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1971 Resistance of Sweet Potato Cultivars and the Effect of Cultural Methods on Control of Soil Insect Damage. Bunnie William Wascom Louisiana State University and Agricultural & Mechanical College
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WASCOM, Bunnie William, 19 33- RESISTANCE OF SWEET POTATO CULTIVARS AND THE EFFECT OF CULTURAL METHODS ON CONTROL OF SOIL INSECT DAMAGE.
The Louisiana State University and Agricultural and Mechanical College, Ph.D., 1971 Agriculture, plant culture
University Microfilms, A XEROX Company, Ann Arbor, Michigan
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED RESISTANCE OK SWEET POTATO CULTT.VARS AND THE EFFECT OF CULTURAL METHODS ON CONTROL OF SOIL INSECT DAMAGE
A Dissertation
Submitted to the Graduate. Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Horticulture
by Bunnie William Wascorn 15,S., Southeastern Louisiana University, 1950 M.S., Louisiana State University, 1964 January, 1971 Please Note:
Some pages have very light type. Filmed as received.
University Microfilms. ACKNOWLEDGEMENT
The writer wishes to express his sincere appreciation to Dr.
Julian C. Miller for making this study possible. The author is especially grateful to Dr. Teme P. Hernandez under whose guidance the research was completed. Gratitude is also extended to Dr. Edmon
Kantack for his helpful suggestions and assistance in identifying sweet potato insect injury. Appreciation is extended to Aithel
McMahon, Dr. William A. Young and Cary G. Fontenot for their assist ance in field evaluations and to Mr. Wiley D. Poole for his assistance with mechanical equipment used for this study. The author is indeed grateful to the growers who assisted in this research and to many other people who contributed so much to this work.
Sincere appreciation is extended to Dr. Donald Newsom and Dr.
James Fontenot for their assistance and suggestions in preparing this manuscript and to Dr. Mike Giamalva, Dr. Travis Hernandez and Dr.
William A. Young for reviewing the manuscript.
The author is most grateful to his wife Loretta and sons Daryl,
Bradley and Wendell without whose help, patience and understanding this work would not have been possible.
ii TABLE OF CONTENTS
Page.
ACKNOWLEDGEMENT...... ii
LIST OF T A B L E S ...... iv
LIST OF FIGURES...... vii
ABSTRACT...... viii
INTRODUCTION...... '...... 1
REVIEW OF LITERATURE ...... 3
Preference and Non-Preference . . . 5 Antibiosis...... 10 Tolerance...... 13 Sweet Potato Insects...... 14
MATERIALS AND METHODS...... 20
Field Evaluations of Cultivars...... 20 Mulch Studies...... • 21 Feeding Studies ...... 23 Greenhouse Feeding Study...... 24 Genetic Study ...... 25
RESULTS...... 26
Field Evaluation of Cultivars ...... 26 Banded Cucumber B e e t l e ...... 2.6 Pale-striped Flea Be e t l e ...... 34 Wireworm and Surface Mining...... 35 Sweet Potato Flea Bee t l e ...... 38 Grubs...... 40 Sweet Potato Weevil...... 41 Mulch Studies...... 41 Feeding Studies ...... 42 Genetic Studies...... 44
DISCUSSION OF RESULTS ...... 76
SUMMARY AND CONCLUSIONS...... 82
BIBLIOGRAPHY ...... 85
AUBIOCRAPUY...... 91
iii LIST OF TABLES
TABLE Page
1. Severity indices of sweet potato root injury by larvae of Diabrotica baltcata on cultivars at Lewisburg, Louisiana...... 45
2. Severity indices of sweet potato root injury by larvae of Diabrotica baltcata on cultivars at the Hill Farm, L.S.U., Baton Rouge, Louisiana...... 46
3. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Scott, Louisiana . 47
4. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Arnaudville, Louisiana...... 47
5. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at the Hill Farm, L.S.U., Baton Rouge, Louisiana...... 48
6. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Scott, Louisiana . 48
,7. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at the L.S.U. Quail Farm, Baton Rouge, Louisiana...... 49
8. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Arnaudville, Louisiana...... 50
9. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Kidderville, Louisiana...... 51
10, Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Ville Platte, Louisiana...... 52
11, Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Grand Coteau, Louisiana...... 53
12, Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Hessmer, Louisiana...... 53
iv TABLE Page
13. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Clinton, Louisiana...... 54
14. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at the L.S.U. Hill Farm, Baton Rouge, Louisiana...... 55
15.. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at St. Gabriel, Louisiana...... 56
16. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at L.S.U. Ben Hur Farm, Baton Rouge, Louisiana...... 57
17. Mean severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars from several locations in Louisiana, 1965...... 58
18. Percent and mean percentages of roots with injury caused by banded cucumber beetle larvae in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966. 59
19. Severity and mean severity indices of roots with injury caused by banded cucumber beetle larvae in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966. 60
20. Severity and mean severity indices of roots with injury caused by pale-striped flea beetle larvae in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966. 61
21. Percent and mean percentages of roots with injury caused by wireworms in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966 ...... 62
22. Percent and mean percentages of roots with surface mining in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966...... 63
23. Wireworm and mining injury on roots of sweet potato cultivars at Lawtell, Louisiana, 1965 ...... 64
24. Percent and mean percentages of roots with injury caused by sweet potato flea beetle larvae in sweet potato cultivars at 5 locations in Louisiana, 1966. .. . 65
v TABLE Page
25. Percent: and mean percentages of roots with injury caused by grubs in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966 ...... 66
26. Percent of roots with injury caused by sweet potato weevils in field-grown sweet potato cultivars at Scott, Louisiana, 1966 . 67
27. Effect of black plastic mulch and cultivars on the severity of sweet potato root injury by Diabrotica balteata, Scott,: Louisiana...... 68
28. Effect of black plastic mulch and cultivars on the severity of sweet potato root injury by Diabrotica balteata, Church Point, Louisiana ...... 68
29. Effect of black plastic mulch and cultivars on the severity of sweet potato root injury by Diabrotica balteata, Lewisburg, Louisiana...... 69
30. Effect of mulches on the severity of Centennial sweet potato root injury by Diabrotica balteata, Essen Lane Farm, Baton Rouge, Louisiana...... 69
31. Effect of cultivars on the mean injury of sweet potato roots by larvae of Diabrotica balteata in controlled environment, Louisiana State University, Baton Rouge, Louisiana, 1964 ...... 70
32. Severity indices of sweet potato root injury by larvae Diabrotica balteata on greenhouse-grown cultivars at L.S.U., Baton Rouge, Louisiana...... 71
33. Study of resistance of seedlings from a cross of L3-64 x Nemagoldand other cultivars to banded cucumber beetle injury . 72
vi LIST OF FIGURES
FIGURE Page
I. Frequency distribution cf sweet potato seedlings into classes as to resistance to banded cucumber beetle larvae in a cross of L3-64 x Nemagold...... 75
vii ABSTRACT
Studies were conducted from 1964 through 1966 to determine the
resistance of fleshy roots of sweet potato cultivars to injury by
larvae of the banded cucumber beetle and certain other insects under
field conditions. In 1964 mulches were investigated in field experi ments as a means of reducing injury to sweet potato storage roots.
Also, an attempt was made in 1964 to develop a suitable laboratory
technique for screening sweet potato cultivars for resistance to
larvae of the banded cucumber beetle. A controlled greenhouse
banded cucumber beetle larvae feeding study to screen sweet potato
breeding lines for resistance was initiated in 1964 and completed in
1965. A progeny of seedlings from a cross of L3-64 x Nemagold were
tested in 1965 for resistance to banded cucumber beetle larvae.
A severity index was calculated for each cultivar by the
following formula:
Severity index = Summation of (No. of roots in each class x class No.) No. of classes -1 x No. of roots classed
Injury classes are as follows: 0 = no Injury; 1 = 1 feeding
injury; 2 = 2 to 5 feeding injuries; 3 = 6 to 10 feeding injuries;
4 = 11 to 20 feeding injuries; and 5 = over 20 feeding injuries per
root.
Statistical analyses were calculated on all experimental data
and .05 and .01 levels of significance were considered as the most
acceptable differences.
viii In 1964 numerous cultivars were field tested at four locations in Louisiana to determine differences among cultivars in fleshy root injury by larvae of the banded cucumber beetle. L3-64 consistently had significantly less fleshy root injury than most other cultivars tested; whereas, Centennial, an accepted commercial variety consistently had severe damage.
The data obtained in 1965 from 10 field tests showed that L3-64 had an average severity index of 4.5 compared to an average severity index of 19.3 for Centennial.
In 1966 roots of L3-64, as an average of five locations, had the least amount of injury by larvae of the banded cucumber beetle.
Results from mulching experiments showed no significant differ ences among mulch treatments.
Results from a controlled feeding study with banded cucumber beetle larvae showed large differences in root injury among cultivars.
L4-89 and L9-125 had significantly fewer roots damaged than Centennial.
In this test L3--64 had a lower severity index than Centennial and this difference approached significance.
Forty-one cultivars were evaluated for resistance to banded cucumber beetle larvae in a greenhouse experiment. The. larvae were introduced into the beds of growing plants on five different dates.
In addition, adult beetles with clipped wings were introduced into the beds on one date. Although there were no significant differences among cultivars, severity indices ranged from a low of 3.33 for Jersey
Orange to a high of 36.30 for Centennial. L3-64 had a severity index of 9.00 and in general those cultivars with L3--64 as a parent had low severity indices. ix A genetic study was conducted in 1965 to determine the inheri tance of resistance to larvae of the banded cucumber beetle. The data indicated that this character was inherited quantitatively. There were 15.3 percent of the seedlings rated as very resistant, 29.9 percent resistant, 22.6 moderately resistant, 17.5 percent moderately susceptible, 9.0 percent susceptible and 5.7 percent very susceptible.
The results.obtained from studies in 1966 showed that in general,
L3-64 consistently suffered relatively little fleshy root injury from larvae of the .pale-striped flea beetle, sweet potato flea beetle, the wireworm, surface mining, grubs and the sweet potato weevil.
x INTRODUCTION
The sweet potato Ipornea batatas L. is subject to injury by both foliage and fleshy root feeding insects. Since the fleshy root is the edible and marketable portion of this plant, it is important that they be as injury free as possible. Soil insect injury to the sweet potato, especially fleshy roots, has been of increasing importance since 1959
(42, 43) and limited studies have been made relative to- injury by the banded cucumber beetle, Diabrotica balteata Lee.
Growing resistant cultivars is the ideal way to protect the sweet potato from this insect. There is an increasing need for breed ing crops for resistance to insects since the Food and Drug Administra tion is getting more stringent on regulations governing the use of pesticides. Limited research relative to breeding for resistance to insects has been due partly to the availability of effective and economical insecticides to control most sweet potato insects.
There is an increasing interest in insect resistance in plants and because of the pressi.ng needs of this type of research, these
studies were initiated.
Numerous field experiments involving many cultivars were con ducted to evaluate cultivars relative to their injury to the fleshy roots by banded cucumber beetle larvae. Two feeding studies, one in
the greenhouse and another in the laboratory were conducted in an effort to screen and select resistant sweet potato cultivars as germ- plasm for breeding purposes.
1 Several synthetic, mulches were used to determine their effect
in controlling fleshy root injury by larvae of the banded cucumber beetle.
Also, a genetic study was conducted to evaluate the resistance
of segregating seedlings to banded cucumber beetle larvae injury. REVIEW OF LITERATURE
Painter (68) in 1968 noted that the spectacular success of newer
types of insecticides that were developed during and after World War II
have tended to obscure the fact that there are many other ways by which insects can be controlled. He stated that because the litera
ture on insect resistance has been so widely scattered, the results of
the combined efforts of entomologists and plant breeders are not
generally known. Evidence presented by this author also indicates
that, in a number of cases control by hos.t-plant resistance as measured
by yield compared favorably with control by insecticides. Some insects,
such as the grape phylloxera, may be satisfactorily controlled by host-
plant resistance, but so far, not by insecticides. He also mentioned
that differences in responses of plant varieties to insect attack and
the interrelations of plants and insects have been on record for more
than a hundred years.
An outstanding example of crop resistance to insects as a major means of control is demonstrated by the case in France of the grape
phylloxera Phylloxera vitafoliae Fitch, reported by Howard (33) in
1930. Shortly thereafter, phylloxera resistant grape vines were sent
to France from the United States and the use of phylloxera resistant
grapes remains an important method of controlling this insect.
Snelling (70) suggested that certain plant characteristics had
an influence in resisting insect attack and he concluded that a number
of factors were involved.
3 Painter (61, 62) emphasized the insect-plant interrelations as
features of importance in considering insect resistance and he
attempted to classify factors responsible for resistance. For example,
various environmental factors may act primarily on the insect, the
plant or the insect-plant relationship. He divided the phenomenon of
insect resistance in plants as seen in the field into three mechanisms.
They were: (1) Preference or Non-preference, (2) Antibiosis, and
(3) Tolerance. He illustrated this in the following diagram:
Preference or Non-preference Antibiosis (For oviposition, f o o d ------£*. (Adverse effect of plant or shelter) on biology of insect)
(Repair, recovery, or ability to withstand infestation)
He also said that one or a combination of any of the three mechanisms
are present in most cases of resistance that have been sufficiently
studied. Preference or non-preference refers to a group of plant
characters and insect responses that lead to or away from a particular variety for oviposition, food, shelter or a combination of the three.
Antibiosis is the tendency to prevent, injure, or destroy insect life.
The effects on the insect take the form of reduced fecundity, decreased
size, abnormal length of life, and increased mortality. The latter usually appears in those stages just preceding the adult stage.
Tolerance refers to resistance in which the plant shows an ability to grow and reproduce itself or to repair injury to a marked degree even when supporting a population approximately equal to that damaging a
susceptible host. Painter (61, 62) stated that this basic triad of resistance relationships usually have been found to result from independent genetic characters which are interrelated in their effects. A variety not preferred does not require the degree of antibiosis or tolerance that must be present in a preferred variety of the same level of resistance. A plant exhibiting high tolerance and low antibiosis toward a particular insect may show the same level of resistance as one that has a high degree of antibiosis and an average degree of tolerance. In any given variety genes for one or more of these charac teristics may be present, but sometimes others will be found in other varieties. The cumulative resistance by recombinations of genetic factors for different types of resistance is possible. The expression of the genetic factors resulting in three characteristics discussed herein is frequently modified by various ecological conditions and by other genes. The separation of pseudoresistance from true genetic resistance and the determination of the approximate proportion of resistance due to each of the three above characteristics is of early and primary importance in any serious study of resistance.
Preference and Non-Preference
Experiments by Broadbent (5) in 1949 provided no evidence in favor of the theory that the olfactory sense is used by aphids to find their host, nor were flying aphids attracted to other Myzus persicae
Sulz. or to the honeydew on the host. He suggested that it is probable that the host is found by chance, and that having found it the aphids move about the plant until they find a favorable leaf on which to remain. Indications were that the aphids tend to group aiid remain in association when they meet during crawling.
Kennedy (48) and Uvarov (72) discussed in detail the sensitivity of insects to various stimuli and their conditioned responses.
Von Frisch (25) as reported by Painter (63) noted that when the behavior of insects with respect to light was analyzed carefully, different responses to the different physical attributes of light were found: direction, intensity, wave length or color, and in some instances the direction of the oscillations of polarized light.
Weiss et £l_. (76) exposed seven species of Goleoptera to ten wave length bands of light of equal physical intensities. They noted that the peak response for all species except one took place in the ultra-violet (3650-3663 A°) and that secondary peaks occurred either in the blue-blue-green (492.0 A°) or in the blue-green (5150 A°). As a whole, the behavior of the adults and larvae did not differ appre ciably.
Painter (63) reviewed the work of Gotz (26) and reported that on the basis of his work and others lepidopterous larvae tended to depend on sight and differentiation of shapes rather than smell or taste as a means of finding food. Gotz (27) also reported that cater pillars of the butterflies (Vanessa io L., V. urticae L., and Pieris brassicae L.)were attracted to green pieces of paper during the feeding period but failed to respond in that manner when they were ready to pupate.
Jones e_t al_. (38) found that three plant characters tended to determine the thrip population on onions. Those characters were shape 7
of leaves, the angle of divergence of the two innermost leaves, and
the distance between the leaf blades on the sheath column.
Cody (8) compared 17 pea varieties used for freezing in Oregon
and found greater infestations of the pea aphid Illinoia pisi
Kaltenbach to occur on medium green and dark green varieties than on
the lighter green varieties.
Research by Isely (35) in 1925 and 1926 indicated that the boll weevil had a greater preference for cotton plants with green foliage
than those with red foliage. He further stated that the boll weevil had little choice between small and large leafed varieties, provided
the size and vigor of the plants were about the same.
Isely (36), and Harrison and Brubaker (30) reported that infes
tations of cabbage looper and the imported cabbage worm were heavier
on red leafed cabbage than on green leafed varieties. They stated
that no outstanding resistance was shown regardless of the foliage
color.
Investigations by MacLeod (51) suggested that celery varieties with green leaves and stems were more resistant to damage caused by
the tarnished plant bug than varieties with yellow colors.
Moore (56) found that aphids Myzus persicae Sulz. were attracted
to potato plants when sprayed with Bordeaux and attributed this to
increased intensity of light reflected from the sprayed surfaces. He
also found that infestations of the cabbage aphid Brevicoryne
brassicae L. on dusted plots could be reduced below those on untreated
plots by dyeing the dusts. Black dust was found to be the most effec
tive in reducing infestations. These experiments suggested that
spraying and dusting practices on crops infested with aphids may be profitably modified by the use of dyed materials to produce a reduction in the intensity of light reflected from the treated surfaces.
Findings submitted by Annand (2) showed that aphid resistance in cotton was coupled with glabrous leaves. The location of hair on the leaf was more important than average pilosity of the leaf. The strains of cotton with the greatest number of hair on the veinlets were more susceptible to aphids because they afforded the insect more protection from adverse weather conditions.
Hamlin (28) studied the prickly pear insect to determine its feeding habits and choice of plants for oviposition. He found that physical similarity of the host plant rather than botanical relation ship or chemical characteristics influenced the preference of the cactus feeding insect.
Currie (12) made a study of the oviposition habits of the cocklebun: seed fly or Xanthium burrs. Ha found that when the charac teristic spines of the burrs were removed the insect was not attracted, but, that the female would attempt to oviposit on an artificial burr made of rubber and pins. During this study it was also observed that females would not oviposit on flat surfaces containing spines similar to those of the cockleburr, suggesting that shape of plant parts con tributed to this insect choice of oviposition site.
Cunliffe and Hodges (13) found that the amount of separation of the coleoptile from the young oat plant was an important factor in determining the severity of infestation by Oscinella frit L.
McColloch (52) provided evidence to show that the moths of the
European corn borer have a preference for the silks of corn for ovi position. When these were not available, the upper surface of the leaves and the stalks were selected. Relatively few eggs were deposited on the lower surface of the leaves, husk or tassel. There was however, a distinct relation between the date of planting and the number and location of the eggs.
Laboratory tests were conducted by Mclndoo (50) to determine the relative attractiveness of leaves of four species of solanaceous plants to larvae and adults of the Colorado potato beetle Leptinotarsa decemlineata Say. The relative attractiveness of these leaves appeared to depend on the species of plant on which the insect had fed prior to the determination of their responses.
Investigations by Richmond in 1937 (66) and Langford ejt _al_. in
1943 (49) found geraniol, an extract of sassafras and certain other plants, to be an excellent attractant of the Japanese beetle.
Metzger et al_. (55) analyzed material from 97 species and varie ties of plants for reducing sugar content in order to determine the relationship between sugar content of the plant and its susceptibility to attack by the Japanese beetle. They found that in general, those extracts having the higher sugar content with fruity odors were most desirable. The nature of the substance causing the fruity odor was not determined.
Metzger and Grant (54) tested 474 plant extracts, representing
390 species from 326 genera and 108 families and found 56 of them to show some repellency potential.
Investigations by Sleesman (68) showed Solanum sohyadenium to be highly resistant, if not immune, to attack by the potato leafhopper.
This resistance was attributed to the disagreeable odor due to an oil or ester on the upper and lower leaf surfaces and on the stem parts. 10
The odor was found to be very strong on the younger leaves but much less pronounced on the mature ones.
Carter (7) presented data to show that extremely high sap con centrations were undesirable to and avoided by the sugar-beet leaf- hopper if more suitable food was available. This was true in a small area, where two growth forms of the same species were present the higher concentrations forms were abandoned for those having a lower coccentration.
Also, indications were that if another host plant was found with a more suitable sap concentration than the original host plant, the original host was abandoned and the new host supported a greater insect population.
Fife and Frampton (24) found that the leafhopper Eutettix tenellus Baker feeding under normal conditions, was probably guided to the phloem by the pH gradient. The results of this study showed that the insect prefers an alkaline food rather than one that is acid.
Antibiosis
Dahms and Martin (20) studied resistance of sorghum varieties to chinch bugs by comparing the number of eggs laid by the females on different varieties. Chinch bugs confined on stems of field grown susceptible varieties laid more eggs than those on resistant varieties.
Data from crosses suggested that resistance in the Fi plants was inherited as a dominant character.
Hughes (34) confirmed the earlier work of Ivanoff (37) showing that aphid Aphis gossypii, Glov. resistance in cantaloupe was inherited as a mendelian dominant factor. 11
Isely, (36)■found that moths of the corn aarworm reared from
larvae fed on corn were larger and had a greater fecundity than those
reared from other host plants. Moths reared from worms fed on green
corn and kept at 25° C, during their adult lives deposited on an
average of 1848 eggs, or more than twice as many as those reared on
any other host.
A study by Harrington (29) on the influence of aphid resistance
in peas revealed that a resistant variety slightly reduced the rate of
aphid development, inhibited reproduction t:o a considerable extent,
and decreased aphid longevity.
Brues (6) noted that the food choice of the Colorado Potato
beetle was not always compatible with larvae requirements.
In 1946 Hill (31) studied the effects of different food plants
on the fecundity, adult longevity and larval development of the tuber
flea beetle, Epitrix tuberis Gentner and he found large differences
among plants.
Dahms (22) found that chinch bugs laid more eggs when feeding on
one variety of sorghum than on any of the other eight varieties in tlie
experiment. Longevity of females varied depending on the variety on which they were feeding. Nymphs reared on susceptible varieties were
larger than those reared on resistant ones. The study also revealed
that, more eggs were laid on 45-day old plants and plants in the heading
stage than on 25-day old plants and that they lived a shorter length
of time on the 25-day old plants. When chinch bugs were reared in
field cages the adults were larger on susceptible varieties and in
general those reared on headed sorghum were smaller than those grown
on younger plants. Nymph development varied with variety but the age 12 of plants clid not affccl. the rate of growth. The author-believed
that the condition of the cell sap rather than any readily observable morphological characters of the plant was responsible for the differ ences observed on the biology of the chinch bug when feeding on different varieties and ages of sorghum. Whether these differences were due to absence, presence, or quantities of certain food materials
in the cell sap was not known.
Trager (71) discussed insect nutrition and the need for accessory
growth factors. He stated that most of the species which have been
studied appear to require only one fat-soluble factor, cholesterol.
Certain other sterols can replace cholesteral in some species of
insects, but, it cannot be replaced by sterols of the vitamin D group.
Various salts also appear to be essential constituents of the diet for most insects.
Painter (63) reviewed the work of Coon, et al. (10) and reported that a correlation was shown between the amount of carotene in inbred
lines of corn and resistance to the corn leaf aphid.
In preliminary feeding studies Hodge (32) found that the differ ential grasshopper, Melanoplus differentialis Thomas had definite nutritional requirements necessary for proper growth and development.
Dahms and Painter (21) reported that reproduction of the pea aphid was greater on flowering stems of alfalfa than on vegetative branches of the same plant. The aphid reproduced more rapidly and the mortality was lower on susceptible than resistant varieties. Some alfalfa plants which appeared to be resistant furnished satisfactory
food for aphid reproduction. This resistance may be because of the plants ability to withstand the feeding damage of aphids. 13
Pepper arid Hastings (64) pointed out that fertility of females of the sugar beet webworm was influenced by the food of the larvae.
Plants high in linoleic acid resulted in females of higher fertility.
It is the belief of these authors that this fatty acid is essential
for normal development and reproduction, and it cannot be synthesized by the insect.
According to Beck e_t al. (3) growth rate of newly hatched larvae of the European corn borer varied greatly when the diet of this insect was altered.
Tolerance
Experiments and observations by Snelling et^ al. (69) indicated that resistance in sorghum consisted of physiological characters involving at least in part the ability of a variety to grow or recover in spite of the feeding of chinch bugs.
Painter et al. (60) reported that corn hybrids were more resistant to injury by the chinch bugs than their parental inbred lines. It may be that the ability of corn to survive under conditions of infestation is due to one or both of two separate conditions:
(1) inherited specific resistance to chinch bugs; and (2) tolerance to or escape from injury associated with heterotic vigor.
The findings of Coon (9) indicated that varieties of soybeans studied were found susceptible to Japanese beetle attack. However, late maturing varieties recovered from the beetle injury by continued growth after the beetles had disappeared. Earlier varieties failed to make this recovery that resulted in decreased yields. 14
Cunliffe (11) simulated injury on two oat varieties to that caused by the fruit fly. He compared the yields and number of tillers
and found that the variety which was the least desirable exhibited a pronounced ability to recover from the plant damage and it outyielded
the normally prolific variety.
Mungoir.ery and Buzacott (59) mentioned that resistance of some
sugarcane varieties to cane grubs was attributed to their ability to readily replace injured roots and to the. plants extensive root system.
Went (77) discussed malformations on plants caused by insects as a result of either increased or decreased growth. A good example is crinkling of leaves caused by aphids. He explains the decreased growth was the result of auxin destruction in the phloem. In cases where excessive elongation of cells or organs occurred he attributed this to increased auxin content of the reacting tissue.
Allen (1) concludes that plant growth regulating substances may help to explain the nature of toxin activity following insect feeding.
These growth substances will in some instances produce changes similar to those caused by insects. They show a close resemblance in enzymatic activity and will inhibit abscission caused by certain insects.
In 1941,"Evans (23) discovered that cabbage infested by the aphid,
Brevicoryne bassicae L. had a marked decrease in the amount of carbo hydrate synthesized but smaller decreases in fat, crude protein and other constituents.
Sweet Potato Insects
Shorey and Anderson (67) conducted studies on the biology and control of the larvae of the morning-glory leaf miner, BedeIlia 15
somulentclla Zell, which caused extensive damage to the foliage of
sweet potatoes in San Diego County, California, during 1959. Bio
logical studies revealed that there were five larvae instars. The
first and second instar larvae form a serpentine mine; larvae of the
last three instars formed blotch mines during the course of their development. The larvae were controlled chemically by the use of
toxephene, Dylox (dimethyl 2,2,2-trichloro-l-hydroxyethylphosphorate), parathion, malathion, DDT, or Diazinon AT, 0-diethyl 0-(2 isopropyl-
4-methy 1 - 6-pyrimid iny 1) phosphorothioate7.
In 1946 Macrovitch (53) maintained that several species of
insects in Tennessee were capable of causing holes in sweet potatoes.
It appeared that the elongate flea bettle larvae and possibly the
larvae of the pale-striped flea beetle were present in large numbers.
Brett et al_. (4) pointed out that wireworms have developed a resistance to widely used cyclodiene insecticides in some areas of
North Carolina and that DDT effectively controlled resistant wireworms.
Preplant incorporated applications of Diazinon resulted in poor con
trol, but a foliage-surface application in July proved successful.
Certain other insecticides showed promise. Soil type influenced effectiveness of incorporated treatments of insecticides but not
surface applications.
Walker (73) obtained evidence to show that when male sweet potato weevils, Cylas formicarius elegantulus Summers, were exposed
to 18,000 R of gamma rays and then mated with untreated virgin females,
egg hatch was reduced to less than one percent. Irradiated males com peted favorably with untreated males for virgin females. Matings
involving 4 sterile males, 4 untreated males, and 4 untreated virgin 16
females had an average of 55 percent egg hatch. There was no subse quent reduction in the number of progeny produced when virgin females were first mated with untreated males and later with irradiated males.
Kantack (40, 41) reported that he had obtained good soil insect control in sweet potatoes in 1957 and 1958 by the use of aldrin and heptachlor.
Observations by Kantack (42, 43) in 1959 indicated that damage
to sweet potato roots caused by the. sweet potato flea beetle and the banded cucumber beetle were severe in some areas of Louisiana. Wet growing conditions, resulting in grassy fields and excellent sites for
insect oviposition, were suggested as a contributing factor to increased root damage. He indicated that resistance to aldrin and heptachlor by the larvae of these two insects may have increased also.
Kantack (46) discussed sweet potato insect investigations with reference to both foliage feeding and soil inhabiting insects.
Kantack (44, 45) note;d that most of the injury on sweet potato roots in Louisiana in 1960 resulted from feeding by larvae of the banded cucumber beetle on immature roots. The sweet potato flea beetle larvae caused some late season root injury. Prevention of root injury by the use of insecticides was difficult. The author remarked that greater acreages of early maturing varieties, varieties attractive to adult banded cucumber beetles, increased soybean acreage in which first insect generations emerge, and killing of predators with insecticides may have contributed to the increased banded cucumber beetle population.
Montelaro ed: al_. (57, 58) directed attention to foliage feeding, soil-inhabiting, and storage insects that attack sweet potatoes. They discussed control measures and injury characteristic of the insects. Insecticide studies in sweet potatoes by Kantack (47) revealed that Thiodan sprayed into the top 3 inches of soil on a 16-inch band at one pound per acre preplanting resulted in production of marketable roots whereas roots of the check plots were injured 100 percent by the larvae of the banded cucumber beetle. Telodrin looked very promising and Endrin gave only moderate protection. Centennial roots were more severely injured by larvae of the banded cucumber beetle than was
Unit 1 Porto Rico. Cultivar L3-64 had very little injury compared to others tested.
Cuthbert and Reid (14) directed attention to laboratory tests with insecticides for the control of larvae of the banded cucumber beetle. They found that in general, organic phosphate compounds were most- toxic to larvae of this insect. The commonly used chlorinated hydrocarbons were relatively ineffective.
Pitre and Kantack (65) reported that the banded cucumber beetle
Diabrotica balteata, LeConte was an increasingly important pest on sweet potatoes in Louisiana since 1958. There were 6 or 7 generations produced per year in Louisiana and beetle activity was observed during every month of the year. Eggs were deposited in the soil singly or in clusters and in the field as many as 12 eggs were observed in a single cluster. Under laboratory conditions the researchers found that 20 to
100 eggs were laid during a 24 hour period. Oviposition usually occurred at intervals of every 2 to 3 days beginning when the female was about. 3 weeks old and continued for 2 to 8 weeks. The number of lays during which the oviposition occurred ranged from 2 to 15, a single female laying as many as 849 eggs in a life time. Three larvae 18 instars were observed during the larvae feeding period. Mean larvae developmental period was 17 days at 80°F. and 23 days at 70°F. when larvae were reared on sweet potatoes. Pupation occurred within a pupal cell near the soil surface and the pupal period lasted 7 to 9 days at temperatures of 70°F. and 80°F.
In 1964 Cuthbert (15) eva.luated 48 varieties and breeding lines of sweet potatoes in the field and laboratory for resistance to insect injury to roots. In field plots L3-64 exhibited a high degree of resistance to all of the injurious insect pests present. This cultivar did not sustain economic injury under conditions that commercial varie ties and breeding lines sustained damage. When laboratory ratings were correlated with field ratings, it was found that 13-64 was the most resistant cultivar in the field and the-second most resistant one in the laboratory.
Cuthbert e_t al_. (17) in cooperation with the Louisiana and
South Carolina experiment stations investigated the resistance of sweet potato cultivars to a complex of 15 insect pests. They found that 15 ofrthe 48 cultivars studied were damaged to the extent that they were unsaleable. Roots from only 8 cultivars suffered less than
50 percent damage; 6 lines had less than 45 percent; and roots from
L3-64 had only 21 percent injury.
Cuthbert and Reid (16) reported on sweet potato root injury by a species of white grub, Plectris aliena Chapin; Systena frontalis F; an anthicid, Notoxus calcaratus Horn; and a heretofore unrecognized type of the sweet potato flea beetle, Chaetocnema confinis Crotch.
It was observed in laboratory feeding studies that the larvae of the four insects fed ori sweet potato roots. 19
Cuthbert (18) states that at least. 18 species of insects feed on the edible roots of sweet potatoes. The crop grows during the year when most insect populations are the highest and their growth develop ment the most rapid. The roots were attacked from the time they began to enlarge in June until they were harvested in October and November.
The author attempts to provide growers and agricultural workers with descriptions of the insects, the degree and extent of injury they cause to sweet potatoes, pertinent information of their importance in causing crop injury, distribution, seasonal history, and habits of feeding and growth.
Cuthbert (19) found the mermithid, Fi1ipjevlmermis leipsandra
Poinar and Welch, parasitizing soil inhabiting larvae of several
Chrysomelids at Charleston, South Carolina. Although only females were found, they were able to reproduce parthenogenetically. The nematode life cycle in laboratory cages ranged from 65 to 70 days.
Larvae of the banded cucumber beetles that were parasitized ranged from 33 to 100 percent depending on the period the larvae were placed in the field. MATERIALS AND METHODS
A series of experiments were conducted from 1964 through 1966 to study resistance of fleshy roots of sweet potato cultivars to injury by larvae of the banded cucumber beetle and certain other insects under field conditions. In 1964 the effect of mulches as a means of reducing injury to sweet potato storage roots by certain soil insects was investigated and in the same year an attempt was made to develop a suitable laboratory technique for screening sweet potato cultivars for resistance to larvae of the banded cucumber beetle. A controlled greenhouse feeding study was also initiated in
1964 and completed in 1965. A genetic study of resistance of seed lings from controlled crosses was conducted in 1965.
Field Evaluations of Cultivars
Studies were conducted under field conditions from 1964 through
1966 in numerous locations in Louisiana, using a large number of sweet potato cultivars to evaluate their resistance to soil insects. A randomized block design, using four replications, was used at each location to measure differences among the cultivars. In each test 25 plants per replication were spaced 12 inches apart and planted 4 inches deep on rows four feet wide. Centennial and L3-64 were used as the susceptible and resistant standards for comparison, respe.cti.vely.
Fertilizer was applied at the rate of 400 to 600 pounds of 6-12-6 per acre or its equivalent, two weeks prior to transplanting. One-half pint of water was used around each plant immediately after transplanting. 21
No insecticides were applied to the soil or to any of the plant material used in these tests. The growing season for all experiments was approximately 120 days. Cultivation practices in the test plots were the same as those used by the grower. One harvest was made for each test and 25 roots were taken at random in each of four replications from each treatment and bagged separately. They were then brought to the Department of Horticulture, washed, and indexed for damage caused by the larvae of the banded cucumber beetle, Diabrotica balteata, Lee. and certain other soil insects including wireworm, Conoderus spp.; pale-striped flea beetle, 5ysteua blanda, Melsh; sweet potato flea beetle, Chaetocnema conflnis, Crotch; sweet potato weevil, Cyc'las formicarius elegantulus, Sum. Severity indices were calculated by the foi'mula employed by Kantack and Martin (39) and the formula was as follows:
Severity index= Summation of (No. of roots in each class x class No.)__ No. of classes - 1 x No. of roots classed
0 = no injury; 1 = 1 feeding injury; 2 = 2 to 5 feeding injuries; 3 =
6 to 10 feeding injuries; 4 = 11 to 20 feeding injuries; and 5 = over
20 feeding injuries per root.
A statistical analysis was conducted on the severity indices of each test. The higher the severity index, the greater the injury to the fleshy roots.
Mulch Studies
Black, clear and white polyethylene as well as an asphalt emul sion spray were used as mulches to provide protective coverings on the soil in four locations in 1964. An unmulched check plot served as the standard of comparison. Plastic films 36 inches wide and 2 mils in 22 thickness were used. They were applied with the aid of an applica tor designed by the Louisiana State University Agricultural
Engineering Department leaving a mulched band approximately 18 inches wide. The petroleum resin emulsion spray was applied approximately 1/8 inch thick on an 18-inch band across the tops of the rows with a piston type sprayer.
Treatments were applied to well-prepared, pre-shaped, four-foot wide seed beds containing 400 to 600 pounds per acre of a 6-12-6 fertilizer. Each experiment consisted of a randomized block design using whole row plots approximately 200 feet in length, and four replications to measure the response of sweet potatoes under mulches to soil insects. Centennial, Goldrush, Unit I Porto Rico, and L4-89 were the cultivars used in the mulch experiments. Sweet potato plants were transplanted through the plastic and petroleum mulches. Plants within the row were spaced 12 inches apart and planted four inches deep. Each plant received one-half pint of water immediately after transplanting. After planting was completed in each test, the exposed soil in the middle of rows was treated with the pre-emergence herbi cide diphenamid (N,N-dimethyl-2,2-dimethylacetamide) to control annual grasses and weeds. No insecticides were applied to the soil or to plant material in these experiments. Each test was harvested after approximately a 120 day growing season. A random sample consisting of
25 roots was collected from each of four replications in each treat ment and bagged separately. The samples were then taken to the
Department of Horticulture and washed and dried. They were then indexed for banded cucumber beetle larvae damage and other insect injury according to the formula used by Kantack and Martin (39). 23
Feeding Studies
Controlled feeding studies were initiated in 1964 in an effort
to find a suitable laboratory technique for screening sweet potato
cultivars for resistance to larvae of the banded cucumber beetle.
Two tests were conducted; the first consisting of 14 of the more
advanced cultivars, including Centennial as a susceptible, and L3-64
as a resistant standard of comparison. Storage roots of each cultivar were harvested, washed, and dried on August 5, 1.964, and subsequently
labeled with a permanent type marking pencil. The roots v/ere then
placed in a 3 x 4 foot flat with a 1 1/2 inch thickness of soil where
corn had been previously planted. The tops of young corn seedlings were removed, leaving only the roots of the corn plants. Roots of
each cultivar tested were replicated four times in separate flats with
each flat being a replicate. They were then covered with two inches of damp peat moss. Two thousand banded cucumber beetle larvae in the
first and second instars were introduced into each flat immediately
following the covering of the roots by placing them on the surface of
the peat moss. The flats containing the fleshy roots were covered with a cage made of 32 x 32 mesh screen to prevent the entry of other
insects. They were then placed into a room at the John M. Parker
Agricultural Center at a temperature of approximately 80°F. The flats were watered as needed to maintain sufficient moisture for survival of
the larvae. After 18 days of larvae feeding on the fleshy sweet potato roots, the roots were removed from the cages on August 24, 1964., and
indexed for injury caused by the banded cucumber beetle larvae. The
injury on the roots was classified into small, medium, and large holes.
Data were statistically analyzed to measure differences among cultivars. 24
The second controlled feeding study was started on September 18, 1964 and consisted of a total of 117 cultivars. In this test no corn seedlings were previously grown in the bedding media but feeding time was the same as in the first test.
Greenhouse Feeding Study
In October of 1964, a soil mixture consisting of 50 percent peat moss and 50 percent Lintonia silt loam soil was mixed as media for a controlled greenhouse sweet potato feeding study. Agricultural lime stone equivalent to 4 tons per acre was added to the media to maintain a soil pH of approximately 5.5. Fertilizer at the rate of 500 pounds of 3-12-12 per acre was added to the soil. The soil was placed in
4 x 20 foot benches one foot deep and sterilized with methyl bromide at a rate of one pound per 100 square feet of area. Plants of 41 cultivars used in the sweet potato breeding program at Louisiana State
University were transplanted into each of four benches; one plant of each cultivar was planted into each bench representing one replication.
The growing area of each plant was approximately two square feet. The greenhouse feeding study was continued in 1965. Plants were watered as needed to maintain sufficient moisture for proper growth and development. First and second instar larvae of the banded cucumber beetle were introduced into each bench of sweet potatoes on March 20,
March 21, April 16, April 17, and May 14, and the number of larvae per bench on each date were 250, 125, 75, 50, and 125, respectively. In addition, 165 adult banded cucumber beetles with clipped wings were introduced into each bench on May 27, 1965. Fleshy roots were harvested 25 on July 20, 1965, and severity indices were calculated using the same procedure as for those harvested from field plots.
Genetic Study
True seed of sweet potatoes were planted in greenhouse benches on January 15, 1965, at the Louisiana State University Sweet Potato
Research Center, Chase, Louisiana, in a mixture of 50 percent peat moss and 50 percent sterilized silt loam soil. Seedlings were allowed to grow until May 1, 1965, when they had small fleshy roots approxi mately one inch in diameter. Plants were then transplanted to the field on a row four feet wide and spaced three feet apart within the row. They were allowed to grow for approximately 45 days at which time five to ten vine cuttings were obtained from each seedling and brought to the Louisiana State University Ben Hur Farm and planted.
After a growing season of approximately 120 days the roots were harvested and indexed for injury caused by the banded cucumber beetle larvae. Severity indices were calculated by the same method discussed earlier. RESULTS
A series of experiments was conducted from 1964 to 1966 to evaluate sweet potato cultivars for resistance to larvae of the banded cucumber beetle. These data are presented in Tables 1 through
19. In addition, data relative to pale-striped flea beetle larvae injury to fleshy roots are presented in Table 20; wireworm and surface miniixg injury in Tables 21, 22, and 23; sweet potato flea beetle injury in Table 24; grub injury in Table 25; and sweet potato weevil injury in Table 26.
Results of mulching experiments in 1964 are shown in Tables 27 through 30.
Data from controlled feeding studies in 1964 and 1965 are pre sented in Tables 31 and 32.
Data from genetic studies in 1965 are shown in Table 33 and
Figure 1.
Field Evaluation of Cultivars
Banded Cucumber Beetle
Fifty-one cultivars were tested at Levisburg, La. in order to determine their resistance to banded cucumber beetle larvae. These results are shown in Table 1. Although differences could not be shown statistically, severity indices ranged from 0-35 to 22.45. The sever ity index of L3-64, the resistant check, was only 1,70, however, seven other cultivars were injured less severely. Centennial was used as the susceptible check, and had a severity index of 4.85. There were 23 cultivars with an injury rating lower than Centennial and 27 were higher..
26 The data obtained from an experiment conducted in Baton Rouge are presented i.n Table 2. Seventeen cultivars were used in this experiment and the results showed that roots of L8-67 were the least
injured by larvae of the banded cucumber beetle. The index ratings ranged from a low of 2.03 for L8-67 to a high of 49.95 for E-1097-57.
Cultivars L8-67, L3-64, L9-39, and 1,4-89 had index ratings that ranged
from 2.03 to 11.63. The injury rating for L8-67 was significantly
lower at the .05 level than 12 other cultivars. However, no statis tical differences were found among L8-67, 13-64, L9-39, L4-89 and
L9-66. Their index ratings were, significantly lower than Centennial at the .05 level and L8-67, L3-64, and L9-39 were lower than Centennial at the .01 level of significance. Cultivars L9-89, V-2158, M-O-36-2, and E-1097-57 had higher index ratings than Centennial although the differences were noc significant with the exception of E-1097-57, which was significantly higher.
There were 10 cultivars tested for resistance to the banded cucumber beetle at Scott, La. and data from this test are shown in
Table 3. There were no statistical differences among the cultivars.
The least affected cultivar was Goldrush with a severity index of
11.70 and a severity index rating of 20.05 for L2-192 was the highest.
Centennial ranked fourth with an index of 13.15.
Twelve cultivars were grown and evaluated for resistance to injury by banded cucumber beetle larvae at Arnaudville, La. The severity index readings of the cultivars ranged from 0.10 to 10.30 and are shown in Table 4. Ten of the cultivars had significantly lower indices than Centennial and Goldrush, and nine were significantly lower 28 at the .01 level of significance. Cultivars NC-210, L3-64, Nugget, and L9-125 had low index ratings ranging from 0.10 to 1.40.
There were 11 cultivars tested for resistance to banded cucumber beetle larvae injury at Baton Rouge, La. and the data are shown in
Table 5. The severity indices ranged from a low of 13.6 for Ll-111 to a high of 52.2 for Centennial. Due. to the large amount of varia tion among replications for the same cultivar, the differences among cultivars were not significant.
Data from an experiment with 13 cultivars at Scott, La. in 1965 are presented in Table 6. No significant differences were found among cultivars in this test. Four cultivars showed less injury to fleshy roots than L3-64 which had a severity index of 18.6. Centennial had a severity index of 37.4.
In a test at Baton Rouge, La. there were 45 cultivars grown and the severity index of the fleshy roots injured by larvae of the banded cucumber beetle ranged from a low of 0.4 for L3-64, L3-227, and L3-127 to a high of 15.4 for L3-37. As shown in Table 7, no significant dif ferences were found among cultivars.
Data from an experiment with 19 culti.vars in Arnaudville, La. are shown in Table 8. Results showed that fleshy root injury by larvae of the banded cucumber beetle ranged from a low of 2.4 for L8-67 to a high of 13.7 for Centennial-8. The index readings for L8-67 and L3-64 were significantly lower than Ll-111, Centennial-2, and Centennial-8.
Centennial fleshy roots had an index of 8.1 and did not differ signifi cantly from any of the other cultivars.
Data obtained from 13 cultivars in an experiment at Kidderville,
La. are shown in Table 9. No significant differences relative to 29 banded cucumber beetle iivjury to the fleshy roots were obtained among cultivars. The index ratings ranged from a low of 0.40 for L8-67 to a high of 6.83 for Centennial. L3-64 had an index rating of 0.80.
Twenty cultivars were tested at Ville Platte, La. in an effort to determine the most resistant to banded cucumber beetle, larvae.
As shown in Table 10 severity indices were rather low. Centennial-5 and LO-241 were injured significantly less at the .05 level than
Centennial, Ll-193, Centennial-2, and Julian. Although L3-64 had an index 0.8, five other cultivars were injured even less. Only three cultivars were injured more than Centennial.
An experiment was conducted in Grand Coteau, La. to study the resistance of 16 culti.vars to larvae of the banded cucumber beetle and results are shown in Table 11. Injury indices ranged from 0.0 for
L2-185 to a reading of 5.2 for L0-189. L3-64 and L2-196 had a severity index of 0.7. Twelve cultivars showed less injury than Centennial.
At Hessmer, La. 15 cultivars were tested and the results are shown in Table 12. Centennial-1, L3--64, Ll-93 and L2-74 were not injured at all and the most severely injured cultivar was LO-189 with a reading of 2.3. Centennial ranked tenth with an index of 0.8.
Eighteen cultivars were tested at Clinton, La. and the results are presented in Table 13. Results showed that L3-64 was the most resistant cultivar with a severity index of 15.0 and Julian was the most susceptible cultivar with a rating of 64.8. L3-64 was the only cultivar to sustain significantly less injury than Centennial at the
.05 level.. The injury measured on L3-64 v/as also significantly lower at the .05 level than the injury on 11 other cultivars in this test.
Centennial ranked thirteenth with an index of 45.3. Twelve cultivars were tested for resistance to larvae of the banded cucumber beetle at Baton Rouge, La. The severity indices of these ranged from a low of 6.2 for Coastal Sweet to a high of 22.2 for
Centennial-2 and these data are presented in Table 14. Coastal Sweet,
L9-89 and Ll-93 had significantly less injury to the fleshy roots than
Goldrush, LQ-189 and Centennial-2. LO-189 and Centennial-2 had sig-- nificantly more injury than all cultivars in the test with the excep tion of Goldrush. Coastal Sweet, L9-89, Ll-93, Centennial~T, and
Julian were also injured significantly less than LO-189 and Centennial-
2 at the .01 level of significance. Centennial, had a severity index of 10.6.
In an experiment at St. Gabriel, La. 20 cultivars were evaluated for resistaiT.ee to larvae of the banded cucumber beetle and the results are shown in Table 15. The. severity indices ranged from a low of 2.7 for L3-64 to a high of 43.4 for Rose Goldrush. Roots of L3-64, L2-175,
L2-185, and LO-241 were injured significantly less than those of
Centennial. Also, roots of L3--64 and L2-175 suffered significantly less damage at the .01 level of significance. L3-64 was injured signi ficantly less than the 16 other cultivars in the test. Centennial had a severity index rating of 33.4.
At Baton Rouge, La. 20 cultivars were tested for resistance to the banded cucumber beetle. Results of this experiment are shown in
Table 16. The severity indices ranged from a low of 3.6 for L3-64 to a high of 45.8 for L'l-193. Fleshy roots of L3-64, LO-241, L0-132,
L2-185, L0-246 and Unit I Porto Rico were injured significantly less
than Centennial 'which had a severity rating of 28.8. L3-64 and LO-241 were injured less than Centennial at the .01 level of significance. 31
Mean severity indices of injury to fleshy sweet potato roots by the banded cucumber beetle larvae for 10 experiments are shown in
Table 17. The mean severity index of L3-64 was 4.5 and it was highly resistant. A number of other cultivars showed a high degree of resistance; however, these were not planted at all locations.
Cultivars showing considerable resistance when tested in several loca tions were Ll-128, L9-89, LO-241 and L2-185. The mean severity indices of these cultivars ranged from 5.8 through 7.9. Mean severity indices were the results of three to nine field tests. These data showed cultivars L2-175, L4-89, Centennial-4, Centennial-8, and L9-39 to be moderately resistant to injury by the banded cucumber beetle. Based on results of from three to nine tests, Ll-111, Ll-93, L0-132, LO-246,
L2-96, Centennial-5, L8-67, L2-167, LO-189, Pelican Processor, and
L2-116 were susceptible with an index irating ranging from 12.0 to 17.3.
Cultivars that showed a high degree of susceptibility when evaluated at four to 12 locations included Goldrush, Ll-193, Centennial, Unit I
Porto Rico, Julian, and Centennial-2. The severity indices of these cultivars ranged from 18.8 to 22.3. Higher indices were recorded for
L9-66, NC-210, L2-66, Rose Goldrush, B-7078, NC-215, and L9-143, with a high of 56.8.
The data presented from five locations in Table 18 for 1966 show the mean percentage of roots of cultivars injured by banded cucumber beetle larvae which ranged from 7.4 percent for L3-64 to 54.5 for
L3-179. Twenty-one and seven-tenths percent of Centennial roots were injured. As an average of all locations 13 cultivars had less roots injured than Centennial. L3-64 had fewer root injuries at all loca tions with the exception of Scott, La. where it was in a low injury group with L2-116, LJ-2.2.1 and Rose Centennial. 32
Sixteen cultivars were tested at St. Gabriel, La. with percentage of roots injured ranging from 1.9 for L3-64 to 76.0 for L0-246. Fleshy roots of eight cultivars had a significantly greater percentage of injury than L3-64. Six of these cultivars were injured more than
L3-64 at the .01 level of significance. Only LO-246 was injured more than Centennial at the .05 level of significance.
Data from an experiment at Hessmer, La. using 12 cultivars showed percentage of roots injured ranging from 10.7 for L3-64 to 54.5 for L3-179. Roots of seven cultivars had a significantly greater per centage of root injury than L3-64. Although no statistical difference was measured between L3-64 and Centennial, only one cultivar had signi ficantly more roots injuied than Centennial.
At Ville Platte, I,a, 14 cultivars were tested and the percentages of roots injured were low and no differences among cultivars could be shown statistically.
The data obtained at Scott, La. showed that roots of L2-116 had the lowest percentage of injury with 13.0 percent and 7.,0-246 the highest with 48.9 percent. All cultivars had statistically fewer roots injured than LO-246 with the. exception of L3-217. No statistical dif ferences were found among cultivars L2-116, L3-66, Rose Centennial,
1,3-64, Ll-35, Ll-193, and L3-39. L2-116 had statistically fewer roots injured than Centennial.
Results from another field test at Clinton, La. with 13 cultivars showed that no cultivars were statistically different from Centennial with regard to injury. I..3-64, Ll-35, and Centennial-2 had significantly fewer injured roots than Centennial. Cultivars L3-64, LO-132, and
Centennial-2. had a significantly lower number of roots injured by 33 banded cucumber beetle larvae than Centennial-1, L3-217, Centennial,
and L2-61.
Data presented in Table 19 as a mean of five locations showed
that fleshy roots of L3-64 were the least severely injured by banded
cucumber beetle larvae with a severity index reading of 2.9 and L3-179 was the most severely injured with a severity index of 32.7. The mean
severity indices of 21 cultivars are presented in this table and
Centennial ranked thirteenth with a severity index of 9.5.
Sixteen cultivars tested at St. Gabriel, La. had a severity
index range of 0.7 for L3-64 to 48.0 for L0-246. Roots of L3-64 and
L3-221 sustained significantly less injury than Centennial, Ll-35,
and L0-246. In addition to these, L3-64 suffered significantly less
root injury than Centennial-8. Both L3-64 and L3-221 were injured
less severely than Ll-35 a.r>d LO-246 at the .01 level of significance.
At Hessmer, La. 12 cultivars were evaluated and the severity
indices ranged from 4.5 for L3-64 to 32.7 for L3-179. Highly signifi
cant differences were obtained among the cultivars in this experiment. -
L3-64 had the lowest index reading but it was not significantly differ
ent from Centennial. However, L3-64 had a significantly lower severity
index than L2-61, Julian, L3-221, Ll-193, LO-132, L3-217, and L3-179
and it was significantly lower than LO-132, L3-217, and L3-179 at the
.01 level of significance.
The severity indices for root injury on 14 cultivars at Ville
Platte, La. were very low and no significant differences among these
cultivars were observed.
Fourteen cultivars were grown at Scott, La. and severity indices
for banded cucumber beetle injury ranged from a low of 5.2 for 1.2-116 34 to a high of 22.6 for LO-246. Centennial had a severity index of 11.4 which was approximately 100 percent greater than L2-116, but this dif ference was not significant. LO-246 had a severity index of 22.6 and this value was significantly larger than Centennial at the .01 level.
No cultivar had fleshy roots with significantly less injury than L3-64.
Data from a test at Clinton, La. with 13 cultivars showed severity indices that ranged from 1.8 for L3-64 to 9.1 for Centennial. The severity index for root injury on L3-64 was significantly lower than
Centennial, L2-61, L3-217, and Centennial-1. Both Centennial-2 and
L3-39 had lower indices than Centennial at the .05 level of signifi cance .
Pale-striped Flea Beetle
Data obtained on severity indices of injury to fleshy roots of cultivars by pale-striped flea beetle larvae from five locations in
1966 are shown in Table 20. Mean severity indices of 21 cultivars ranged from 5.9 for Centennial-8 to 32.0 for LO-246. L3-64 was evaluated at five locations and it had the lowest severity index of
7.2. Three other cultivars, Centennial-8, L9-39, and Centennial-4 had severity indices of 5.9, 7.0 and 7.0, respectively, but each was tested at only one location.
An experiment at St. Gabriel, La. included 16 cultivars and both
L3-64 and L3-217 showed no injury by larvae of the pale-striped flea beetle. All cultivars included in this test had lower indices than
LO-246 at the .01 level of significance. L3-64, L3-217, and L3-66 had significantly lower severity indices than Julian and Ll-35.
Twelve cultivars were grown at hessmer, La. and evaluated for resistance to che pale-striped flea beetle larvae. Although no 35
significant differences among cultivars were shown, the severity indices ranged from 2.8 for L3-64 to 18.5 for LO-132. Centennial had an index of 6.6.
The severity of injury to fleshy roots by the pale-striped flea beetle larvae on 14 cultivars tested at Ville Platte, La. was extremely low. The highest severity index was only 1.3. This indicated that a low infestation of flea beetles occurred in this test.
Data from an experiment at Scott, La. showed that pale-striped
flea beetle injury to fleshy sweet potato roots was severe. Fourteen cultivars were tested at this location and severity indices ranged from
24.2 for L3-5 to 52.1 for L3-66. There were, however, no statistically
significant differences among cultivars.
At Clinton, La. 13 cultivars were tested and the severity indices of the roots ranged from 7.0 for L9-39 to 42.3 for LO-132. No cultivars had significantly lower indices than Centennial. The severity index of L3-64 was significantly lower than L3-217, Ll-193, L2-61, Centennial-
2, Centennial-1, Julian and LO-132.
Wireworm and Surface Mining
Data in Table 21 show the percentage of roots of cultivars
injured by wireworms at each of five locations and the mean percentage of injury from all locations. The mean percent injury of fleshy roots
ranged from a low of 3„7 for L3-64 to a high of 56.5 for L3-179.
Data from a test at St. Gabriel, La. where 16 cultivars were grown showed that the percentage of fleshy roots injured by wireworms ranged from zero for L3-64 to 59.5 percent for LO-246. L3-64, L3-217,
L3-221, L2-U6, L3--66 and L2-61 had significantly less root injury than 36
Centennial and L3-64, L3-217, L3-221, L2-116 and L3-66 had less injury than Centennial at the .01 level of significance. Only LO-246 was injured significantly more than Centennial and this difference was significant at the .01 level.
Data obtained from a test at Hessmer, La. with 12 cultivars showed a range of wireworm root injury from 5.8 percent for L3-64 to
56.5 percent for L3-179. No cultivar had a significantly smaller percentage of root injury than Centennial. Julian and L3-179 were the only two cultivars with significantly more injury than Centennial.
Seven cultivars had a significantly higher percentage of root injury than L3-64 and five of these had significantly more injury at the .01 level of significance.
At Ville Platte, La. 14 cultivars were tested for wireworm injury and results showed that seven of the cultivars were free of injury and the other seven suffered only minor injury ranging from 1.3 percent of the roots injured to a high of 4.9 percent.
At Scott, La. 14 cultivars were evaluated and the percentage of fleshy roots injured ranged from 4.1 percent for L3-66 to 43.9 percent, for LO-246. L3-66 was the only cultivar with significantly less injury than Centennial which had 21.8 percent of roots damaged. LO-246 had a significantly higher percentage of root injury than Centennial.
Data from an experiment at Clinton, La. using 13 cultivars showed a range of root injury from 2.1 percent', for L3-64 to 38.5 percent for Julian. No cultivar was injured significantly less than Centennial although four cultivars did have a smaller percentage of roots injured.
Fleshy roots of Centennial sustained significantly less injury than 37
L3-217, LI-193, and Julian. The percentage of L3-64 roots injured were significantly less than six other cultivars and less than four
cultivars at the .01 level of significance.
Data in Table 22 show the percentage of roots of cultivars
injured at each of five locations from surface mining and the mean percentage _of injury of all locations. There were no damaged roots
for Centennial-8, Centennial-4, and L3-179 when tested at one location.
LO-246 had the highest injury with 11.1 percent of the roots injured
as an average of all locations.
Results from a test at St. Gabriel, La. showed that no roots of
any of the cultivars were affected with surface, mining injury.
Data from a test at Hessmer, La. showed that only five of the
12 cultivars had root injury. Roots of Julian sustained the greatest
percentage of injury with 3.1 percent, followed by L3-39 with 2.4
percent, and L3-221, Ll-193, and Ll-35 with 1.0 percent.
Data from a test at Ville Platte, La. showed that a low per
centage of fleshy roots of seven cultivars were injured by surface mining. Ll-35 was the most severely injured cultivar with only 5.4
percent root damage, but this injury was significantly higher than
that of other cultivars at the .01 level of significance with the
exception of L3-5 where it was only significantly higher at the .05
level.
At Scott, La. 14 cultivars were tested and the range of roots
injured was from zero for 1,3-64 and LO-132 to 14.6 for LO-246. No
significant differences could be measured among the cultivars and
Centennial had 5.3 percent of the roots damaged by surface mining. 38
Data collected from an experiment at Clinton, La. on 13 culti- vars showed that significant differences in surface mining injury to
the roots occurred among cultivars. One percent of the fleshy roots
of L3-64 and L2-61 were injured and 18.6 percent of LO-246 were
damaged. All cultivars except L9-39 were injured less than Julian,
Ll-193, and LO-246 at the .01 level of significance.
Data are shown in Table 23 for percentage of roots injured by wireworm and surface mining soil insects. Fleshy roots injured by wireworm ranged from 8.0 percent for L2-185 to a high of 75.0 percent
for Goldrush. Only 8.1 percent of L3-64 roots were injured by wire worm as compared to 30.0 percent of the roots of Centennial. Roots
of most cultivars were injured little if any from surface mining.
Fifteen percent of the roots of Whitestar were damaged, 9.0 percent
of Goldrush, 6.0 percent of L2-185, 5.0 percent of Julian and LO-246,
3.0 percent of Pelican Processor and L9-89, and 2.0 percent of
LO-132, L0-241, L9-89, and LO-189. Other cultivars in the test had
no surface mining injury.
Sweet Potato Flea Beetle
Data presented in Table 24 are the results of experiments from
five locations showing percentages of root injury by sweet potato flea
beetle larvae for cultivars at each location and the mean for all
locations. Twenty-one cultivars were tested and the. mean percentage
of root injury ranged from 1.3 percent for L3-64 to 19.2 for
Centennial-1. Eleven cultivars had less injury than Centennial which
had 7.6 percent of the roots injured. No injury was recorded for
L3-64 at four of the five test locations. 39
Sixteen cultivars were evaluated at. St.-Gabriel, La. and per centage of roots injured ranged from zero for L3-64 and L2-116 to
29.0 percent for LO-246. L3-64, L2-116, Rose Centennial, and
Centennial-8 had significantly less fleshy roots injured than
Centennial and L3-64, 1,2-116 and Rose Centennial had less injury at the .01 level of significance. Three cultivars, Julian, Ll-35, and
LO-246 had a greater percentage of root injury than Centennial and root injury to LO-246 was significantly greater at the .01 level.
Results from 12 cultivars in a field test at Hessmer, La. showed that the percentage of roots injured by flea beetle larvae ranged from zero for L3-64 to 11.1 for L3-221. The percentage of roots damaged at this location was rather low and Centennial had only 1.7 percent of the roots injured.
At Ville Platte, La. 14 cultivars were tested for flea beetle larvae injury and only four cultivars sustained any injury. They were
Centennial, with 2.2 percent, Julian with 1.1 percent, and Centennial-
2 and Ll-35 with 1.0 percent fleshy root injury.
Thirteen cultivars were tested at Scott, La. and ranged in per centage of roots injured from 2.7 for L3-66 to 20.9 for L2-61.
Thirteen percent of the roots of Centennial were injured and only
two other cultivars, Ll-35 and L2-61, had a greater percentage of
fleshy roots injured. L3--64 had the second lowest root injury with
6.3 percent.
Data obtained at Clinton, La. from a test with 13 cultivars
showed a range of flea beetle root injury from zero for L3-64 to a high of 29.5 percent: for L3-217. No cultivar had a significantly
lower roof injury than Centennial, however, Centennial had a 40 significantly lower percentage of roots injured than-Ll-193, Julian, and L3-217. Roots of L3-64, Gentennial-2, L2-116, L3-39, Centennial,
LO-132, L2-61, and 10-246 had significantly less injury than Ll-193,
Julian, and L3-217. Also, L3-64 had significantly fewer roots injured at the .01 level than Ll-193, Julian and L3-217.
Grubs
The data on cultivars grown at five locations are presented in
Table 25. The mean percentages of root injury of all locations by grubs ranged from zero for L3-64 to 17.0 for LO-246. In general, most of the cultivars tested had only a small percentage of root injury.
Data from an experiment at St. Gabriel, La. where 16 cultivars were tested showed a range of root injury from zero for L3-64 and
L3-217 to 41.5 for LO-246. Roots of L3-221 and LO-246 were injured significantly more than all other cultivars in this test. Root injury to Centennial was 10.7 percent.
Results from data collected in Hessmer, La. showed that fleshy roots of only three of the 12 cultivars tested were injured by grubs.
Ll-193 had 3.9 percent root injury and LO-132 and L3-221 had 1.1 percent injury.
Data obtained from an experiment in Ville Platte, La. showed only minor injury to nine of the 14 cultivars tested. Centennial was the most severely affected with 5.0 percent root injury.
Fourteen cultivars were evaluated in a test at Scott, La. and roots of four cultivars were injured. L3-221, LO-246, L3-5, and
L3-39 had 6.5, 4.2, 2.6, and 1.3 percent root injury, respectively. 41
At Clinton, La. 13 cultivars ranged in percent of fleshy root injury by grubs from zero for L3-39 to 7.2 for Ll-193. In this test, only 1.0 percent of Centennial roots were injured compared to 2.8 percent for L3-64.
Sweet Potato Weevil
As shown in Table 26, data from an experiment at Scott, La. showed that cultivars differed in the amount of injury to fleshy roots by '"he sweet potato weevil. Roots of five of the 14 cultivars tested were free of injury. Only 1.3 percent of L3-64 roots were damaged and 4.8 percent of Centennial. The highest percentage of root injury was from cultivar Ll-35.
Mulch Studies
An experiment was conducted at Scott, La. using non-mulched and black plastic mulch treatments with Unit I porto Rico and L4-89 to test the protective effect of mulches against injury to fleshy roots by the banded cucumber beetle larvae. As shown in Table 27, there were no significant differences between mulched and non-mulched treatments with either cultivar. The severity index of Unit I Porto
Rico non-mulched treatment was 8.2 and 12.7 with the mulch. The severity index for L4-89 non-mulch treatment was 12.2 as compared to
8.6 with plastic mulch.
As shown in Table 28, large differences were measured between cultivars in a test at Church Point, La. where Goldrush and L4-89 were planted with and without black plastic mulches. The severity index of
Goldrush in the non-mulch treatment was 33.06 and in the mulch treatment 42 it was 34.57. The severity index of L4-89 was 12.70 in the non-mulch treatment and 18.07 in the mulch treatment. Differences in injury by the banded cucumber beetle larvae were the result of cultivars rather than treatments, L4-89 being more resistant to the banded cucumber beetle larvae.
Significant differences between cultivars were found in a mulch ing experiment at Lewisburg, La. and data are shown in Table 29.
Roots of L4-89 were injured significantly less than Centennial by the banded cucumber beetle larvae at the .01 level of significance. The severity index of L4-89 was 1.1 in the non-mulch treatment and 1.6 in the mulch treatment. The severity index of Centennial roots in the non-mulch treatment was 8.8 and 7.2. in the mulch treatment.
Four different mulches were used in an experiment at Baton Rouge,
La. to evaluate their effectiveness in controlling banded cucumber beetle larvae in Centennial sweet potatoes and results are presented in Table 30. Severity indices for treatments were as follows: non- mulched 1.17; clear plastic 1.57; white plastic 2.10; asphalt spray
3.00, and black plastic 5.43. There were no significant differences among mulch treatments.
Feeding Studies
An experiment was conducted in 1964 at Baton Rouge, La. to evaluate the resistance of 14 cultivars to injury by larvae of the banded cucumber beetle. As shown in Table 31, iiajury was measured by the mean number of small, medium, large, and total holes in each root of each cultivar. The small hole injury to fleshy roots ranged from a low of 3.5 for 1,9-125 to 26.3 for L9-66. L9-125, L4-89, and L3-64 had significantly fewer small holes than Centennial and L9--125 had less injury at the .01 level. L4-50 and L9-66 were the only two cultivars with more injury than Centennial, however, this difference was not significant. There were no significant differences in number of medium holes in roots among cultivars, although the range was from
1.3 per root for L4-89 to 9.6 for L9-66. Injury as measured by large holes was rather limited with a range from zero on L4-89 and L9-39 to
4.0 per root for L9-125. The means for total number of holes per root were from 7.6 for L4-89 to 37.9 for L9-66. Cultivars L4-89 and
L9-125 were the only two that had significantly less total holes per root than Centennial which had an average of 24.1 per fleshy root.
Centennial had fewer total punctures than L9-89, L4-50, and L9--66.
1.4-89 had fewer holes than L4-50 and L9-66 at the .01 ievel of signi ficance. All cultivars with the exception of Centennial, L9-89, and
L4-50 had significantly fewer holes per root than L9-66 at: the .05 level of significance.
No data were recorded for the second feeding study on freshly harvested fleshy roots. All banded cucumber beetle larvae died before sweet potato root injury occurred.
Forty-one cultivars were evaluated for resistance to banded cucumber beetle larvae in a greenhouse experiment in 1964 and 1965.
As shown in Table 32, the severity indices ranged from 3.33 for Jersey
Orange, to 36.30 for Centennial. However, no statistical differences could be measured. L3-64 ranked tenth and in general those with L3-64 parentage showed less injury when compared with other cultivars. 44
Genetic Studies
There were 177 seedlings obtained from a controlled cross of
L3-64 x Nemagold, two moderately resistant parents, to study the mode of inheritance of resistance to the banded cucumber beetle larvae.
The severity indices and the number of fleshy roots evaluated for each seedling are shown in. Table 33. The distribution of the severity indices of the seedlings into different resistant classes is shown in Figure 1. The severity indices for L3-64, Nemagold, and
Centennial are also shown in Table 33.
As shown in Figure 1, the distribution of seedlings was skewed toward resistance. There were a total of 45.2 percent of the seedlings that were very resistant to resistant to the banded cucumber beetle larvae. Tnese seedlings had a range in severity indices from 0.0 to
5.0. The severity indices for L3-64 and Nemagold were 6.8 and 9.4, respectively. Centennial, a susceptible cultivar, had a severity index of 37.5. There were 22.6 percent of the seedlings found to be moder ately resistant or as resistant as the two parents with severity indices ranging from 5.1 through 10.0. There were 17.5 percent of the seedlings in the moderately susceptible class having severity indices that ranged from 10.1 to 15.0. In the susceptible and very susceptible classes there was a total of 14.7 percent of the seedlings that had severity indices ranging from 15.1 through 38.3.
Resistance of sweet potato seedlings to banded cucumber beetle larvae is quantitative due to lack of simple mendelian expression of this character. A large number of seedlings segregated for resistance to moderate resistance in the cross of L3-64 x Nemagold as shown in
Figure 1. 45
Table 1. Severity indices of sweet potato root injury by larvae of Diahroticn bal teat a on cultivars at Lev/isburg, Louisiana.
Cultivar Severity Index Cultivar Severity Index
L2-185 0.35 L2-74 5.75 Heartogold 0.80 Reg. Goldrush 6.15 L2-196 0.90 L0-156 6.55 Whitestar 1.00 L4-50 6.65 LO-281 1.05 Ll-ill 6.75 Pelican Processor 1.30 L8-67 6.80 Unit T. Porto Rico 1.40 L2-1 6.80 L3-64 1.70 LI-126 7.45 LO-132 2.05 L9-23 7.80 Ll-93 2.15 L0-253 8.00 L2-66 2.20 LO-246 8.10 LO-189 2.55 L2-61 8.55 LO-241 2.60 Centennial-4 8.60 L2-175 2.85 LI-108 8.70 Red Goldrush 2.85 L0-135 9.00 L9-39 2.85 Ll-19 9.40 L4-89 2.85 L0-269 9.65 L2-67 2.90 L8-3 9.65 Centennial-5 2.95 Ll-193 10.10 L9-89 3.00 L2-60 10.10 L9-125 3.20 Ll-128 10.45 Goldrush 3.75 L0-255 10.85 L9-66 4.60 Centennial-3 13.55 Centennial 4.85 Centennial-1 14.85 L9-143 5.40 Ll-35 22.45 L2-57 5.75
NS NS
Planted June 9, 1964; harvested Oct. 22, 1964. 46
Table 2. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at the Hill Farm, L.S.U., Baton Rouge, Louisiana.
Cultivar______Severity Index
L8-67 2.03 L3-64 5.80 L9-39 10.80 L4-89 11.63 L9-66 14.98 L8-3 18.70 Goldrush 19.40 NC-198 19.55 NC-188 21,20 NO-210 21.63 L9-125 22.05 L9-143 27.05 Centennial 29.98 L9-89 32.05 V-2158 41..65 M- 0-36-2 43.30 E-1097-57 49.95
LSD @ .05 13.82 @ .01 18.42
Planted May 18, 1964; harvested Sept. 21, 1964. 47
Table 3. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Scott, Louisiana.
Cultivar Severity Index
Goldrush 11.70 LO-132 11.90 LI-93 12.60 Centennial 13.15 L8-3 13.25 L9-125 13.60 L4-89 13.80 Centennial T 15.70 L2-1 16.30 L2-192 20.05
NS
Planted June 9, 1964; harvested Oct. 6, 1964.
Table 4. Severity indices of sv7eet potato root injury by larvae of Diabrotica balteata on cultivars at Arnaudville, Louisiana.
Cultivar Severity Index
NC-210 0.10 L3-64 0.15 Nugget 0.95 L9-125 1.40 NC-188 3.15 E-86-72 3.60 L0-189 5.95 L4-89 6.20 Centennial T 6.30 L8-3 8.70 Centennial 10.00 Goldrush 10.30
LSD @ .05 1.30 @ .01 1.75
Planted June 10, 1964; harvested Oct. 2.3, 1964. . 48
Table 5. Severity indices of sweet potato root injury by larvae of biabrotica baltcata on cultivars at the Hill Farm, L.S.U., Baton Rouge, Louisiana.
Cultivar Severity Index
Ll-111 13.6 LO-246 14.4 Julian 15.2 LO-189 21.6 Goldrush 21.6 LO-132 24.8 NC-210 28.8 Ll-193 33.6 B-7078 41.6 NC-215 45.6 Centennial 52.2.
NS
Planted May 17, 1965; harvested Oct. 7, 1965.
Table 6. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Scott, Louisiana.
Cultivar Severity Index
LO-241 8.8 LO-132 10.4 Ll-93 17.0 LI-128 17.2 L3-64 18.6 L2-116 20.2 LO-189 25.6 L2-196 26.8 L2-66 32.6 Julian 36.4 Centennial 37.4 Unit I Porto.Rico 38.0 Centennial-2 40.8
NS
Planted June 3, 1965; harvested Oct. 14, 1965. 49
Table 7. Severity indices of sweet potato root injury by larvae of Diabrotica baltcata on cultivars at the LSU Quail Farm, Baton Rouge, Louisiana.
Cultivar Severity Index Cultivar Severity Index
L3-64 0.4 L3-15 4.4 L3-227 0.4 L3-130 4.7 L3-127 0.4 L3-151 4.7 L3-141 0.6 L3-221 4.8 L3-186 0.7 L3-217 5.3 LI-93 0.7 L3-152 5.4 L3-39 1.0 Whitestar 5.4 L3-146 1.1 L3-65 5 .6 L3-5 1.2 L2-116 5.6 L3-220 1.5 Centennial-5 6.0 L3-241 1.7 L3-143 6.2 L3-66 1,7 L3-233 6.5 L2-167 2.0 L3-197 6.8 L4-89 2.2 L2-196 7.0 Centennial 2.9 LI -128 7.1 L2-175 2.9 L3-225 7.4 L9-89 3.0 L3-252 8.2 LO-241 3.5 Julian 8.5 L3-11 3.5 L3-114 9.1 L3-36 3.6 Pelican Processor 10.3 L3-44 4.0 L3-136 14.6 Unit I Porto Rico 4.2 L3-37 15.4 Heartogold 4.3
NS NS
Planted May 28, 196.5, harvested Sept. 30, 1965. 50
Table 8. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Arnaudville, Louisiana.
Cultivar Severity Index
L8-67 2.4 L3-64 2.5 LO-132 3.8 LO-241 4.3 LO-246 5.3 Ll-128 5.4 L2-167 6.7 L4-89 7.2 LO-189 7.6 Ll-193 7.6 Centennial 8.1 Julian 8.7 L2-175 8.9 L9-89 9.1 L2-196 9.6 Centennial-4 9.8 Ll-111 13.2 Centennial-2 13.2 Centennial-8 13.7
LSD @ .05 9.5
Planted April 30, 1965; harvested Aug. 26, 1965. 51
Table 9. Severity indices of sweet potato root injury by larvae of Diabrotic.a balteata on cultivars at Kidderville, Louisiana.
Cultivar Severity Index
L8-67 0.40 LO-241 0.60 L3-64 0.80 L4-89 0.80 LO-132 0.80 L9-89 1.20 LO-189 1.60 LO-246 1.60 Ll-111 1.60 Ll-128 2.45 Ll-193 3.40 Julian 4.80 Centennial 6.83
NS
Planted April 14, 1965; harvested July 28, 1965. 52
Table 10. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Ville Platte, Louisiana.
Cultivar Severity Index
Centennial-5 0.0 LO-241 0.2 L2-185 0.4 L9-39 0.4 L9-89 C».6 LO-132 0.8 LO-246 0.8 L3-64 0.8 L8-67 1.0 Ll-111 1.2 LI-123 1.2 LO-189 2.2 L2-196 2.4 Centennial-4 2.6 L4-89 2.6 Centennial-8 2.8 Centennial 3.0 Ll-193 4.2 Centennial-2 4.6 Julian 6.4
LSD @ .05 2.8 .01 3.7
Planted May 7, 1965; harvested Sept. 1, 1965. 53
Tabic 11. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Grand Coteau, Louisiana.
Cultivar______Severity Index
L2-185 0.0 L2-196 0.7 L3-64 0.7 L8-67 1.0 L4-87 1.0 Ll-128 1.5 Centennial-8 1.6 Ll-93 1.8 Whitestar 2.0 Julian 2.3 L9-89 2.4 Pelican Processor 2.4 Centennial 2.7 Unit I Poi'to Rico 2.8 Centennial-4 3.6 LO-189 5.2 NS Planted May 10, 1965; harvested Sept. 2, 1965.
Table 12. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Hessmer, Louisiana.
Cultivar______Severity Index
Centennial-1 0.0 L3-64 0.0 Ll-93 0.0 L2-74 0.0 L4-89 0.2 L2-192 0.3 Ll-193 0.4 Centennial-2 0.4 L9-66 0.5 Centennial 0.8 LO-132 0.8 L9-39 0.8 Goldrush 1.2 LO-246 1.8 LO-189 2.3 NS
Planted May 12, 1965; harvested Sept. 24, 1965. 54
Table 13. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at Clinton, Louisiana.
Cultivar Severity Index
L3-64 15.0 L9-39 23.8 L2-192 29.3 L4-89 30.0 Ll-93 30.5 LO-132 36.3 Goldrush 36.8 Ll-193 39.5 LO-189 40.0 Centennial-2 42.8 L2-74 43.5 Centennial-1 44.8 Centennial 45.3 L8--67 48.5 L9-66 50.0 LO-246 52.3 L9-143 56.8 Julian 64.8
LSD @ .05 23.4
Planted June 17, 1965; harvested Oct. 21, 1965. 55
Table 14. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at the L.S.U. Hill Farm, Baton Rouge, Louisiana.
Cultivar Severity Index
Coastal Sweet 6.2 - L9-89 6.8 Ll-93 7.0 Centennial T 9.4 Julian 10.4 Centennial 10.6 LO-241 11.0 C56-35 (C5625) 11.3 Gem 11.4 Goldrush 15.4 LO-189 19.9 Centennial-2 22.2
LSD (§ .05 6.9 (3 .01 9.3
Planted Hay 17, 1965; harvested Oct. 7, 1965. 56
Table 15. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at St. Gabriel, Louisiana.
Cultivar Severity Index
L3-64 2.7 L2-175 12.6 L2-185 17.0 LO-241 17.7 L9-39 18.4 L8-67 18.4 L4-89 20.9 LO-132 22.7 L2-196 25.8 L2-116 26.2 Centennial-5 28.1 Ll-111 30.6 Centennial-2 31.0 LO-189 31.4 Unit I Porto Rico 31.5 Centennial 33.4 L2-167 38.7 Pelican Processor 38.8 Julian 43.2 Rose Goldrush 43.4
LSD @ .05 15.4 @ .01 20.5
Planted May 15, 1965; harvested Sept. 24, 1965. 57
Table 16. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars at L.S.U. Ben Hur Farm, Baton Rouge, Louisiana.
Cultivar Severity Index
L3-64 3.6 LO-241 11.1 LO-132 14.1 L2-185 14.3 LO-246 15.4 Unit I Porto Rico 18.1 L2-196 19.1 L9-89 21.3 Centennial-5 21.5 Centennial 22.2 L4-89 22.9 Centennial-2 23.2 Centennial-4 23.5 Julian 25.5 L8-67 26.2 LO-189 26.9 Rose Goldrush 27.9 Centennial 28.8 Ll-93 29.9 Ll-193 45.8
LSD @ .05 12.2 .01 16.2
Planted May 21, 1965; harvested Oct. 5, 1965. 58
Table 17. Mean severity indices of sweet potato root injury by larvae of Diabrotica balteata on cultivars from several locations in Louisiana, 1965.
Mean N o . of Mean No. of Cultivar Index* Tests Cultivar Index* Tests
L3-227 0.4 1 L4-89 9.8 9 L3-127 0.4 1 Centennial-4 9.9 4 L3-141 0.6 1 Centennial-8 10.1 4 L3-186 0.7 1 L9-39 10.9 4 L3-39 1.0 1 C56-35 11.3 1 L3-146 1.0 1 Gem 11.4 1 L3-5 1.2 1 Ll-111 12.0 5 L3-220 1.5 1 Ll-93 12.4 7 L3-241 1.7 1 LO-132 12.7 9 L3-66 1.7 1 LO-246 13.1 7 L3-11 3.5 1 L2-96 13.1 7 L3-36 3.6 1 Centennial-5 13.9 4 Whitestar 3.7 L8-67 14.0 7 L3-44 4.0 1 L3-136 14.6 1 Heartogold 4.3 1 L2-192 14.8 2 L3-15 4.4 1 L3-37 15.4 1 L3-64 4.5 10 L2-167 15.8 3 L3-130 4.7 1 LO-189 16.8 11 L3-151 4.7 1 Pelican Processor 17.2 3 L3-221 4.8 1 L2-116 17.3 3 L3-217 5.3 1 Goldrush 18.8 4 L3-152 5.4 1 Ll-193 19.2 7 L3-65 5.6 1 Centennial 19,3 12 Ll-128 5.8 Unit I Porto Rico 19.5 5 Coastal Sweet 6.2 1 Julian 20.6 11 L3-143 6.2 1 L2-74 21.8 2 L9-89 6.3 7 Centennial-1 22.4 2 L3-233 6.5 1 Centennial-2 22.3 8 L3-197 6.8 1 L9-66 25.3 2 LO-241 7.2 NC-210 28.8 1 L3-225 7.4 1 L2-66 32.6 1 L2-185 7.9 Rose Goldrush 35.7 2 L2-175 8.1 B-7078 41.6 1 L3-252 8.2 1 NC-215 45,6 1 L3-114 9.1 1 L9-143 56.8 1 Centennial T 9.4 1
*Mean severity indices for number of tests indicated. 59
Table 18. Percent and mean percentages of roots with injury caused by banded cucumber beetle larvae in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966.
Locations St. Ville Mean Cultivar Gabriel Hessmer Platte Scott Clinton Percentage
L3-64 1.9 10.7 0.0 19.4 5.0 7.4 Centennial-2 - -- - 7.8 7.8 L2-116 8.9 - 2.1 13.0 13.7 9.4 Rose Centennial 22.3 - 1.1 15.7 - 13.0 L3-66 6.9 25.4 0.0 20.2 - 13.1 L3-221 4.6 34.0 2.3 14.3 - 13.8 L3-5 •M - 0.0 29.0 - 14.5 L9-39 - --- 17.1 17.1 L3-39 16.1 31.6 2.2 24.7 11.2 17.2 Ll-193 21.1 37.6 0.0 24.2 15.9 19.8 Centennial-1 - - - - 20.4 ' 20.4 Julian 29.1 40.2 1.0 - 13.6 21.0 1,3-217 10.0 34.9 0.0 40.8 22.9 21.7 Centennial 34.8 25.9 0.0 28.0 22.9 22.3 Ll-35 41.7 29.0 4.1 21.1 - 24.0 LO-132 34.2 41.7 1.1 38.1 6.0 24.2 L2-61 25.8 36.7 4.1 33.8 24.0 24.9 Centennial-4 38.2 -- , -- 38.2. Centennial-8 38.5 - --- 38.5 LO-246 76.0 -- 48.9 12.5 45.8 • L3-179 - 54.5 - -- 54.5
LSD @ .05 22.50 20.58 NS 14.71 12.29 @ .01 30.05 NS NS 19.70 NS 60
Table 19. Severity and mean severity indices of roots with injury caused by banded cucumber beetle larvae in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966.
Locations St. Vi'lle Severity Cultivar Gabriel Hessmer Platte Scott Clinton Index
L3-64 0.7 4.5 0.0 7.4 1.8 2.9 Centennial-2 - - -- 2.9 2.9 L2-116 4.1 - 0.8 5.2 4.2 3.6 Rose Centennial 6.7 - 0.3 6.8 - 4.6 L3-66 2.6 9.8 0.0 7.5 - 5.0 L3-5 - - 0.0 10.9 - 5.5 L9-39 - --- 6.1 6.1 L3-221 1.5 18.1 1.5 5.9 - 6.8 Centennial-1 _ -- - 6.8 6.8 L3-39 7.5 14.6 1.1 8.1 3.6 • 7.0 Ll-193 9.4 18.9 0.0 10.3 5.5 8.8 Julian 12.6 17.8 0.5 - 4.9 9.0 Centennial 16.3 10.8 0.0 11.4 9.1 9.5 LO-132 14.4 19.8 0.3 16.4 2.0 10.6 L2-61 12.1 17.6 1.5 14.7 8.5 10.9 L3-217 5.0 25.7 0.0 18.0 8.2 11.4 Ll-35 24.9 11.8 1.8 9.6 - 12.0 Centennial-4 14.2 ---- 14.2 Centennial--8 16.1 -- - - 16.1 LO-246 48.0 - - 22.6 4.4 25.0 L3-179 32.7 32.7
LSD @ .05 14.69 11.17 NS 6.82 4.63 @ .01 19.62 14.98 NS 9.13 NS 61
Table 20. Severity and mean severity indices of roots with injury caused by pale-striped flea beetle larvae in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966.
Locations St. Ville Severity Cultivar Gabriel Hessmer Platte Scott Clinton Index
Centennial-8 5.9 5.9 L9-39 ---- 7.0 7.0 Centennial-4 7.0 --- - 7.0 L3-64 0.0 2.8 0.0 24.8 8.6 7.2 L3-39 3.9 9.1 0.0 30.3 12.5 11.2 L3-221 3.1 12.1 0.0 32.2 - 11.8 L3-5 - - 0.3 24.2 - 12.3 Centennial 5.4 6.6 1.3 33.7 17.7 12.9 L2-116 2.6 - 1.3 42.7 10.0 14.2 L3-66 1.1 5.6 0.0 52.1 - 14.7 L3-217 0.0 8.1 0.0 45.9 20.4 14.9 L3-179 - 15.2 - -- 15.2 Julian 12.1 13.1 0.5 - 35.1 15.2 Rose Centennial 2.2 - 0.5 46.2 - 16.3 Ll-193 4.9 19.1 0.0 39.0 22.5 17.1 L2-61 3.4 10.3 0.0 43.8 31.3 17.8 Ll-35 12.6 14.3 0.5 44.9 - 18.1 LO-132 8.1 18.5 0.0 37.9 42.2 21.4 Centennial-2 -- -- 24.8 24.8 Centennial-1 - --- 31.3 31.3 LO-246 33.3 -- 49.1 13.7 32.0
LSD @ .05 10.63 NS NS NS 10.79 @ .01 14.20 NS NS NS 14.47 62
Table 21. Percent and mean percentages of roots with injury caused by wireworms in field-grown sweet potato cultivars at 5 loca tions in Louisiana, 1966.
Locations St. Ville Mean Cultivar Gabriel Hessmer Platte Scott Clinton Percentage
L3-64 0.0 5.8 0.0 10.6 2.1 3.7 L2-61 9.6 11.2 0.0 10.6 15.0 9.3 L2-116 5.3 - 1.0 9.2 24.4 10.0 L3-66 6.9 30.8 0.0 4.1 - 10.5 L3-5 - - 1.3 23.6 - 12.5 L9-39 ---- 12.9 12.9 Rose Centennial 31.6 - 0.0 9.3 - 13.6 L3-39 20.6 27.0 0.0 9.1 12.1 13.8 L3-217 4.0 16.7 0.0 29.2 29.5 ■ 15.9 L3-221 4.2 34.9 1.3 23.4 - 16.0 LO-132 22.6 44.2 0.0 12.3 5,0 16.8 Centennial-2 - - -- 18.3 18.3 Centennial-1 ---- 19.2 19.2 Centennial 38.3 25.6 4.9 21.8 14.0 20.9 Ll-35 36.6 39.1 4.3 37.7 - 29.4 Centennial-8 32.9 - - -- 32.9 Ll-193 50.6 48.6 4.2 34.4 33.4 34.2 Julian 55.0 52.8 2.1 - 38.5 37.1 LO-246 59.5 . -- 43.9 15.3 39.6 Centennial-4 41.8 - --- 41.8 L3-179 — 56.5 —— 56.5
LSD @ .05 21.74 23.17 NS 17.21 13.21 @ .01 29.04 31.08 NS 23.04 17.72 63
Table 22. Percent and mean percentages of roots with surface mining in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966.
Location St. Ville Mean Cultivar Gabriel Hessmer Platte Scott Clinton Percentage
Centennial-8 0.0 . _ 0.0 Centennial-4 0.0 - -- - 0.0 L3-179 - 0.0 - -- 0.0 L3-64 0.0 0.0 0.0 0.0 1.0 0.2 L3-66 0.0 0.0 0.9 1.3 - 0.5 L2-61 0.0 0.0 0.0 4.1 1.0 1.0 LO-132 0.0 0.0 0.0 0.0 6.0 1.2 Rose Centennial 0.0 - 0.0 4.0 - 1.3 Centennial 0.0 0.0 0.0 5.3 1.9 1.4 Centennial-2 --- - 1.9 1.9 L3-217 0.0 0.0 1.0 4.0 5.0 2.0 Centennial-1 ---- 2.0 2.0 L3-39 0.0 2.4 1.1 1.3 6.1 2.2 L3-221 0.0 1.0 1.0 9.0 - 2.8 L2-116 0.0 - 2.0 4.0 4.0 2.5 Ll-193 0.0 1.0 0.0 1.5 14.7 3.4 Ll-35 0.0 1.0 5.4 11.5 - 4.5 Julian 0.0 3.1 2.1 - 13.3 4.6 L3-5 - - 2.4 10.6 - 6.5 L9-39 . ---- 8.9 8.9 LO-246 0.0 -- 14.6 18.6 11.1.
LSD @ .05 NS NS 2.40 NS 4.97 @ .01 NS NS 3.21 NS 6.67 64
Table 23. Wirewomi and raining injury on roots of sweet potato cultivars at Lawtell, Louisiana, 1965.
Percent root injury Cultivar Wireworm Mining
L2-185 8.0 6.0 L3-64 8.1 0.0 White Star 13.0 15.0 Pelican Processor 19.0 3.0 Centennial 30.0 0.0 Julian 32.4 5.0 LO-132 33.8 2.0 L4-89 35.0 0.0 Centennial-4 37.0 0.0 LS-67 39.7 0.0 L2-196 40.0 0.0 LO-241 40.6 2.0 Centennial-8 46.7 0.0 Unit I Porto Rico 48.0 3.0 L9-89 50.0 2.0 LO-246 51.0 5.0 LI-93 57.4 0.0 LO-189 75.0 2.0 Goldx-ush 75.0 9.0 65
Table 24. Percent and mean percentages of roots with injury caused by sweet potato flea beetle larvae in sweet potato cultivars at 5 locations in Louisiana, 1966.
St. Ville Mean Cultivar Gabriel Hessmer Platte Scott Clinton Percentage
L3-64 0.0 0.0 0.0 6.3 0.0 1.3 Rose Centennial 2.1 - 0.0 6.6 - 2.9 L3-66 4.8 4.6 0.0 2.7 - 3.0
Centennial-8 3.3 - - ■ - - 3.3 L3-5 - - 0.0 9.1 - 4.6 L2-116 0.0 - 0.0 13.0 7.9 5.2 L3-221 4.6 11.1 0.0 6.5 - 5.6 LO-132 7.8 6.4 0.0 7.9 10.0 6.4 L3-179 - 6.7 -- - 6.7 Centennial-4 7.0 - - -- 7.0 L3-39 7.1 9.8 2.2 9.0 9.1 7.4 Centennial 12.9 1.7 1.0 13.0 9.2 7.6 Centennial-2 -- - - 7.8 7.8 L2-61 4.1 5.4 0.0 20.9 10.0 8.1 Ll-193 12.0 2.8 0.0 7.0 25.7 9.5 L3-217 10.0 2.3 0.0 8.2 29.5 10.0 Ll-35 17.7 5.7 1.0 16.2 - 10.2 Julian 14.5 2.2 1.1 - 28.5 11.6 L9-39 ---- 13.9 13.9 LO-246 29.0 -- 8.3 10.3 15.9 Centennial-1 — —— — 19.2 19.2
LSD @ .05 9.46 NS NS NS 14.39 @ .01 12.63 NS NS NS 19.30 66
Table 25. Percent and mean percentages of roots with injury caused by grubs in field-grown sweet potato cultivars at 5 locations in Louisiana, 1966.
Location St. Ville Mean Cultivar Gabriel Hessmer Platte Scott Clinton Percentage
L3-139 0.0 —, 0.0 L3-64 0.0 0.0 2.2 0.0 2.8 1.0 L3-217 0.0 0.0 0.0 0.0 5.8 1.2 L3-5 - - 0.0 2.6 - 1.3 Rose Centennial 4.2 - 1.0 0.0 - 1.7 L3-39 9.8 0.0 1.1 1.3 0.0 2.4 Ll-193 1.6 3.9 0.0 0.0 7.2 2.5 L2-116 2.2 - 1.0 0.0 6.9 2.5 L3-66 9.3 0.0 1.0 0.0 - 2.6 Ll-35 11.5 0.0 0.0 0.0 - 2.9 Centennial-2 -- -- 3.0 3.0 Julian 7.1 0.0 2.0 - 3.2 3.1 7,9-39 -- - - 3.1 3.1 Centennial 10.7 0.0 5.0 0.0 1.0 3.3 L2-61 14.7 0.0 0.0 0.0 2.0 3.3 L0-132 15.3 1.1 2.1 0.0 1.0 3.9 Centennial-1 - -- - 5.8 5.8 Centennial-8 9.0 - --- 9.0 Centennial-4 10.4 - - -- 10.4 L3-221 39.1 1.1 1.3 6.5 - 12.0 LO-246 41.5 “ 4.2 5.2 17.0
LSD @ .05 23.09 NS NS NS NS 67
Table 26. Percent of roots with injury caused by sweet potato weevils in field-grown sweet potato cultivars at Scott, Louisiana, 1966.
Mean Percent Cultivar Root Damage
L2-61 0.0 L3-39 0.0 L3-66 0.0 L3-217 0.0 Ll-193 0.0 LO-132 1.2 L3-64 1.3 L3-5 1.3 L2--217 1.3 L3-221 2.6 LO-246 2.9 Rose Centennial 4.0 Centennial 4.8 Ll-35 6.7
NS 68
Table 27. Effect of black plastic mulch and cultivars on the severity of sweet potato root injury by Diabrotica balteata, Scott, Louisiana.
Treatment______Severity Index
Unit I Porto Rico without Plastic 8.2 Unit I Porto Rico with Black Plastic 12.7 L4-89 without Plastic 12.2 L4-89 with Black Plastic 8.6
NS
Planted May 20, 1964; harvested Sept. 22, 1964.
Table 28. Effect of black plastic mulch and cultivars on the severity of sweet potato root injury by Diabrotica balteata, Church Point, Louisiana.
Treatment Severity Index
Goldrush without Plastic 33.06 Goldrush with Black Plastic 34.57 L4-89 without Plastic 12.70 L4-89 with Black Plastic 18.07
NS
Planted May 21, 1964; harvested Sept. 24, 1964. 69
Table 29. Effect of black plastic mulch and cultivars on the severity of sweet potato root injury by Diabrotica balteata, Lewisburg, Louisiana.
Treatment Severity Index
Centennial without Plastic 8.8 Centennial with Black Plastic 7.2 L4-89 without Plastic 1.1 L4-89 with Black Plastic 1.6
LSD @ .05 3.82 @ .01 5.21
Planted June 9, 1964; harvested Oct. 22, 1964.
Table 30. Effect of mulches on the severity of Centennial sweet potato’ root iniury by Diabrotica balteata, Essen Lane Farm, Baton Rouge, Louisiana.
Treatment Severity Index
Check 1.17 Clear Plastic 1.57 White Plastic 2.10 Spray Asphalt 3.00 Black Plastic 5.43
NS
Planted May 27, 1964; harvested Oct. 25, 1964. 70
Table 31. Effect of cultivars on the mean injury of sweet potato roots by larvae of Diabrotica balteata in controlled environment, Louisiana State University, Baton Rouge, Louisiana, 1964.
Cultivar Small Holes Medium Holes Large Holes Total Holes
L4-89 6.3 1.3 0.0 7.6 L9-125 3.5 1.8 4.0 9.3 L3-64 7.5 1.8 0.8 10.1 L9-39 10.0 1.8 0.0 11.8 L8-3 9.3 3.0 0.3 12.6 L9-143 10.3 1.8 1.0 13.1 L8-67 11.0 5.6 1.3 17.9 L9-23 10.0 6.8 2.5 19.3 Goldrush 15.0 4.8 0.5 20.3 L9-56 12.8 4.8 2.8 20.4 Centennial 18.0 4.8 1.3 24.1 L9-89 16.8 6.6 0.8 24.2 L4-50 20.3 6.8 0.8 27.9 L9-66 26.3 9.6 2.0 37.9
LSD @ .05 9.9 NS NS 14.4 @ .01 13.3 NS NS 19.3 71
Table 32. Severity indices of sweet potato root injury by larvae of Diabrotica balteata on greenhouse-grown cultivars at L.S.U., Baton Rouge, Louisiana.
Cultivar Severity Index Cultivar Severity Index
Jersey Orange 3.33 L0-189 14.19 Julian 4.58 L3-93 14.45 L3-64 P 4.95 L8-67 14.83 L3-64 P 5.80 L-240 15.00 L0-135 7.30 L0-193 15.73 Centennial-T 7.50 Oklahoma 51 19.58 LO-241 8.35 L3-64 x L3-80 20.40 LO-138 8.45 L0-132 20.80 L3-64 P 8.55 L0-183 21.78 L3-64 9.00 L3-64 x L3-80 22.48 L3-64 P 10.18 NC-188 23.55 L2-196 10.66 Georgia Red 24.38 L3-64 x L3-80 10.70 L3-64 P 25.15 L3-64 x L3-80 10.80 L0-93 25.38 L9-125 11.70 L9-66 25.53 L9-89 11.83 L3-64 P 27.08 L0-240 12.48 L4-89 27.50 L3-64 P 12.98 L3-64 P 30.00 LO-129 13.53 L2-167 35.00 L3-64 P 14.10 Centennial 36.30 L3-64 P 14.15
NS NS
Planted Nov. 24, 1964; harvested July 20, 1965. 72
Table 33. Study of resistance of seedlings from a cross of L3-64 x Nemagold and other cultivars to banded cucumber beetle injury.
______L3-64 x Nemagold______L3-64 x Nemagold______Seedling Severity No. Roots Seedling Severity No. Roots No. Index Indexed No. Index Indexed
1 0.0 30 43 2.2 22 2 0.0 7 44 2.3 12 3 0.0 19 45 2.3 53 4 0.0 12 46 2.3 42 5 0.0 21 47 2.6 47 6 0.0 6 48 2.7 27 7 0.0 45 49 2.8 62 8 0.0 10 50 2.8 35 9 0.0 9 51 2.8 44 10 0.0 7 52 3.0 48 11 0.0 25 53 3.0 25 12 0.0 17 54 3.2 23 13 0.0 35 55 3.3 37 14 0.0 9 56 3.3 36 15 0.0 11 57 3.5 35 16 0.0 9 58 3.5 7 17 0.0 32 59 3.5 50 18 0.0 33 60 3.6 55 19 0.0 8 61 3.7 40 20 0.0 45 62 3.7 38 21 0.0 15 63 3.8 46 22 0.5 43 64 3.8 26 23 0.6 40 65 3.9 44 24 0.7 35 66 3.9 32 25 0.8 31 67 4.0 74 26 0.8 30 68 4.0 37 27 0.9 27 69 4.0 50 28 1.1 22 70 4.0 55 29 1.1 63 71 4.1 6 30 1.1 63 72 4.1 30 31 1.4 68 73 4.1 6 32 1.6 30 74 4.5 22 33 1.6 60 75 4.5 25 34 1.7 18 76 4.6 65 35 1.7 18 77 4.7 47 36 1.8 5 3 78 4.7 21 37 1.8 16 79 4.8 57 38 1.9 13 80 5.0 35 39 1.9 26 81 5.2 18 40 1.9 13 82 5.2 24 41 2.0 25 83 5.2 48 42 2.0 12 84 5.3 19
(Continued) 73
Table 33. Continued
______L3-64 x Nemagold______L3-64 x Nemagold______Seedling Severity No. Roots Seedling Severity No. Roots No. Index Indexed No. Index Indexed
85 5.4 55 129 11.2 51 86 5.5 9 130 11.2 40 87 5.5 54 131 11.4 24 88 5.7 30 132 11.5 41 89 5.7 69 133 11.6 30 90 5.8 30 134 11.7 34 91 6.0 29 135 11.8 40 92 6.2 28 136 12.1 39 93 6.2 16 137 12.2 43 94 6.2 28 138 12.5 12 95 6.4 35 139 12.5 4 96 6.4 81 140 12.5 56 97 6.5 18 141 12.7 51 98 6.6 15 142 12.9 61 99 7.2 24 143 13.0 46 100 7.2 76 144 13.0 42 101 7.3 78 145 13.2 70 102 7.3 17 146 13.7 20 103 7.4 52 147 13.7 34 104 7.5 10 148 13.8 18 105 7.6 36 149 14.0 25 106 7.7 55 150 14.0 48 107 7.8 38 151 14.5 50 108 8.3 24 152 15.1 216 109 8.3 45 153 15.6 51 110 8.3 15 154 16.3 61 111 8.3 42 155 16.3 48 112 8.4 80 156 16.6 30 113 9.0 21 157 17.5 30 114 9.3 16 158 17.9 32 115 9.5 34 159 18.7 40 116 9.6 57 160 18.9 29 117 9.7 48 161 18.9 37 118 9.7 72 162 19.0 38 119 9.8 43 163 19.3 49 120 9.8 48 164 19.4 63 121 10.0 30 165 19.6 42 122 10.1 59 166 19.8 38 123 10.2 51 167 20.0 40 124 10.3 29 168 20.1 46 125 10.7 65 169 20.4 11 126 11.0 43 170 20.8 12 127 11.1 9 171 20.9 37 128 11.1 18 172 23.6 18
(Continued) 74
Table 33. Continued
______L3-64 x Nemagold______Seedling Severity No. Roots No. Index Indexed
173 24.3 41 174 30.8 74 175 32.3 ' 51 176 32.3 41 177 38.3 15
L3-64 6.8 55 Nemagold 9.0 55 Centennial 37.5 36 75
o m
o 17.5% T3 O m 0.0 1.0-5.0 20.1-38.3 Severity Index Very Mod. Mod. Very Res. Res. Res. Sus. Sus. Sus. Figure 1. Frequency distribution of sweet potato seedlings into classes as to resistance to banded cucumber beetle larvae in a cross of L3-64 x Nemagold. DISCUSSION OF RESULTS There is a growing need for breeding sweet potatoes and other crops for resistance to insects, especially since the Food and Drug Administration is applying more stringent regulations governing the use of pesticides. A limited amount of research relative to breeding for resistance to insects has been done in previous years. This was partly due to the availability of effective, and economical insecticides .to control most sweet potato insects. In this study, a concerted effort was made to screen and find sweet potato germplasm with resist ance to the banded cucumber beetle. Painter (63) divided the phenomenon of insect resistance in plants into three mechanisms as follows: (1) Preference or Non- Preference, (2) Antibiosis and (3) Tolerance. Kantack (44, 45) found in 1960 that most of the injury on sweet potato roots in Louisiana resulted from the larvae of the banded cucumber beetle. Also, Pitre and Kantack (65) reported that the banded cucumber beetle had become an increasingly serious pest since 1958. They reported that six or seven generations were produced each year and the larvae of this insect was present in the soil every month of the year. In preliminary studies, Kantack (47) found that L3-64 showed very little insect injury as compared to Centennial and other cultivars. In this study, L3-64 was found to have a considerable amount of resistance to the banded cucumber beetle larvae and other insects. Also, other cultivars such as L4-89, Ll-111, Ll-128, LO-241 and others 76 77 were found to have considerable resistance to this insect. Cultivars showing resistance to larvae of the banded cucumber beetle in general, do not exhibit this same degree of resistance to larvae of the pale- striped flea beetle. Centennial consistently showed a high degree of susceptibility to injury by larvae of the banded cucumber beetle in this study. Cuthbert (15) tested and evaluated a large number of cultivars for resistance to soil insects and found L3-64 and others possessed a high degree of resistance. In this study, a population of 177 seed lings were grown from a cross of L3-64 x Nemagold. A large number of seedlings segregated for resistance to the banded cucumber beetle. This resistance is a quantitative character and through quantitative breeding recombinations having good horticultural characters and resistance to soil insects should not be too difficult to obtain through a breeding program. In this study, subjective measurements were used to measure root injury. Severity indices of fleshy roots of cultivars showed great differences among cultivars. The author feels that field evaluation of cultivars is a valid approach in measuring the degree of resistance of sweet potato cultivars to injury by soil insects.if the soil is infested with a high population of these insects. Significant positive correlation coefficients between high severity indices and large larval populations in the soil at some locations where these tests vrere coxi- ducted indicated that these data are highly accurate in determining the amount and type of soil insect injury to fleshy sweet potato roots (74, 75). Populations of insect species differed among locations and 78 this probably accounts for variability and low injury reading on the same severity of root injury shown in cultivars at certain locations. Also, large differences among replications resulted in too large an error to measure significant differences in some tests. The severity index reported in the results of this study is a measurement of the severity of injury sustained by a particular cul tivar at any location. The severity index differs from the percent of roots injured since it does show how severe the injury is rather than the percent of fleshy roots that were damaged. The severity index is more meaningful in determining resistance of cultivars to soil insects than just measuring the percent of roots injured and is useful to the researcher for measuring differences in resistance among cultivars at one location. There were a total of 22 field experiments conducted in 1964 through 1966 to evaluate a large number of cultivars as to resistance to soil insects, especially banded cucumber beetle larvae. During that period of time the growers in Louisiana were incurring large losses from injury to the sweet potato fleshy roots. The major varie ties grown in these areas of production were Centennial, Goldrush, Unit I Porto Rico and some Julian. Since most of the acreage was in Centennial the greatest losses resulted from root damage to this variety. The exact reasons as to why serious losses were occurring at that time from soil insects was not known, but, it was generally believed that it was due to a large soybean acreage which provided a good habitat for the insects and possibly the killing of predators of the insect larvae. 79 In most cases the locations for field tests were areas that were previously reported to have had sweet potato root injury from soil insects. In 1964 injury to sweet potato roots were generally severe at each of four locations. For example, in. a test at Baton Rouge, La. L3-64 had a severity index of 5.8 compared to 49.95 for E-1097-57 and Centennial had an index reading of 29.98. This indicated that the population of banded cucumber beetle larvae was adequate to provide a suitable infestation. As previously indicated workers (74, 75) reported an association of high insect injury to sweet potato fleshy roots with large populations of larvae of the banded cucumber beetle. In 1965 there were 12 field tests conducted in different areas of South Louisiana. In seven of these locations the roots of most of the cultivars were severely injured by larvae of the banded cucumber beetle. There were great differences among cultivars at these loca tions. In each location where L3-64 was grown a low severity index was recorded. In contrast, a high severity index was generally recorded for Centennial. Large differences were recorded among culti vars at some locations, however, the differences among cultivars were not significant and this is probably due to uneven distribution of insects within any one test area. In 1966 there were five field experiments conducted in South Louisiana. Good banded cucumber beetle larvae infestation occurred in all but one location. Significant differences among cultivars were also fouud to occur in all but one location. In general fleshy roots of 80 L3-64 had low severity indices and roots of Centennial continued to be severely injured by banded cucumber beetle larvae. In this study an effort was made to find a suitable technique for screening sweet potato cultivars for resistance to damage of the banded cucumber beetle. Two experiments were conducted, the first consisting of 14 of the more promising cultivars including Centennial and L3-64 as the susceptible and resistant standards of comparison, respectively, and the second consisted of a total of 117 cultivars. The procedure of these experiments are described in the materials and methods. After the first test, it appeared that this method of screen ing sweet potato cultivars for resistance to larvae of the banded cucumber beetle might be of value. Results are presented in Table 31 and it is interesting to note that many of the same cultivars showing resistance to the banded cucumber beetle in this controlled study also showed resistance when evaluated under field conditions. Unfortunately, the second feeding study was unsuccessful in that the larvae died before fleshy root injury was obtained. This might possibly be due to the fact that corn roots were not available for larvae to feed on until they were in the proper instar for feeding on fleshy sweet potato roots. It was felt that possibly a severity index of practical value could be obtained in controlled greenhouse feeding studies by testing attached growing fleshy sweet potato roots. As shewn in Table 32, several first year cultivars of a L3-64 polycross progeny exhibited a high degree of resistance to the banded cucumber beetle larvae. Although four repli cations were used in this study, space available allowed only one plant per replication and significant differences among cultivars could not 81 be measured. A limited number of cultivars could be effectively tested by this technique at a time of the year when other methods would not be practical. Mulching studies were conducted to determine if soil coverings could effectively prevent oviposition by the banded cucumber beetle, thus reducing the larval infestation. It was further felt that if this could be accomplished that mulches might possibly be of benefit in other ways. No significant differences in fleshy root injury could be measured between mulched and non-mulched treatments, the only dif ferences in the tests were due to cultivars. The black polyethylene mulch treatments located in areas of high rainfall caused an exces sive amount of fleshy sweet potato roots to rot. The rotted sweet potato roots were possibly the result of lack of oxygen following excessive rains. Slight differences were observed among the different colored plastics, but these differences were not significant. The asphalt emulsion spray was of no more benefit than plastics and within a few weeks of application, cracking occurred and weeds became a severe problem. SUMMARY AND CONCLUSIONS Studies were conducted from 1964 through 1966 to study the resistance of fleshy roots of sweet potato cultivar to injury by larvae of the banded cucumber beetle and certain other insects under field conditions. In 1964 the effect of mulches as a means of reducing injury to sweet potato storage roots by certain soil insects was inves tigated. Also, in 1964 an attempt was made to develop a suitable laboratory technique for screening sweet potato cultivars for resist ance to larvae of the banded cucumber beetle. A controlled greenhouse feeding study to screen sweet potato breeding material for resistance was initiated in 1964 and completed in 1965. A genetic study of resistance of seedlings from a control cross was also conducted in 1965. In 1964 a large number of cultivars were planted at Lewisburg, Baton Rouge, Scott and Arnaudville, La. in order to determine their differences in injury by banded cucumber beetle larvae. No statistical differences among cultivars could be measured at Lewisburg and Scott, La. Highly significant differences among cultivars were found at Baton Rouge, La. and the six least injured cultivars in this test were Louisiana seedlings. L8-67 and L3-64 had the least fleshy root injury. Highly significant differences among cultivars were also shown in the Arnaudville study. The least injury was found on roots of NC-210 and L3-64. Severity indices of sweet potato root injury by larvae of the banded cucumber beetle on cultivars from several locations in 1965 82 83 ranged from 0.4 to 56.8. The mean severity index of L3-64 as an average of 10 tests was 4.5 as compared to 19.3 for Centennial roots as an average of 12 tests. L3-64 was found to be highly resistant to banded cucumber beetle larvae injury. As an average of five locations in 1966 L3-64 had the least root injury by banded cucumber beetle larvae. Of 21 entries evaluated Centennial ranked thirteenth in severity of root injury. Significant differences among cultivars were tabulated at four of the five locations. The results obtained from studies in 1966 showed that in general, L3-64 consistently suffered relatively little fleshy root injury from larvae of pale-striped flea beetle, wireworm, surface mining, larvae of the sweet potato flea beetle, grubs, and sweet potato weevil. Investigations were conducted in 1964 using synthetic mulches in an effort to prevent oviposition into the soil by the banded cucumber beetle. The differences betx^een mulched and non-mulched treatments were small and not significant. Cultivars xjere responsible for dif-. ferences that could be measured rather than mulches. L4-89 roots shoxred more resistance to the banded cucumber beetle larvae than roots of Centennial, Goldrush, and Unit I Porto Rico under those experimental conditions. The injury to detached sweet potato roots by larvae of the banded cucumber beetle was measured on 14 cultivars in a controlled environment. Cultivars L4-89 and L9-125 were the only two that had significantly fe\7er total feeding holes per root than Centennial which had an average of 24,1. The root injury of L3-64 was less than Centennial and approached significance. Forty-one cultivars were evaluated for resistance to banded cucumber beetle larvae in a greenhouse experiment in 1964 and 1965. Although no statistical differences could be measured among cultivars L3-64 ranked tenth as to severity of root injury and in general those cultivars with L3-64 as a parent had relatively low severity indices. In 1965 a genetic study was conducted using 177 seedlings from a controlled cross of L3-64 x Nemagold, both moderately resistant parents. The frequency distribution of this seedling population rela tive to the degree of injury by banded cucumber beetle larvae showed a discontinuous variation. There were 15.3 percent of the seedlings rated as very resistant, 29.9 percent resistant, 22.6 moderately resistant, 17.5 percent moderately susceptible, 9.0 percent susceptible and 5.7 percent very susceptible. Resistance of sweet potato seedlings to banded cucumber beetle larvae appears to be a quantitative character and a large number of seedlings segregated for resistance in the cross L3-64 x Nemagold. BIBLIOGRAPHY 1. Allen, T. C. 1947. 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A history of applied entomology. Smithsn. Misc. Collect. 34. 564 p. 34. Hughes, M. B. 1947. Canteloupe breeding. S. Car. Expt. Sta. of Clemson Agr. Col. Ann. Rpt. 59:155-157. 35. Isely, D. 1928. Relation of leaf color and leaf size to boll weevil infestation. Jour. Econ. Ent. 21:553-559. 36. Isely, D. 1935. Relation of hosts to abundance of cotton boll- worm. Ark. Agr. Expt. Sta. Bui. 320. 37. Ivanoff, S. S. 1945. A seedling method for testing aphid resistance and its application to breeding and inheritance studies in cucurbits and other plants. Jour. Hered. 36:357-361. 38. Jones, H. A., S. F. Bailey, and S. L. Emsweller. 1934. Thrip resistance in the onion. Hilgardia 8:215-232. 39. Kantack, E. J. and E. H. Floyd. 1956. Control of some insects which damage the roots of sweet potatoes in the field. Jour. Econ. Ent. 49(6):766-768. 40. Kantack, E. J. 1957. Insect studies. Ann. Prog. Rpt. La. State Univ. Hort. Res. Cir. No. 39:10, 35. 41. Kantack, E. J. 1958. Insect studies. Ann. Prog. Rpt. La. State Univ. Hort. Res. Cir. No. 41:13, 49. 88 42. Kantack, E. J. 1959. Insect Studies. Ann. Prog. Rpt. La. State Univ. Hort. Res. Cir. No. 44:7-8. 43. Kantack, E. J. 1959. Insects and sweet potatoes. Insect condi tions in La. La. State Univ. Ext. Res. Dept. Pub. 2:25-26. 44. Kantack, E. J. 1960. Insect studies. Ann. Prog. Rpt. La. State Univ. Hort. Res. Cir. No. 46:7. 45. Kantack, E. J. 1960. Status of banded cucumber beetle on sweet potato. La. State Univ. Ent. Res. Dept. Pub. 3:25. 46. Kantack, E. J. 1961. Twenty years of cooperative sweet potato research, 1939-1959. National Sweet Potato Collaborators, pp. 55-64. 47. Kantack, E. J. 1962. Insect studies. Ann. Prog. Rpt. La. State Univ. Hort. Res. Cir. No. 50:8. 48. Kennedy, C. II. 1927. Some non-nervous factors that condition the sensitivity of insects to moisture, temperature, light, and odors. Ent. Soc. Amer. Ann. 20:87-106. 49. Langford, G. S., M. H. Muma, and E. N. Cory. 1943. Attractiveness of certain plant constituents to the Japanese beetle. Jour. Econ. Ent. 36:248-252. 50. Mclndoo, N. E. 1935. The relative attractiveness of certain solanaceous plants to the Colorado potato beetle. Proc. Ent. Soc. Wash. 37:36-42. 51. MacLeod, G. F. 1933. Some examples of varietal resistance of plants to insect attack. Jour. Econ. Ent. 26:62-66. 52. McColloch, J. W. 1920. A study of the oviposition of the corn earworm with relation to certain phases of life economy.and measures of control. Jour. Econ. Ent. 13:242-255. 53. Macrovitch, S. 1946. Insects injurious to sweet potato tubers in Tennessee. Univ. Tenn. Agr. Expt. Sta. Bui. 202, 11 p. 54. Metzger, F. W. and D. H. Grant. 1932. Rapellency to the Japanese beetle o>;f extracts made from plants immune to attack. U. S.. Dept. Agr. Tech. Bui. 299. 55. Metzger, P. A., P. A. van der Meulen, and C. W. Mell. 1934. The relation of the sugar content and odor of clarified extracts of plants to their susceptibility to attack by the Japanese beetle. Jour. Agr. Res. 49:1001-1008. 56. Moore, J. B. 1937. Reactions of aphids to colored insecticides. Jour. Econ. Ent. 30:305-309. 89 57. Montelaro, Joseph, Weston J. Martin, and Edmon J. Kantack. 1961. Louisiana sweet potatoes. Agr. Ext. Pub. 1121. 58. Montelaro, Joseph, Weston J. Martin, and Edmon J. Kantack. 1967. Sweet potatoes in Louisiana. Coop. Ext. Pub. 1450. 59. Mungomery, R. W. and J. H. Buzacott. 1940. Varietal resistance to cane grubs. Cane Gr. Quar. Bui. 8:45-47. 60. Painter, R. H., R. 0. Snelling, and A. M. Brunson. 1935. Hybrid vigor and other factors in relation to chinch bug resistance in corn. Jour. Econ. Ent. 28:1025-1030. 61. Painter, R. H. 1936. The food of insects and its relation to resistance of plants to insect attack. Amer. Nat. 70:547-566. 62. Painter, R. H. 1941. The economic value and biologic signifi cance of plant resistance to insect attack. Jour. Econ. Ent. 34:358-367. 63. Painter, R. H. 1968. Insect Resistance on Crop Plants. The University Press of Kansas, Lawrence and London. 64. Pepper, J. H. and E. Hastings. 1943. Biochemical studies of the sugar beet webworm, Loxostege sticticalis L. with special reference to fatty acids and their relation to diapause and sterility. Mont. Agr. Expt. Sta. Tech. Bui. 413. 65. Pitre, Henry N., Jr. and Edmon J. Kantack. 1962. Biology of the banded cucumber beetle, Diabrotica balteata, in Louisiana. Jour. Econ. Ent. 55:904-906. 66. Richmond, E. A. 1937. The olfactory response of the Japanese beetle, Popillia japonica Newn. Ent. Soc. Wash. Proc. 29:36-44. 67. Shorey, H. II. and L. D. Anderson. 1963. Biology and control of the morning-glory Leaf miner, Bedellia somnulentella, on sweet potatoes. Jour. Econ. Ent. 53:1119-1122. 68. Sleesman, J. P. 1940. Resistance in wild potatoes to attaclc by the potato leaf hopper and the potato flea beetle. Amer. Pot. Jour. 17 :9-12. 69. Snelling, R. 0., R. II. Painter, J. II. Parker, and W. M. Osborn. 1937. Resistance of sorghums to the chinch bug. U. S. Dept. Agr. Tech. Bui. 585. 70. Snelling, R. 0. 1941. Resistance of plants to insect attack. Bot. Rev. 7:543-586. 71. Trager, W. 1947. Insect nutrition. Biol. Rev. 22:148-177. 90 72. Uvarov, B. P. 1933. Conditioned reflexes in insect behavior. Fifth Internatl. Cong. Ent. Proc. 353-360. 73. Walker, John R. 1966. Reproductive potential of the sweet potato weevil after exposure to ionizing radiations. Jour. Econ. Ent. 59:1206-1208. 74. Wascom, Bunnie W., Terae P. Hernandez, Julian C. Miller, Aithel McMahon, Raymond Schelliriger, L. D. Newsom, and E. J. Kantack. 1965. Evaluation of selected sweet potato varieties for resistance to the banded cucumber beetle. Fourth Biannual Rpt. to USDA, Contract No. 12-14-100-7709 (33). Jan. 1-June 30. 75. Wascora, Bunnie W., Teme P. Hernandez, Julian C. Miller, Donald W. Newsom, W. A. Young, Aithel McMahon, Raymond Sche'llingei, E. J. Kantack, and L. D. Newsom. 1965. Evaluation of selected sweet potato varieties for resistance to the banded cucumber beetle. Fifth Biannual Rpt. and Summary to USDA, Contract No. 12-14-100-7709 (33) July 1-Dec. 31. 76. Weiss, H. B., E. E. McCoy, Jr., and W. M. Boyd. 1944. Group motor responses of adult and larval forms of insects to differ ent wave lengths of light. N. Y. Ent. Soc. Jour. 52:27-43. 77. Went, F. W. 1940. Local and generalized defense reactions in plants and animals, local reactions in plants. Amer. Nat. 74:107-116. AUTOBIOGRAPHY Bunnie William Wascom was born in Tangipahoa Parish on July 5, 1933. He attended Hammond Grammar School and was graduated from Hammond High School in May, 1951. He worked with Baroid, a division of National Lead Company, from June, 1951 to May, 1953, at which time he was married to Mary Loretta Hughes and in the same month he was inducted into the United States Army. His military obligation was fulfilled in May, 1955, and he was honorably discharged. In 1955 he returned to his former job and worked until June, 1956 at which time he entered Southeastern Louisiana University at Hammond, Louisiana. He was graduated from Southeastern Louisiana University with a Bachelor of Science degree in Horticulture in May, 1959 and employed by the Louisiana State University Department of Horticulture at the Sweet Potato Research Center at Chase, Louisiana. He worked there as an Instructor in Horticulture until September, 1962, at which time he returned to the Baton Rouge Campus to pursue his graduate studies and served as an Instructor in Horticulture. He completed his Master of Science degree in Horticulture in January, 1964 and continued his studies toward a terminal degree. In January, 1967, he accepted a posi tion with the Louisiana Cooperative Extension Service where he is still employed as an Extension Horticulturist. He is now a candidate for the degree of Doctor of Philosophy. 91 EXAMINATION AND THESIS REPORT Candidate: Bunnie William Wascom Major Field: Horticulture Title of Thesis: Resistance of Sweet Potato Cultivars and the Effect of Cultural Methods on Control of Soil Insect Damage Approved: Major Professor and Chairman &X- Dean of the Graduate School EXAMINING COMMITTEE: ,9 f xyQ(cl^\ Date of Examination: December 18, 1970