polyphagy would hinder its effectiveness as a control agent and extended this to include other phytoseiid species. This was com- pletely discounted by later research. Collyer (1964) found T. pyri provided better control of Pan. ulmi when the eriophyid Aculus fockeui Nalepa was available to T. pyri as an alternative food source. McMurtry & Scriven (1966) concluded that the effectiveness of Amblyseius hibisci (Chant) in controlling Oligonychus punicae (Hirst) was enhanced by the availability of fresh pollen as a food source. Hussey & Scopes (1977) noted that greenhouse populations of P. persimilis, a highly specific predator, 10 declined significantly due to a lack of an alternative food source after eliminating Tet. urticae from a green- house. The latter case illustrates one aspect of food limitation as it effects a natural enemy's survivorship
(Croft & Brown, 1975). This factor also influences development of resistance in both pest and beneficial species (Tabashnik & Croft, 1985). Therefore, the strict prey specificity of a natural enemy may be disadvantageous in some circumstances. Another characteristic important for successful bio- logical control is the ability of the natural enemy to control the prey species in a density-dependent fashion. While functional responses of phytoseiids to prey density have received only moderate attention (e.g.-Sandness & McMurtry, 1970), many researchers have investigated phyto- seiids' numerical response to prey density changes.
Anderson & Morgan (1958) and Chant (1958,1959) stated that phytoseiids have fewer generations, lower egg production and a higher winter mortality than their tetranychid prey, thus phytoseiids could never quickly respond to an in- creasing pest population. However, Huffaker & Flaherty
(1966) and Laing (1969) discovered that while Tet. urticae does have a higher fecundity than T. occidentalis, the actual intrinsic rate of increase of T. occidentalis is greater due to the species' more rapid development and reduction of gross prey fecundity by predatory action. 11 These data and accumulated evidence of successful IPM pro- grams for mites support phytoseiids' density-dependent response capabilities.
Huffaker et al.(1970) believed that searching capa- city is the most important characteristic regarding a predator's effectiveness in regulating prey. While many insectan predators have a much higher apparent searching capacity than phytoseiids, mites need far fewer prey to complete their development (Huffaker et al., 1970). This is significant in determining a predator's ability to regulate low densities of tetranychids. Early researchers
(Putman, 1962) hypothesized that spider mite predators located their prey principally by physical contact. Since phytoseiids have a low apparent search capacity, their effectiveness was questioned. Recent studies suggest that phytoseiids can detect local or relatively distant tetranychid populations via kairomones and other cues
(Hislop & Prokopy, 1981; Sabelis & van de Baan, 1983).
The final characteristic, and probably the most im- portant for establishing a phytoseiid as a biocontrol agent in a commercial crop ecosystem, is their potential for pesticide resistance development. Resistance has been much slower to develop in natural enemies than in pests
(Georghiou, 1972). Croft (1982) and Croft & Strickler
(1983) have published excellent reviews concerning this phenomenon among pest and beneficial species. 12
For phytoseiids, Smith et al.(1963) reported a tolerance to methoxychlor and DOT in A. fallacis and
Huffaker & Kennett (1953) noted a tolerance to parathion in T. occidentalis. The first documented case of resis- tance in phytoseiids was that by Motoyama et al. (1970) who found high levels of resistance to azinphosmethyl and parathion in A. fallacis and later hypothesized GSH
(Glutathione S-transferase enzyme) and non-specific esterases as the mechanisms involved (Motoyama et al.,
1971). Simultaneously, Croft & Jeppson (1970) documented azinphosmethyl resistance in T. occidentalis. Asquith et al.(1980) have stated that "...no other species is more intrinsically pesticide tolerant or resistance-adapted than T. occidentalis.". These two species have since shown a wide spectrum of resistance to chlorinated-hydro- carbon, organophosphate and carbamate compounds. Other phytoseiids with organophosphate or carbamate R-strains are: T. pyri (Hoyt, 1972 and others), A. chilenensis
(Croft et al., 1977), P. persimilis (Schulten et al., 1976), A. hibisci (Kennett, 1970), T. arboreus (Croft &
AliNiazee, 1983) and Amblyseius longispinosus (Evans) (Lo et al., 1984). Some phytoseiids found in highly sprayed regimes but not having documented resistance using sus- ceptible strains for comparison include Typhlodromus columbiensis Chant in British Columbia (Downing &
Moilliet, 1971), Amblyseius aberrans (Oude.) in Poland 13
(Dabrowski, 1970) and Amblyseius potentillae (Garman) in northern Italy (Ivancich-Gambaro, 1975). A. potentillae strains from elsewhere in Europe have been tested for organophosphate and carbamate resistance but no R-strains have been found (Overmeer & Von Zon, 1982; Kapetanakis &
Cranham, 1983). A. fallacis, T. occidentalis and T. pyri are the only species to presently exhibit resistance to synthetic pyrethroid (SP) compounds (Hoy et al., 1979; Croft et al., 1982; Strickler & Croft, 1982; Markwick,
1984). SPs are relatively new and are highly touted for their apparent low mammalian toxicity. Of all the resis- tant species listed, only A. fallacis, T. occidentalis, T. pyri, P. persimilis and A. chilenensis have been utilized extensively in IPM programs. Successful control of tetranychids in IPM is not limited to the use of phyto- seiids, e.g.-Stethorus punctum LeConte (Coleoptera: Coccinellidae) vs. Pan. ulmi in Pennsylvania apple or- chards (Hull et al., 1977). As evidenced, phytoseiid mites are important compo- nents in IPM programs for tetranychid mites worldwide.
Research continues to establish IPM programs utilizing phytoseiid predators in new areas and improve those already implemented (Whalon & Croft, 1984). 14
METHODS
Area and Crops Under Study
The cross-hatched area of Figure 1 represents the region of survey for phytoseiid mites on commercial crops of the Willamette Valley. The study was conducted during the growing seasons between August 1983-June 1985. The crops included in the survey were: (1)apple, (2)peach,
(3)pear, (4)prune-plum, (5)cherry, (6)filbert, (7)grape,
(8)strawberry, (9)raspberry, (10)blackberry, (11)corn,
(12)mint, (13)Christmas tree. All above crops are abundant throughout the valley and crops (1-10) were surveyed because they either have an extensive past history of IPM programs in North America or they are presently undergoing research for new IPM models. Corn is representative of a common annual crop. Mint has a well-documented history of problems associated with Tet. urticae (DeAngelis et al., 1983). Christmas trees were selected because of an apparent paucity of associated pest mite problems in the region.
Sampling and Classification Techniques Sample sites were chosen using county maps of local farms, obtaining information on crop locations from ex- tension or farm personnel and checking for additional sampling locations while enroute to pre-determined sites.
Every site's insecticide program was classified as 'low' if it received one insecticide application during the If I
ti
iis ...rs__I- ci
1 _., L._1.1 L/ ie 1 1
L._ i i
! ! , I i 1 i i., ! ! 1 ! i i I
ill I --) ! 0 i ! i ! 1 I i , ; ! i i i I V fl ...... 1 ; ; 1 .1 ; ; ; i i 1
Figure 1: Area of phytoseiid mite survey, including locations where T. pyri strains were collected for resistance testing (A). 16 growing season, 'moderate' if 2-3 sprays were used and
'high' if four or more treatments were applied. This in- formation was obtained by interviewing the grower. Table
1 lists the number of sites, by crop, in each spray cate- gory. Sites were sampled for mites several times during the growing season to measure seasonal differences. The seasonal periods for sampling were defined as: early
(20 March-10 June), mid (11 June-10 August) and late (11
August to the end of the year's sampling). Samples were composed of individual leaves collected randomly from vegetation and placed in 750m1 ZiplocRl brand freezer bags. Bags were completely filled to insure an equal volume of leaves was collected from each site and transported to the laboratory in an ice chest (ca. 7°C).
Samples for longer term storage were kept refrigerated at
4°C.
Phytoseiid mites were extracted from leaf samples using a Tullgren funnel with a 75-watt light bulb as a heat source (Schuster & Pritchard, 1963). A bean plant (Henderson Bush Lima variety) with low densities of Tet. urticae was placed in a jar of water that was attached to the bottom of the funnel. Leaves were held in the funnel for 24-48 hours. Ten leaves from each sample were band- checked before all leaves were deposited in the funnel.
1ZiplocR Brand Freezer Bags, Dow Chemical Company, Indianapolis, IN, 46268. 17
Table 1: Sampling sites inWillamette Valley, Oregon survey of phytoseiid mitesclassified by crop and spray intensity.
Crop Spray Regime Classification ILow1(1)1 'Moderate'(2-3) 'High'(4+) Apple (App) 22 11 22
Peach (Pch) 3 10 11
Pear (Per) 1 5 9
Prune (Prn) 12 5 4
Cherry (Chr) 13 11 8
Filbert (mt.) 1 14 10
Christmas tree (Xtr) 4 4
Grape 11 7
Blackberry (Bkb) 10 1 5
Raspberry (Rsb) 11 6 -
Strawberry (Stb) 14 16 3
Corn (Cm) 17 6
Mint (Mnt) 16 1
'Value in parentheses indicates number of insecticide applications crop received during growing season 2Value indicates number of sites in respective spray regime 13
The jar was tightly sealed to the funnel to prevent es- cape of trapped mites. After processing, bean plants were removed and phytoseiids transferred to Hoyer's mounting solution on a microscope slide. Mites were identified using Chant's (1965) taxonomic system.
Statistical Analysis Normality statistics, specifically multivariate
analysis, would have been most useful to assess the in-
fluence of key variables such as crop type, seasonal period and local insecticide programs on phytoseiid abun- dances. However, an assumption of normally distributed populations are necessary for these tests. In these experiments, this assumption could not be made. Zero and low number counts of mites were frequently observed in the samples, indicating a negative binomial-type distri- bution. However, individual samples containing large numbers of phytoseiids (15 or more mites) outnumbered samples where moderate quantities of mites (e.g.-6-10 phytoseiids) were collected. This significantly skewed the frequency distribution and subsequent data transforma- tion methods were inappropriate. The classification sys- tem of seasonal periods (i.e.-early, mid, late) and spray regimes (i.e.-low, moderate, high) is also not appropriate for parametric statistics. Therefore, the affect of the three above factors on the abundances of T. pyri, T. occidentalis and A. andersoni were measured individually 19
using nonparametric statistics. Seasonal differences in abundance were statistically compared using the Kruskal-
Wallis test (Lehmann, 1975). Data used were from sites sampled at least once during each seasonal period and in
which one or more individuals of the species in question
was collected. Inter-crop distribution of the three
species was also evaluated via the Kruskal-Wallis test.
The mean number of mites per sample per site was used in
comparing differences of mite abundance among crop types.
The Jonckheere-Terpstra statistic for ordered alternatives
(Lehmann, 1975) was used to examine the relationship be-
tween spray practices and abundances of phytoseiids, as
reflected in the mean number of mites per sample per site. Crops included in this test were those where greater than four percent of the total number of trapped individuals of
the species in question (across all crops) were found.
The classification of spray regimes was described earlier. T. pyri Resistance Test Techniques Colonies of T. pyri were established from areas
designated by triangles in Figure 1. Collection sites were chosen to emphasize extremes, i.e.-crops of low
pesticide pressure where mite populations would most likely be susceptible and crops receiving many pesticide
treatments, which would likely harbor resistant mites.
' Specific locations and related data for tested strains are
listed in Table 2. Mites were maintained and reared as 20
Table 2: Collection locations for five strains of T. pyri used in resistance tests.
SITE CROP SPRAY REGIME #IN.M.1
Corvallis, Benton Co. Blackberry Lowe 30 m3+ f4
Harrisburg, Linn Co. Grape Moderate 50 m + f
Forest Grove, Washington Co. Apple Low 28 m + f
Pleasant Hill, Lane Co. Apple High 50 m + f
Hood River, Hood River Co. Apple High 6 f
1NUmber of mites used to initiate laboratory colony 2See rating definition in Table 1 3Males 4Females 21 described by McMurtry & Scriven (1965). Predators were supplied with Tet. urticae daily and rearing arenas were changed when webbing became heavy. Levels of resistance of adult female mites to three insecticides, azinphosmethyl, carbaryl and parathion, were determined by a slide-dip technique (Busvine, 1980). Selection of insecticides was based on previous studies showing moderate to high levels of resistance to these compounds in T. pyri (Penman et al.,
1976; Overmeer & Von Zon, 1983; Kapetanakis & Cranham,
1983). Four concentrations of each compound were tested.
Four or five replicates of 20 mites per colony were evalu- ated at each concentration. Ten mites per dosage per colony (40-50 total mites) dipped in water were the con- trol. Each concentration of insecticide was tested at ca. seven day intervals due to limited source colony sizes.
Adult female mites were individually lifted off the colony with a fine, moist camel hair brush and placed on their backs on a piece of Permace1R2 brand heavy duty sticky tape. This tape was adhered to a standard 25x75mm micro- scope slide via double stickScotchR3 brand tape. Once 20 mites were secured to a slide, they were dipped in a 250m1 beaker containing 200m1 of the specific chemical concen- tration for five seconds. The beaker contained a magnetic
2Permace1R Brand Filament Tape, Dermacel Corp., New Brunswick, NJ, 08903. 3ScotchR Brand Double Stick Tape, 3M Co., St. Paul, MN, 55133. 22
stirrer to maintain a homogeneous mixture of the pesticide. Slides were then removed and tapped on a paper towel for one minute to eliminate excess moisture. Slides were transferred to a moist sponge on a standard cafeteria tray and covered by a clear plastic crisper, modified to allow
limited air circulation. This apparatus was then put into an environmental chamber with constant temperature (240C) and relative humidity (ca. 95%). Checks of mortality were made at 24 and 48 hours by gently prodding the mite on the hysterosoma or legs with a single-haired brush. Movement of any appendage, including the legs, palps or chelicerae indicated absence of mortality. Data were analyzed by the
PROBIT computer program (adapted from Mich. St. Univ. pro- gram) and LCP lines were constructed to estimate the extent of T. pyri's resistance levels to the chemicals tested. An
F-test for comparing regression lines (Weisberg, 1980) was used to check for significant differences between resistant or susceptible strains. 23
RESULTS
Species Distribution
A total of 1209 phytoseiids were collected from com- mercial crops of the Willamette Valley. Two genera, Amblyseius Berlese and Typhlodromus Scheuten were repre- sented by seven and four species, respectively. Figure 2 shows the distribution of species among crops and Appendix
1 provides the numerical totals. Twelve protonymphs were unidentifiable and were omitted from the data in Figure 2 as were species whose relative abundance was less than one percent of the specific crop's phytoseiid fauna. A group of similar Amblyseius species were combined into a single category in Figure 2 to facilitate data presenta- tion.
T. pyri was the most abundant phytoseiid collected from Willamette Valley commercial crops, representing 51% of the surveyed mites, outnumbering the second most abun- dant phytoseiid, T. occidentalis, almost three-fold. T. pyri was collected from 10 of 13 crops, ranging from pros- trate plants such as strawberry to arboreal plants such as apple (Figure 3) .
T. occidentalis accounted for 17.5% of the surveyed phytoseiids and was widely distributed between crops, al- though this species was more numerically prevalent in apple and cherry (Figures 2 & 4).
Amblyseius andersoni (Chant) was found on all sampled 4 AJ ...... anno...... MMMMM ...... 11MNVONNIM '..:MLABEIWAIM 000 I ' . .; I I MOO . I
4 a 25
a= apple b= blackberry c= cherry e= pear f= filbert g= grape k= corn m= mint p= peach r= raspberry s= strawberry u= prune x= Christmas tree
Figures 3-10: Collectionlocations in Willamette Valley, Oregon, by crop, of phyto- seiids (Legend; symbols designate crop type). 26
Figure 3: Collection locations inWillamette Valley, Oregon, by crop, of T. pyri. 27
- - - - -1 J 1_ f i 'I I -1-1.1.u. t1, rII It rV. 1 r 1 1_ I ..,-- I 1, 0 1 1 il et_ !
I I 1 rI I l11 L.... III \ - N I \ l RI Ia i \ aa I 4 i C 0
1
a
Figure 4: Collection locations inWillamette Valley, Oregon, by crop, of T.occidentalis. 28 crops except filbert and represented 9.8% of the collected specimens. This species tended to occur more frequently on vine crops than arboreal habitats (Figures 2& 5). Almost 99% of A. aberrans were recovered from fil- bert, with single specimens also collected from apple and prune (Figures 2 & 6). This species comprised 13.3% of the total sampled phytoseiid population.
T. arboreus represented just over four percent of the phytoseiids found. This species was locally common on apple and prune (Figures 2 & 7). However, this species was not as widespread in commercial apple orchards as reported by AliNiazee (1979a).
A. fallacis was found almost exclusively on straw- berry and corn (Figures 2 & 8) and usually occurred in small numbers. This species was only 2.5% of the entire sampled phytoseiid fauna.
The only specimen of Typhiodromus rhenanoides A.-H. was recovered from an incidental sample of moss from filbert (Figure 9).
The Amblyseius 'complex' consisted of Amblyseius brevispinus (Kennett), Amblyseius reticulatus (Oude.), Amblyseius umbraticus (Chant) and Amblyseius zwoelferi
(Dosse). The three latter species were found only on strawberry while A. brevispinus was also collected from corn (Figures 2 & 10). This 'complex' was represented by only eight specimens. 29
Figure 5: Collection locations in Willamette Valley, Oregon, by crop, of A. andersoni 30
r
1
_ _ i
Figure 6: Collection locations in Willamette Valley, Oregon, by crop, of A. aberrans. 31
r
Figure 7: Collection locations in Willamette Valley, Oregon, by crop, of T. arboreus. 32
Figure 8: Collection locations in Willamette Valley, Oregon, by crop, of A. fallacis. 33
Figure 9: Collection locations in Willamette Valley, Oregon, by crop, of T. rhenanoides. 34
Figure 10: Collection locations in Willamette Valley, Oregon, by crop+ of Amblyseius 'complex'. 35 A dichotomous key and accompanying figures for the identification of phytoseiid mites of commercial crops in the Willamette Valley as represented in this study is presented in Appendix 2.
Tables 3-5 show the results of tests analyzing the distribution between crops of T. pyri, T. occidentalis and
A. andersoni, respectively. Table 3 shows that T. pyri occurred at significantly higher levels (P=0.05) in apple, prune, grape and blackberry than in other crops. All crops where at least one T. pyri was recovered (except the four crops just mentioned) yielded nonsignificant differences.
Table 4 indicates that T. occidentalis was more pre- valent on apple than on all other crops except cherry.
All crops where T. occidentalis was collected at least once (except apple and cherry) yielded a nonsignificant
K-value. When apple alone was tested with these nine crops, a significant K-value was obtained. When only cherry was tested with the nine crops, the result was a nonsignificant K-value. However, a nonsignificant K-value was recorded when apple was tested against cherry.
A. andersoni was significantly more abundant in rasp- berry, blackberry and Christmas trees (Table 5) than in other sampled crops. A. andersoni was collected in low numbers from deciduous fruit trees. Some crops such as grape, corn and cherry yielded nonsignificant K-values Table 3: Results of Kruskal-Wallistests checking forsignificant differencesin abundance betweencrops ofT. pyri.
Crops Tested do K2 Probability Level
Apple(144)3,Peach(16),PeAr(6), Prune(115),Cherry(32),Grape(144), Blackberry(117),Raspberry(31), Strawberry(8),Corn(0),Mint(0), Filbert(3),X-mas tree(0) 12 92.55* P(K>92.55)<0.0005
Apple,Peach,Pear,Prune,Cherry 4 14.80* 0.01O
Peach,Pear,Cherry 2 0.05908 0.950
Apple,Prune 1 0.5785 0.30
Grape,Blackberry,Raspberry 2 10.04* 0.005
Grape,Blackberry 1 0.1214 0.70
Apple,Prune,Grape,Blackberry 3 6.018 0.10
Peach,Pear,Cherry,Filbert, Raspberry,Strawberry 5 10.03 0.05
1Degrees of freedom 2Kruskal-Wallis value 3Values in parentheses indicate total numbers of T. pyri collectedon specific crop *Significant at P=0.05 level Table 4: Results of Kruskal-Wallistests checking forsignificant differencesin abundance betweencrops ofT. occidentalis.
Crops Tested df K Probability Level
Apple(83),Peach(8),Pear(20), Prune(10),Cherry(63),Grape(4), Blackberry(5),Raspberry(7), Strawberry(3),Corn(1),Mint(6), Filbert(2),X-mas tree(0) 12 30.88* 0.001
1Series A represents crops: Peach, Pear, Prune, Grape, Corn, Blackberry,Raspberry ,Mint, Strawberry Table 5: Results of Kruskal-Wallistestscheckingfor significant differencesin abundance betweencrops of A.andersoni.
Crops Tested df K Probability Level Apple(7),Peach(1),Pear(2), Prune(1),Cherry(22),Grape(3), Blackberry(19),Raspberry(33), Strawberry(8),Corn(10),Mint(1), Fiibert(0),X-Imas tree (11) 12 47.50* P(K>47. 50)<0.0005 Apple, Peach, Pear, Prune, Cherry 4 8.603 0.05
grape vs. blackberry, cherry vs. Christmas trees). How- ever, grape, corn and cherry also gave nonsignificant K- values when compared to crops where very few A. andersoni were collected. Some of these crops may be regarded as harboring significant populations of A. andersoni, but in numbers somewhat lower than those of raspberry, blackberry and Christmas trees (see Appendix 1).
The temporal trends of phytoseiids during the growing season in the Willamette Valley by crop are shown in Figure 11. T. pyri showed no significant difference in its abundance during different times of the growingseason (Table 6). The raw data of Appendix 3 show no real pat- tern concerning absolute numbers of T. pyri. However, Figure 11(a,c,e,f,g) shows that T. pyri had a higher relative abundance in apple, pear, cherry, grape and blackberry during the early season. Apple, grape and blackberry are among the four crops previously shown to have significantly higher levels of T. pyri. T. pyri was also found in the same abundances in early and mid season on peach and had higher absolute numbers on prune in early season than at other times (Figure ll;b,d). Overall, while the statistics showed no significant seasonal dif- ferences for T. pyri, the data indicate that this species was more abundant in early season on many commercial crops than other phytoseiid species. On crops such as prune, 40
10= T. pyri
0= T. occidentalis
um L.= A. andersoni
= A. aberrans
111= T. arboreus
0= A. fallacis
El= A. 'complex'
Figure 11: Distribution of phytoseiids during growing season on commercial crops of the Willamette Valley, Oregon (Legend). n=93 79 102 1.0
0.75
0.50
0.25 0w 2 Q ca2 m a. apple I. peach
>W P n= 4 4 20 70 38 28 scc 1.0 W cc 0.75
EARLY MID LATE EARLY MID LATE teem d. prase SEASONAL PERIOD Figure 11: Distribution of phytoseiids during growing season on commercial crops of the Willamette Valley, Oregon. n= 21 29 67 51 77 23 1.0
0.75
0.50
0.25 W C.) 4z Oz m e. cherry I. grape
W> P n= 45 60 37 18 24 29 4 1.0 ...1 W m 035
EARLY MID LATE EARLY MID LATE g. blackberry h. MOW, SEASONAL PERIOD Figure 11: Seasonal distribution of phytoseiids, cont'd. n= 23 13 11 1 10 1.0
0.75
0.50
0.25 ILJ zU 4 0 z m i. strawberry 4 w n.-- 7 417 LO w...1
0.75
EARLY MID k, mint SEASONAL PERIOD
Figure 11: Seasonal distribution of phytoseiids, cont'd. 11
1035 = <0.50 11 0.25
cc
UM/ NW LATE 111.016sWastru SEASONAL PERIOD
Figure 11: Seasonal distribution of phytoseiids, cont'd. Table 6:Assessment of temporal trends of phytoseiidspeciesT. pyri, T. occidentalis and A. andersoni on WillametteValleycrops, based on Kruskal-Wallis tests.
Species Seasons Tested df Probability Level T. pyri Early(248)1,Mid(230),Late(138) 2 1.040 0.50
1.040)<0.60 Early,Mid 1 0.7449 0.30
T. occidentalis Early(18),Mid(68),Late(126) 2 14.86* 0.0005
Mid, Late 1 0.2853 0.50
A. andersoni Early(21),Mid(43),Late(54) 2 1.066 0.50
Mid, Late 1 0.02832 0.80
1Values in parentheses indicate total numbers of species collected during specific seasonal period *Significant at P=0.05 level 46 grape and blackberry, T. pyri remained the most abundant species throughout the growing season. T. occidentalis was significantly less abundant during early season than at mid or late season (Table 6).
Its relative abundance on apple, peach, prune, cherry and blackberry increased as the season progressed (Figure 11; a,b,d,e,g) and in raspberry and strawberry, it appeared only during mid season (Figure ll;h,i).
A. andersoni exhibited no significant seasonal dis- tribution (Table 6). On some crops (e.g.-apple, grape), its relative abundance increased as the season progressed
(Figure ll;a,f), but this trend was not consistent. Among the minor species not statistically tested, no patterns were evident except for the Amblyseius 'complex', which appeared only during early and late season on straw- berry and corn (Figure 11;i,j).
The distribution in relation to spray regime of phytoseiids collected by crop is shown in Figure 12. Numerical totals are provided in Appendix 4. T. pyri was significantly more abundant in crops receiving fewer in- secticide treatments (Table 7), usually appearing in lower numbers as the crop was more intensively sprayed with insecticides. T. occidentalis did not exhibit a statistically significant pattern of being most abundant in crops receiving high numbers of insecticide sprays and in progressively lower quantities as less treatments were 47
= T. pyri
= T. occidentalis
m; ME= A. andersoni
= A. aberrans
= T. arLoreus
= A. fallacis
= A.'complex'
Figure 12: Distribution between spray regimes of phytoseiids collected on Willamette Valley, Oregon commercial crops (Legend) . n= 23 115 136 2 16 7
0w0.25 Z 0< Z m a. apple hdmach 4m W > n= P 4 24 110 20 6 _ia 1.0 W
0.75
0.50
0.25
...... i ..... LOW MOO LOW MOO HIGH c. pear SPRAY REGIME d. prune
Table 12: Distribution between spray regimes of phytoseiids collected on Willamette Valley, Oregon commercial crops. n= 44 19 54 88 63
0.25 z0 .4 z0 m s. cherry I. 1r ape 4m >w n=122 19 i= 1 43 28 _,a to w m 0.75-.
0.50
0.25
LOw MOO HIGH LOW MOO HIGH g. blackberry SPRAY REGIME b. raspberry
Figure 12: Spray regime distribution of phytoseiids, cont'd. n= 17 25 5 15 1.0
0.75
0.50
0.25 W 2 2O i. strawberry 4 j. um
P n= 7 19 113 34 41.0
0.75
0.50
0.25
LOW MOO HIGH LOW MOO HIGH k. mint SPRAY REGIME Haut
Figure 12: Spray regime distribution of phytoseiids, cont'd. 3 8
04 0.75 0z OW III. CkristMas tree SPRAY REGIME Figure 12: Spray regime distribution of phytoseiids, cont'd. Table 7: Assessmentof impact of spray regime on abundanceof phytoseiid species T. pyri,T. occidentalis and A. andersoni on WillametteValley crops, based on Jonckheere-Terpstra tests. Species Tested H2 J3 z4 Probability Level H 01 a (346)5 (174) (96) T. pyri 2.857 P(z>2.857)=0.0021 ubaelMODHIGH uHIGH<1114DD (33)(53) (126) T. occidentalis 2790 0.638 P(z>0.638)=0.2611 uLOW=u1CIPIIIIIGH uLow (71)(43) (4) A. andersoni 5102 2.209 P(z>2.209)=0.0136 ull3WMOD=11HIGH uHIGH 1Null Hypothesis 2Alternate Hypothesis 3Jonckheere-Terpstra value 4z-approximation 5Values in parentheses above spray regimes of Ho indicate total number of individuals of respective species collected at corresponding spray regime 53 applied (Table 7). However, on deciduous fruit trees, where T. occidentalis was most often collected, its ab- solute and relative abundances in low and moderatespray regimes were much less than those in highly treatedareas (Figure 12;a,b,c,d,e). A. andersoni's distribution be- tween spray regimes was consistent with the alternate hypothesis of Table 7, being most abundant in sites of low insecticide treatment and present in lower numbersas the quantity of insecticide applications increased. This trend can be seen in almost all crops (Figure 12). Among the remaining species, A. fallacis was most prevalent on strawberry and corn crops receivinga moderate level of insecticide treatment (Figure 12;i,j). The few specimens of the Amblyseius 'complex' collected from strawberry and corn were from the low spray regimes (Figure 12;i,j). T. arboreus was absent from low sprayed apple orchards but locally common in some orchardsre- ceiving a moderate level of insecticide applications (Figure 12;a). This may be due to the small number of low spray apple orchards sampled. T. arboreus exhibited a similar pattern on prune (Figure 12;d). Insecticide Resistance in T. pyri Since T. pyri was the principal phytoseiid found in this study, it was important to obtain baseline resistance levels to some commonly-used insecticides for these populations. T. occidentalis, A. andersoni and T. 54 arboreus from Willamette Valley sites have already been tested by Croft & AliNiazee (1983) but no such tests have been conducted on Willamette Valley T. pyri strains. Table 8 shows the results of slide-dip tests using azinphosmethyl. Figure 13 provides the LCP lines of the five strains of T. pyri. The R- strains, Hood River, Pleasant Hill and Harrisburg, all had 48-hour LC50 values higher than the upper limit of the recommended field rate (600ppm) and were 5-7 fold more resistant than the two S-strains. The S-strains from Corvallis and Forest Grove both had LC50values well below the lowest recommended field rate (300ppm). The azinphosmethyl R-strains exhibited high levels of resistance to carbaryl (Table 9& Figure 14). The 48-hour carbaryl LC50 values for the R-strains were well above the maximum field rate (ca. 1100ppm) and exhibited 25-27 fold resistance to carbaryl when compared to the S-strains. The 48-hour carbaryl LC50 values for the S-strains dif- fered. The value of the Forest Grove strain was near the lower field rate (600ppm) while the Corvallis strain's LC50 was closer to the higher recommended rate (1100ppm) of carbaryl. Comparing the LCP lines of similar S- and R-strains (Table 10) showed no significant difference between S- strains for azinphosmethyl or carbaryl and no significant difference between R-strains for both chemicals. Table 8: Susceptibilityof T.pyri collectedfrom different locationsin Oregon to azinphosmethyl. Nbrtality LC (plan) Colony Source Check (hrs) 50 95%C. I . (ppm) 1 Slope R2 Fold -R2 Corvallis* 24 188 180-197 2.454 0.98 48 128 122-134 2.391 0.97 Forest Grove* 24 236 229-244 2.940 0.95 48 150 147-154 3.234 0.97 Harrisburg* 24 1385 1306-1469 2.515 0.96 7.37 48 733 704-762 2.880 0.94 5.73 Pleasant Hill* 24 1082 1042-1123 3.143 0.92 5.76 48 618 602-634 3.409 0.90 4.83 Hood Rivert 24 1626 1510-1751 2.159 0.97 8.65 48 911 857-968 2.351 0.94 7.12 195% confidence interval 2LC R-strain/LC S-strain 50 50 *Willamette Valley tHood River Valley Table 9: Susceptibilityof T.pyri collectedfrom different locations in Oregon to carbaryl. Mortality LC (ppm) 2 Colony Source Check (hrs) 50 95%C.I.(ppm) Slope R Fold -R Corvallis 24 1986 1880-2098 1.209 0.98 - 48 1081 1047-1117 1.472 0.99 Forest Grove 24 2979 2414-3675 0.517 0.69 48 796 731-866 0.867 0.91 Harrisburg 24 39186 33163-46303 2.639 0.94 19.73 48 21760 21015-22531 3.887 0.99 27.34 Pleasant Hill 24 29158 27386-31044 3.647 0.99 14.68 48 19875 19452-20308 4.482 0.98 24.97 Hood River 24 30549 27989-33344 3.212 0.87 15.38 48 20136 19621-20664 4.199 0.98 25.30 *--*FOREST GROVE a--0 CORVALLIS PLEASANT HILL 0 0 HARRISBURG *--*HOOD RIVER F>- M ccl 50 * 0 2 aQ 10 FIELD RATE 100 1000 10000 100000 CONCENTRATION (PPM) Figure 14: Carbaryl 48-hour lethal concentration response curves of strains of T. pyri occurring in Willamette Valley, OR and Hood River, OR. Table 10: F-test for comparison of similar LCP lines of T. pyri collected from different locations in Oregon. AZINPHOSMETHYL Tested Strains F-value Probability Level Corvallis, Forest Grove 0.1379 P(F>0.1379)<0.50 Harrisburg, Pleasant Hill, Hood River 0.1859 P(F50.1859)<0.50 CARBARYL Tested Strains F-value Probability Level Corvallis, Forest Grove 0.1277 P(F50.1277)<0.50 Harrisburg, Pleasant Hill, Hood River 1.510 0.10 The slide-dip tests with parathion were harder to interpret. Figure 15 gives the data obtained from the tests. For the R-strains, mortality decreased when high concentrations of parathion were used, yielding unreliable LC50 values (Table 11). Repetition of the higher concen- trations on the R-strains gave similar results. Using lower rates of parathion to evaluate resistance in S- strains gave more interpretable results (Table 11). The most reliable data for a R-strain indicated a 200-fold resistance to parathion at a 48-hour mortality check. * 0 .. .., * ,,, .*--- o I ..?". * 10 *-* FOREST GROVE 0--a CORVALLIS - PLEASANT HILL O O HARRISBURG 0- -it HOOD RIVER 10 0 100 1000 10000 CONCENTRATION (PPM) Figure 15: Parathion 48-hour lethal responsORe curvands of strainsofT. pyri occurring in Willamette Valley, River,OR. Table 11:Susceptibility of T.pyri collectedfrom differentlocations in Oregon to parathion. Mortality (ppm) 2 Colony Source Check airs) X50() 95%C.I.(ppm) Slope R Fold -R Corvallis 24 39 36-42 1.698 0.82 48 17 16-18 1.947 0.73 Forest Grove 24 38 35-43 1.394 0.73 48 19 18-20 1.789 0.78 Harrisburg 24 3971 3698-4264 1.493 0.81 104.50 48 3378 3175-3593 1.647 0.70 198.71 Pleasant Hill 24 0.36 48 0.15 Hood River 24 4450 3992-4961 1.208 0.67 117.11 48 4614 3934-5411 0.946 0.44 271.41 63 DISCUSSION Typhlodromus pyri T. pyri's apparent absence from earlier surveys of commercial apple orchards in the Willamette Valley was probably due to local dominance of T. arboreus in the specific orchards sampled and misidentification of some collected specimens (Hadam, unpublished records). In this study, T. pyri was most abundant in apple, prune, grape and blackberry. The impact of spray prac- tices seemed to be a major factor in T. pyri's abundance on certain crops. For example, prune and most vine crops do not receive intensive insecticide applications as do crops such as apple and pear. T. pyri in the Willamette Valley was most abundant in these low sprayed crops, which commonly harbor eriophyid and tydeid mites as well as tetranychids. In contrast to prune and vine crops, apple orchards in the Willamette Valley often receive five or more insecticide applications per year, yet T. pyri was often abundant on this crop. T. pyri's presence in some highly treated apple orchards throughout the year and subsequent results of the slide-dip tests indicated that significant levels of resistance have developed in T. pyri on certain crops in the valley. The slide-dip tests also indicated that development of resistance in T. pyri in the valley is a local phenomenon rather than a regional occurrence and depends on the past history of pesticide 64 use at individual sites. In addition to resistance development, survival of T. pyri in apple orchards may be high due, in part, to its preference for sheltered micro- habitats (e.g.-within buds and emerging leaf clusters) very early in the season when insecticide applications are initiated (Niemczyk, 1965). Some Willamette Valley cherry orchards received low numbers of insecticide treatments and harbored a diversity of acarine pests, yet T. pyri was usually absent or in very low abundances on this crop. T. pyri is very sus- ceptible to dimethoate (Watve & Lienk, 1975; Wearing, pers. com.), an insecticide commonly used on cherry in the early season throughout the valley. Only one third of T. pyri collected on cherry in the survey was re- covered during early season, when most dimethoate sprays were applied. The impact of sprays may not be the only factor determining the presence or absence of T. pyri on Willamette Valley crops. Pear and peach should also har- bor local resistant strains of T. pyri if spray programs were the sole controlling variable. Raspberry represented a low sprayed vine crop that had low T. pyri levels throughout the valley in comparison to blackberry and grape. Pear, peach and raspberry, along with cherry, filbert and corn, usually lack pubescence on the leaf's ventral surface. Among phytoseiids, Phytoseius macropilis 65 (Banks) and T. caudiglans seem to prefer plant species and/or varieties that have highly pubescent leaves and pronounced veins (Collyer, 1958; Downing & Moilliet, 1967). This may also be the case for T. pyri, which was often observed in close proximity to the central rib and larger subsidiary veins of leaves. Lack of leaf pubescence, along with a lack of preferred food types on pear, peach, cherry, raspberry, filbert and corn, may partly account for T. pyri's low abundance on these crops. Fungicides were not considered in the analysis of spray regimes. Many researchers have documented fungi- cides' detrimental effects on phytoseiid mites (MacPhee & Sanford, 1954; Collyer & Kirby, 1955; Gruys, 1982). Specifically, T. pyri is adversely affected by some fungicides used in New Zealand apple orchards (Wearing & Proffitt, 1983). Peach orchards in the valley are often subject to intense fungicide programs and whether fungi- cides are a factor affecting T. pyri's abundance on some Willamette Valley crops remains unknown. There were no statistically significant trends in T. pyri's abundance during different growing season periods but there were less individuals collected late in the season than in other periods. T. pyri is associated with more humid, moist climates (Collyer, 1976), similar to that of the Willamette Valley early in the growing season. During late July through September, however, the valley 66 assumes a more hot, arid climate that would tend not to favor T. pyri. This "arid" environment may favor develop- ment of T. occidentalis populations (Croft, 1982). This less favorable climate for T. pyri along with, in some in- stances, competition from T. occidentalis may help explain T. pyri's decline late in the season. Pan. ulmi, a major prey species of T. pyri in commercial crops, also declines in abundance late in the season and is replaced by Tetranychus spp. or Eotetranychus spp. (AliNiazee, 1979a; Penman et al., 1976). T. pyri, however, can use alter- native food sources to balance the decline in Pan. ulmi, so a lack of 'preferred' prey late in the seasonshould not have been a factor in its lower late season abundance in the deciduous fruit trees. A lack of 'acceptable' prey may be responsible for T. pyri's low numbersin strawberry, which had a different acarine pest complex than most other crops studied (Tet. urticae being the major pest alongwith the tydeid Stenotarsonemus pallidus (Banks)). The resistance tests of T. pyri strains to azinphos- methyl gave similar results to those found by Hoyt (1972), Watve & Lienk (1976) and Kapetanakis & Cranham (1983). Overmeer & Von Zon (1983) obtained much lower LC50 values for their R-strain (1.8ppm) but used a glass-residue method and made mortality checks at 96 hours. The long period before mortality counts may have been partly res- ponsible for the low LC50 values. After exposure to 10-15 67 years of intensive azinphosmethyl treatments, strains of T. pyri in New Zealand with azinphosmethyl LC50s of 3000 ppm (24 hour mortality check) were reported by Penman et al.(1976). Levels in this study's R-strains are lower, possibly reflecting the lower number of yearly insecticide applications used in the valley and the greater popularity of phosmet over azinphosmethyl among growers in the region. Resistance to azinphosmethyl is much lower in T. pyri R-strains than A. fallacis and T. occidentalis R- strains. The two latter species have 100-1000 fold re- sistances to this compound when compared to S-strains (Motoyama et al., 1970; Croft & Jeppson, 1970). Resistance of T. pyri in the Willamette Valley to carbaryl parallels that found by Watve & Lienk (1976) in New York and Kapetanakis & Cranham (1983) in England. LC50s to carbaryl were higher than those reported in the literature for A. fallacis and T. occidentalis (Croft & Meyer, 1973; Roush & Hoy, 1981). The high LC50s of T. pyri S-strains from the valley may indicate an inherent tolerance to carbaryl with subsequent higher levels at- tained through resistance development. Other researchers have hypothesized that T. pyri has a natural tolerance to carbaryl (van de Vrie, 1967; Croft, 1981). The flat slopes for carbaryl of the S-strains obtained in this study suggest a high variability for carbaryl tolerance within T. pyri populations. 68 The parathion tests of this study should be viewed with some caution. Repeated trials of the higher concen- trations frequently gave equal or lower mortality than some lower dosages (except in the Harrisburg strain). This effect was most likely due to an inability to obtain higher amounts of compound in solution when using an emulsifiable concentrate formulation. The Harrisburg R-strain was over two orders of magni- tude more resistant to parathion than the S-strains. The LC50 for the R-strain was higher than that observed by Kapetanakis & Cranham (1983) and Overmeer & Von Zon (1983), but the high fold-R level (LC50 R-strain/LC50 S- strain) was consistent with previous findings. The relatively flat slopes of the LCP lines for S-strains once again indicate some variability within the populations. van de Baan et al.(1985) used paraoxon (the active form of parathion) to isolate the mechanism of resistance in T. pyri. They found insensitivity of acetylcholin- esterase (AChE) in an R-strain of T. pyri responsible for resistance to paraoxon and propoxur. This resistance mechanism would account for the discrepancies between azinphosmethyl and carbaryl resistance, the apparent cross-resistance between carbaryl and parathion and the differences in overall resistance between T. pyri and the other widely-studied species, A. fallacis and T. occidentalis. Dephosphorylation is negligible in AChE 69 inhibition, resulting in low resistance levels in T. pyri to OPs such as azinphosmethyl. Decarbamylation, however, occurs at a much higher rate with thismechanism, result- ing in low susceptibility to carbamate insecticides such as carbaryl. In contrast, A. fallacis detoxifies OPs quickly via high activity of glutathione S-transferase and non-specific esterases (Motoyama et al., 1971), re- sulting in high resistance to many OPs. Intensive selection was required, however, to achieve moderate carbaryl resistance in A. fallacis (Croft & Meyer, 1973). The results of this study agreed with the literature data, i.e.-high resistance of T. pyri to carbaryl and lower levels to azinphosmethyl along with 100-200 fold resis- tance to parathion, and supported the hypothesis that in- sensitive AChE is the resistance mechanism of R-strains of T. pyri in the Willamette Valley and Hood River. The results of the F-tests between similar LCP lines may reflect that resistance to azinphosmethyl and carbaryl of T. pyri in the region has reached an upper plateau under current spray practices. Barring future occurrences of cross-resistance to other compounds, management pro- grams based on conservation of R-strains of this species may need to keep this conclusion in mind. There is question whether T. pyri of the Willamette Valley is conspecific with T. pyri from other parts of the world. Other phytoseiids have been split into sibling 70 species as a result of cross-breeding studies. Mahr (1978), for example, found T. arboreus from the Willamette Valley incapable of cross-breeding with some morphological- ly identical populations in California he later described as Typhlodromus johnsoni Mahr. These species were separated by minute setal length and spermathecal dif- ferences. Congdon & McMurtry (1985) reported similar re- sults for A. hibisci. T. pyri from the Willamette Valley vary from those collected in Canada by Chant etal.(1974) by having three pairs of pores on the dorsal shield instead of four but are similar to T. pyri recovered by Schuster & Pritchard (1963) in California. T. pyri from the valley was reared more successfully on Tet. urticae than T. pyri from other areas (Watve & Lienk, 1975; Croft, pers. com.). Whether T. pyri is a complex of nearly identical species needs to be resolved by cross-breeding experiments. Typhlodromus occidentalis T. occidentalis of the Willamette Valley showed much morphological variation of the ventrianal shield. Dis- figurations of the shield and extra setae were not uncommon in this species and were consistent within populations from individual orchards. Davis (1970) also noted morphological variations in T. occidentalis between orchards in Utah. T. occidentalis was found predominantly on apple and cherry in the Willamette Valley, usually in moderately or highly sprayed orchards late in the season. This species 71 prefers arid climates and is less adapted to humid regions (Croft, 1982) which may explain its low abundance in the valley during early season. As the hotter and drier weather typically commenced in mid to late season and the cumulative number of insecticide applications eliminated more susceptible competing species, T. occidentalis became more prevalent. The Jonckheere-Terpstra test did not support the hypothesis of uLow Tet. urticae on peach in Australia. Pan. ulmi, however, is the principal acarine pest on peach in the Willamette Valley. T. occidentalis is not an efficient predator of Pan. ulmi and therefore may not be prevalent on peach be- cause of a lack of preferred food source. Low levels of T. occidentalis on highly sprayed pear are hard to explain. Some orchards had moderate populations of Tetranychus sp. or Eotetranychus sp., which are usually favorable food 72 sources for T. occidentalis. Use of chemicals not favor- able to T. occidentalis could be the principal reason for the species' low abundance on pear (e.g.-synthetic pyrethroids, amitraz). On grape, blackberry, raspberry and strawberry in the valley, T. occidentalis was rare, despite being widely collected on these commercial crops in California (Huffaker & Flaherty, 1966; Kinn & Doutt, 1972). In most cases, insecticides are more intensively used on these crops in California than in the Willamette Valley. This could result in higher faunal diversity in these Willamette Valley crops, which may put the relatively prey-specific T. occidentalis at a competitive disadvan- tage to other generalist species (Kinn & Doutt, 1972). T. occidentalis was the most prevalent species col- lected in mint (6 of 7 specimens). Hollingsworth (1980) reportedly found A. fallacis and A. brevispinus on mint in eastern Oregon. These observations are puzzling since the arid climate of eastern Oregon would seemingly favor T. occidentalis, not A. fallacis. While mint in the valley is often a low sprayed crop, moderate to high populations of Tet. urticae, a preferred food of T. occidentalis, were commonly observed in the field. Cultural practices (e.g. - flaming) make mint a disturbed habitat and may not allow time enough for T. occidentalis to disperse into the field and become established before the crop is harvested 73 (Hollingsworth, 1980). As T. occidentalis is considered a 'resistance- adapted' species (Asquith et al., 1980), it has great potential for use in future IPM programs in the Willamette Valley. Amblyseius andersoni Like T. pyri, the distribution of A. andersoni was strongly influenced by local insecticide programs. (This was evidenced in both the Jonckheere-Terpstra testfor the impact of spray practices and the inter-crop distribution Kruskal-Wallis test.) A. andersoni was rarely collected from deciduous fruit trees, including prune which is normally a low sprayed crop. The higher number collected from cherry was due to a single sample from a low sprayed orchard. A. andersoni was more abundant than T. occidentalis in the vine crops, which usually receive a low-intensity insecticide program. A. andersoni was often collected on wild blackberry, wild strawberry and wild hazelnut during the study period (Hadam, unpublished records). The wide spectrum of host plants of A. andersoni, both commercial and wild, indicates this species is probably a generalist feeder and can utilize a diversity of food resources. A fairly large pool of A. andersoni on wild host plants probably explains its seasonal abundances on many commercial crops. This would allow for dispersal from wild plants to neighboring com- 74 mercial plots between infrequent insecticide applications. A. andersoni was the only species collected from Christmas trees. This may reflect the inadequacy of the extraction method on this crop rather than a lack of phytoseiid diversity (Charlet & McMurtry, 1977). Samples from Christmas trees often remained in the Tullgren funnel for over four days in order for the vegetation to lose moisture. This species may be an important regulator of acarine pests in very low sprayed and organically-grown crops in the valley. Several strains of A. andersoni previously collected in the Willamette Valley were very susceptible to azinphosmethyl, diazinon, carbaryl and phosalone (Croft & AliNiazee, 1983). A very similar, and possibly con- specific species (McMurtry, 1977) in Europe, A. potentillae, is considered an important predator of Pan. ulmi under low spray conditions (van de Vrie & Boersma, 1970). A. potentillae has, however, been observed in moderately sprayed peach orchards in Italy (Ivancich- Gambaro, 1975). Further resistance tests and feeding studies will help assess A. andersoni's potential in IPM programs on Willamette Valley commercial crops. Amblyseius aberrans A. aberrans' exclusive presence on filbert is ex- plained by its association with its prey, Phytocoptella avellanae (Nalepa) and Cecidophycpsis vermiformis (Nalepa) 75 (Acariformes:Eriophyidae). When found in a filbert or- chard, A. aberrans was usually in high numbers and well dispersed throughout the planting. The latter observation was possibly due to A. aberrans' phoretic relationship with the filbert aphid, Myzocallis coryli (Goeze)(Krantz, 1973) . Whether A. aberrans' high abundances in moderately and highly treated filbert orchards was due to resistance or to refuge provided from its usual occurrence within the buds of the trees is unknown. Dabrowski (1970) found A. aberrans in apple orchards immediately after insecticide applications and decreasing in number after cessation of treatments. Future resistance tests and non-phoretic dispersal studies should determine the potential of A. aberrans in filbert IPM programs. Typhlodromus arboreus Mostly found on moderately sprayed apple and prune, T. arboreus populations were fairly stable in number in or- chards where they were collected. Croft & AliNiazee (1983) found low levels of resistance to OPs and carbaryl in T. arboreus in the valley, probably enough to withstand the 2- 3 sprays of a moderately treated orchard. Downing & Moilliet (1971) reportedly found morphologically similar T. columbiensis in highly sprayed apple orchards in British Columbia (T. arboreus was considered a minor species'in the same areas). While resistance explains this species' occurence in 76 some orchards, why T. arboreus had a low frequency of occurrence in certain crops throughout the valley is un- clear. Kennett & Huffaker (unpublished records) found T. arboreus on wild blackberry in California, yet T. arboreus was virtually absent on blackberry (usually a low sprayed crop) in the valley. AliNiazee (1979b) indicated that T. arboreus could numerically increase on a variety of pest mite species, thus it is not greatly limited in potential food resources. T. pyri may, however, outcompete T. arboreus on low sprayed commercial crops. T. pyri has the same spectrum of pest mite food resources as T. arboreus but the former species has been observed to utilize pollen as food (Zaher & Shehata, 1971) and can extract juices from the host plant (Chant, 1959). Whether T. arboreus can survive on various plant products is unknown. With T. arboreus' local high abundances in some or- chards and recorded resistance levels, this species may be useful in some IPM programs in the Willamette Valley. Amblyseius fallacis A. fallacis was found almost exclusively on straw- berry and corn. It was the most abundant phytoseiid on strawberries. It was always collected in low numbers at individual sites. A. fallacis' absence in arboreal crops may be due to the low humidity of the valley during mid and late season. Downing & Moilliet (1974) observed that A. fallacis did not survive well in commercial apple or- chards of the Okanagan Valley, British Columbia, which has 77 a similar climate to that of the Willamette Valley during mid and late season. Strawberries would provide more humid habitats for A. fallacis throughout the season in comparison to arboreal crops. Corn in the valley is heavily irrigated and could provide sufficient humidity for survival of A. fallacis. A. fallacis' low numbers in moderately sprayed straw- berry fields may indicate low levels of resistance. Sur- vival of A. fallacis in places of refuge and/or re- establishment of the species in the field, following insecticide treatments, from surrounding vegetation can not be ruled out. Tet. urticae, a preferred prey of A. fallacis (Burrell & McCormick, 1964), was a common pest on straw- berry and corn in the valley. This pest could facilitate use of A. fallacis in IPM programs on these crops, pro- vided A. fallacis has developed adequate levels of resistance in the valley. Highly resistant strains from other regions could be imported and established on Willamette Valley strawberry fields (Croft, 1972). Amblyseius 'complex' All species in this 'complex' have been previously collected from strawberry (Chant, 1959). All occurrences of these species were in low sprayed corn or strawberry fields and were likely due to dispersal from nearby vegetation. This group probably represents 'transients', which remain in the crop until eliminated via pesticides. 78 The 'complex's' exclusive abundance on strawberry and corn is probably due to the humidity factor, like that of A. fallacis. Mite Management in the Willamette Valley With the average number of insecticide applications lower for Willamette Valley crops than for similar crops of other regions of the U.S. (probably due to the rela- tively cool summer temperatures in the valley), there is great potential for using phytoseiid mites to help control acarine pests of commercial crops in the valley. On apple, prune and cherry, local spray programs will play a key role in determining the feasibility of IPM pro- grams for mites. If orchards have a long past history of many insecticide treatments, T. pyri may have developed enough resistance to survive in those orchards. If not, then T. occidentalis may be present. Use of chemicals detrimental to both species, such as dimethoate, should be avoided as should new compounds (e.g.-SPs (AliNiazee & Cranham, 1980)) whose effects on phytoseiids are detri- mental or unknown. In low sprayed arboreal crops (e.g. prune), T. pyri should be conserved. Potentials for IPM programs on peach and pear remain unclear due to the low abundances of phytoseiids collected on these crops. Willamette Valley climate tends to favor T. occidentalis late in the season. Levels of Pan. ulmi should be fre- quently monitored during this time due to T. occidentalis' 79 inability to regulate high densities of Pan. ulmi. Successes in mite management in New Zealand orchards using both T. pyri and T. occidentalis (Wearing et al., 1978) provide hope in attaining similar successful results in the Willamette Valley. On vine crops (grape, blackberry and, to a lesser extent, raspberry), T. pyri seems suitable for IPM pro- grams. T. pyri often preys on eriophyid mites (Collyer, 1964) which are major mite pests of vine crops. However, since vine crops in the valley have not previously re- ceived heavy treatments with insecticides, any such application may wreak havoc with susceptible T. pyri populations. The past successes of releasing laboratory- selected phytoseiid R-strains (Field, 1976; Thwaite & Bower, 1980; Croft, 1982) may provide an answer to this problem, provided resistance in T. pyri is a stable phenomenon. However, dilution of the R-strain via immi- gration and cross-breeding by wild S-strains would pose problems for such establishments within low spray crops. A. aberrans may be utilized in a program for control of eriophyid bud mites on filbert. Chant (1959) con- sidered A. aberrans ineffective in controlling Phy. avellanae, but this has not been confirmed by further research. A. aberrans often shares the same microhabitat as its prey and its phoretic relationship with the filbert aphid aids in its dispersal throughout the orchard. Both 80 of these factors are important for biological control successes (Huffaker et al., 1970). Tests to determine the level of resistance to commonly-used insecticides is necessary to further evaluate A. aberrans' potential in IPM programs for filbert pests. Strawberry supported the greatest number of phyto- seiid species, with A. fallacis the most abundant. Whether this species would be the best in an IPM program for this crop is unknown, since it was usually collected in low numbers. While used in mite management programs on apple in the eastern U.S. (Croft & McGroarty, 1977; Weires et al., 1979), A. fallacis has not been used in IPM pro- grams for strawberry. However, T. occidentalis was con- sidered to have potential for use in IPM of strawberry pests in California (Huffaker & Flaherty, 1966). Without further research concerning A. fallacis' habits and re- sistance levels in the Willamette Valley, it may be more practical to initially attempt to use T. occidentalis in new strawberry IPM programs in the Willamette Valley. As noted earlier, OP-resistant A. fallacis could be imported for use in strawberry if native T. occidentalis proved to be ineffective. Corn and mint, both representing crops that undergo high levels of cultural perturbation, may require yearly releases of phytoseiids if control of Tet. urticae (the most common mite pest of both crops) using fewer or no 81 sprays is to be achieved. This may be economically un- feasible as costs of natural enemy augmentation would probably exceed benefits for these crops. In summary, this study represents the first step in organizing an IPM program for mites in the Willamette Valley. While the future outlook for developing such programs is good, much research remains to be done. Many areas needing work have already been identified and other factors of importance include surveying the effect of commonly-used fungicides on both phytoseiids and pests and educating growers about the possible benefits of such a program. 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Species App Pch Per Prn ChrGrpBkbRsbStb Crn Mat Fbt Xtr TOTAL T. pyri 144 16 6 115 32 144 117 31 8 0 0 3 0 616 T. occidentalis 83 8 20 10 63 4 5 7 3 1 6 2 0 212 A. andersoni 7 1 2 1 22 3 19 33 8 10 1 0 11 118 A. ahPrrans 1 0 0 1 0 0 0 0 0 0 0 159 0 161 T. arboreus 38 0 0 9 0 0 1 0 0 0 0 2 0 50 A. fallacis 1 0 0 0 0 0 0 0 22 7 0 0 0 30 A. brevispinus 0 0 0 0 0 0 0 0 1 2 0 0 0 3 A. reticulatus 0 0 0 0 0 0 0 0 3 0 0 0 0 3 T. rhenanoides 0 0 0 0 0 0 0 0 0 0 0 1 0 1 A. zwoelferi 0 0 0 0 0 0 0 0 1 0 0 0 0 1 A. umbraticus 0 0 0 0 0 0 0 0 1 0 0 0 0 1 Unknown 9 1 0 0 0 0 2 0 0 0 0 1 0 13 TOTALS 283 26 28 136 117 151 144 71 47 20 7 168 11 1209 95 Appendix 2: Dichotomous key of adult female phytoseiid mites found in 1983-1985 survey of Willamette Valley, OR commercial crops. (Modified from Chant, 1959; Chant & Hansell, 1971; Chant et al., 1974) 1.- Six pairs of prolateral setae on dorsal shield (setae j3,z2,z3,s3,s4,s6)(Fig. 16) (Genus Typhlodromus Scheuten)2 - Four pairs of prolateral setae on dorsalshield (setae j3,s2,s3,s4)(Fig. 17) (Genus Amblyseius Berlese)5 2.- Eight pairs of lateral setae on dorsal shield (setae S1,S2,S4 absent)(Fig. 18). Two pairs of setae on sternal shield. Locally common, collected from apple, prune, filbert, blackberry T arboreus Chant - More than eight pairs of lateral setae ondorsal shield 3 3.- Ten pairs of lateral setae on dorsal shield (seta S1 absent)(Fig. 20). Rare, one individual collected from moss on filbert T rhenanoides (A.-H.) - Nine pairs of lateral setae on dorsalshield 4 4.- Setae on dorsal shield short (Fig. 22). Posterior setae on interscutal membrane (R1) present. Common, found on almost all surveyed crops T pyri Scheuten - Setae on dorsal shield long(Fig. 24). Posterior setae on interscutal membrane (R1) absent. Common, found on almost all surveyed crops. especially those receiving multiple insecticide treatments T occidentalis Nesbitt 5.- Less than nine pairs of lateral setae on dorsal shield (setae S4 absent)(Fig. 26). Common, collected almost exclusively on filbert A aberrans (Cude.) 96 - Nine pairs oflateral setae on dorsal shield 6 6.- Some setae on dorsal shield much longerthan others (Fig. 28). Common, found on almost all surveyed crops, especially those receivingfew insecticide treatments A andersoni (Chant) - All setae ondorsal shield short, none greatly longer than the others 7 7.- Setae j4,j5,z5,j6 longer than distances betweentheir bases (Fig. 30). Collected mostly from strawberryand corn A fallacis (Garman) - Setae j4,j5,z5,j6shorter than distances between their bases 8 8.- Prolateral setae (j3,s2,s3,s4) approximatelyequal to distances between their bases (Fig. 32). Rare, one specimen collected from strawberry Aumbraticus (Chant) - Prolateral setae(j3,s2,s3,s4) much shorter than dis- tances between their bases 9 9.- Moveable digit of chelicera with single smalldenti- cle (Fig. 36). Rare, one specimen collected from strawberry and two collected from corn Abrevispinus (Kennett) - Moveable digit ofchelicera without denticle 10 10.- Large species (440u+). Atrium of spermathecabell- shaped (Fig. 39). Lateral margins of ventrianal shield slightly constricted (Fig. 38). Rare, one specimen collected from strawberry A zwoelferi (Dosse) Smaller species (less than 400u). Atrium of sperma- theca elongate (Fig. 42). Lateral margins ofventri- anal shield rounded (Fig. 41). Three specimenscol- lected from strawberry A reticulatus Oude. 97 Figure 16: Dorsal shield of Typhlodromus sp., show- ing chaetotactic nomenclature. Figure 17: Dorsal shield of Amblyseius sp.,show- ing chaetotactic nomenclature. 98 19 Figures 18-19: Typhlodromus arboreus;(18) dorsal shield,(19) ventrianal shield. 99 20 21 Figures 20-21: Typhlodromus rhenanoides;(20) dorsal shield,(21) ventrianal shield. r 100 22 Figures 22-23: Typhlodromus pyri;(22) dorsal shield,(23) ventrianal shield. 101 25 Figures 24-25: Typhlodromus occidentalis; (24) dorsal shield,(25) ventrianal shield. 102 ier I 4\ 1 I 26 27 Figures 26-27: Amblyseius aberrans;(26) dorsal shield,(27) ventrianal shield. 103 Figures 28-29: Amblyseius andersoni;(28) dorsal shield,(29) ventrianal shield. 104 30 Figures 30-31: Amblyseius fallacis;(30) dorsal shield,(31) ventrianal shield. 105 33 Figures 32-33: Amblyseius umbraticus;(32) dorsal shield, (33) ventrianal shield. 106 34 36 Figures 34-36: Amblyseius brevispinus;(34) dorsal shield,(35) ventrianal shield, (36) chelicera showing denticle on move- able digit (circled). 107 37 39 Figures 37-39: Amblyseius zwoelferi;(37) dorsal shield,(38) ventrianal shield, (39) spermatheca. 108 42 Figures 40-42: Amblyseius reticulatus;(40) dorsal shield,(41) ventrianal shield, (42) spermatheca. Appendix 3: Absolute abundances of major phytoseiid species found in survey of Willamette Valley commercial crops during specified seasonal time. Species Seasonal Period App Pch Per Prn Chr Grp Bkb Rsb Stb Crn Mnt Fbt Xtr TOTAL Early 65 8 4 57 11 51 42 6 4 0 0 0 0 248 T. pyri Mid 38 8 0 35 15 76 46 12 0 0 0 0 0 230 Late 41 0 2 23 6 17 29 13 4 0 0 3 0 138 Early 6 1 0 4 7 0 0 0 0 0 0 0 0 18 T. occidentalis Mid 27 1 4 4 12 0 3 7 3 1 6 1 0 69 Late 50 6 16 2 44 4 2 0 0 0 0 1 0 124 Early 0 0 0 1 3 0 2 12 3 0 0 0 0 21 A. andersoni Mid 1 0 0 0 2 1 11 5 3 8 1 0 11 43 Late 6 1 2 0 17 2 6 16 2 2 0 0 0 54 Early 1 0 0 1 0 0 0 0 0 0 0 21 0 23 A. aberrans Mid 0 0 0 0 0 0 0 0 0 0 0 73 0 73 Late 0 0 0 0 0 0 0 0 0 0 0 65 0 65 Early 21 0 0 7 0 0 1 0 0 0 0 0 0 29 T. arboreus Mid 13 0 0 0 0 0 0 0 0 0 0 2 0 15 Late 4 0 0 2 0 0 0 0 0 0 0 0 0 6 Early 0 0 0 0 0 0 0 0 12 0 0 0 0 12 A. fallacis Mid 0 0 0 0 0 0 0 0 7 1 0 0 0 8 Late 1 0 0 0 0 0 0 0 3 6 0 0 0 10 Early 0 0 0 0 0 0 0 0 4 1 0 0 0 5 Amblyseius 'complex' Mid 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Late 0 0 0 0 0 0 0 0 2 1 0 0 0 3 Lb Appendix 4: Absolute abundances of major phytoseiid species found in survey of Willamette Valley commercial crops within specified spray regimes. Species Spray Regime App Pch Per Prn Chr Grp Bkb Rsb Stb Crn Mht Fbt Xtr TOTAL Low 21 2 0103 19 82 97 19 0 0 0 3 0 346 T. pyri Moderate 47 9 2 12 5 62 19 12 6 0 0 0 0 174 High 76 5 4 0 8 0 1 0 2 0 0 0 0 96 Low 0 0 0 1 7 4 5 7 2 1 6 1 0 34 T. occidentalis Mbderate 30 6 1 3 12 0 0 0 1 0 0 0 0 53 High 53 2 19 6 44 0 0 0 0 0 0 1 0 125 Low 2 0 0 1 18 2 19 17 6 2 1 0 3 71 A. andersoni Moderate 4 1 1 0 2 1 0 16 2 8 0 0 8 43 High 1 0 1 0 2 0 0 0 0 0 0 0 0 4 Low 0 0 0 1 0 0 0 0 0 0 0 13 0 14 A. aberrans Moderate 0 0 0 0 0 0 0 0 0 0 0113 0 113 High 1 0 0 0 0 0 0 0 0 0 0 33 0 34 Low 0 0 0 4 0 0 1 0 0 0 0 2 0 7 T. arboreus Mbderate 34 0 0 5 0 0 0 0 0 0 0 0 0 39 High 4 0 0 0 0 0 0 0 0 0 0 0 0 4 Low 0 0 0 0 0 0 0 0 3 0 0 0 0 3 A. fallacis Mbderate 0 0 0 0 0 0 0 0 16 7 0 0 0 23 High 1 0 0 0 0 0 0 0 3 0 0 0 0 4 Low 0 0 0 0 0 0 0 0 6 2 0 0 0 8 Amblyseius 'complex' Mbderate 0 0 0 0 0 0 0 0 0 0 0 0 0 0 High 0 0 0 0 0 0 0 0 0 0 0 0 0 0 H 0H