Pest Of Peanuts Research Articles

Laboratory Bioassay Evaluating Peanut Seedlings for Resistance to the Southern Corn Rootworm, Diabrotica undecimpunctata howardi Barber (Coleoptera: Chrysomelidae)

Abstract The objective of this study was to develop a laboratory bioassay that consistently distinguishes peanut genotypes (Arachis hypogaea L.) based on their potential susceptibility or resistance to the southern corn root-worm (SCR), Diabrotica undecimpunctata howardi Barber, a major soil insect pest of peanut in North Carolina, Virginia, and other states. The susceptibility or resistance of a peanut genotype to the SCR was characterized by the survival, development, and mean weight of the pest after feeding for 14 d on seedlings of different peanut genotypes. An initial 14 d seedling bioassay demonstrated the ability of the technique to separate a susceptible cultivar (NC 7) from a resistant cultivar (NC 6) based on the percentage of SCR that survived after 14 d, the percentages and mean weight of surviving SCR in larvae, prepupae, and pupae. Subsequently, two 14 d seedling bioassays evaluated five additional peanut genotypes that were believed to have some resistance to the SCR (N97059N, N92069L, VA 861101, VT 9506114–1, NC-GP WS 9) along with the susceptible (NC 7) and resistant (NC 6) controls. The final two bioassays were modified to test the differences in the percentages of SCR adults that emerged and the time required for adult emergence after feeding as larvae on the susceptible (NC 7) and resistant (NC 6) peanut seedlings. The 14 d seedling bioassay represents an improvement over earlier seedling bioassays because of its consistent ability to distinguish susceptible and resistant peanut genotypes, and because of the diversity of parameters measured. It consistently separated the susceptible (NC 7) and resistant (NC 6) controls, with one or more of the parameters measured. The breeding line N92069L and the germplasm line NC-GP WS 9 were shown to result in significantly lower survival of SCR and to delay development relative to the susceptible control NC 6. A seedling bioassay where eggs were allowed to develop to the adult stage repeatedly separated NC 7 from NC 6 based on the percentages of adults that emerged. Results indicate the seedling bioassay should be a reliable method for screening large numbers of peanut genotypes before committing the time, space, and labor required for field evaluations. In addition, future peanut breeding programs should consider attempting to introduce the resistance expressed in NC-GP WS 9, N92069L, and N97059N into lines with desirable agronomic characteristics.

Infection ofFrankliniella fusca(Thysanoptera: Thripidae) in Peanut by the Parasitic NematodeThripinema fuscum(Tylenchidae: Allantonematidae)

Frankliniella fusca (Hinds) is a species of thrips that is a pest of peanuts and an important vector of tomato spotted wilt virus. In previous research, populations of thrips declined in peanut during midseason for unexplained reasons. Nematodes in the genus Thripinema are parasites of thrips that render infected females sterile. A new species, T. fuscum Tipping & Nguyen, was recently described as a parasite of F. fusca in peanut. In 1997 and 1998, the temporal changes in percent parasitism of F. fusca in plots of peanuts were determined. Parasitism of adult female thrips increased from an estimated 1% on seedling peanut each year to a maximum of 68% later in the 1997 growing season and 38% in the 1998 growing season. Treatments of several insecticides for control of thrips reduced percent parasitism of the females on most sample dates in 1997, but parasitism was not significantly affected in 1998. Estimates of the numbers of F. fusca in the flowers and terminal buds of peanuts declined each year as parasitism increased. The very high levels of parasitism in 1997 were associated with near extinction of larval populations of thrips during midseason. As a result, the spread of tomato spotted wilt virus by this vector species was reduced. Thus, T. fuscum may be an important natural enemy of F. fusca responsible for suppression of populations of thrips in peanut.

Expression of Nematode Resistance in Plant Introductions of Arachis hypogaea

Abstract The peanut root-knot nematode (Meloidogyne arenaria, race 1) is a world-wide pest of peanut (Arachis hypogaea L.). Several moderately resistant genotypes have been identified in the cultivated peanut species. Our objective was to determine the expression of resistance for six of these genotypes. We examined four potential expressions of resistance—(a) fewer second-stage juveniles (J2) penetrate the roots, (b) fewer J2 establish functional feeding sites, (c) slower maturation, and (d) reduced fecundity (eggs per female). Seedlings of the susceptible cultivar Florunner and the resistant genotypes were inoculated with J2 of M. arenaria, and transplanted 3 d later to synchronize nematode development. Penetration was assessed at 3 and 10 d; development at 10 (or 12), 17, 22, and 27 d; and fecundity at 60 d after inoculation. The experiments were conducted in a greenhouse or growth chamber. The number of J2 within the roots was similar in resistant and susceptible peanut after 3 d; however, numbers were lower in two of the resistant genotypes than in Florunner after 10 d. A greater percentage of J2 failed to develop in all of the resistant genotypes (72 to 79%) than in Florunner (50%) after 17 d. Of the J2 that did begin to develop, the rate of maturation and fecundity was similar in resistant and susceptible genotypes. A lack of development indicates that the J2 failed to establish a feeding site. Therefore, the primary expression of resistance in the six peanut genotypes appears to be a reduction in the percentage of J2 that establish a functional feeding site. The decline in J2 after infection may be related to the failure to establish a feeding site.

Temperature-Dependent Developmental Models for Predicting the Phenology of Maladera matrida (Coleoptera: Scarabaeidae)

Maladera matrida Argaman is a key pest of peanuts ( Arachis hypogaea L.) in Israel. The ability to predict accurately the occurrence of different developmental stages of this beetle may facilitate and improve the control of population of this pest. Thus, 4 non linear (logistic, exponential, sigmoid, and biophysical) models and 1 linear model were tested to fit the relationship between the developmental rate of M. matrida and temperature in a wide range of constant temperatures (20–31 ± 1°C). The required degree-days and the developmental threshold were estimated from the linear portion of the biophysical model, which provided the best fit to the developmental rate data generated in the laboratory. A linear phenological model using the parameters derived from the biophysical model accurately predicted the developmental time of the early generation of M. matrida in peanut fields but failed to predict developmental time of later generations. Predictive extension timing estimation (PETE), a time varying distribution delay model, accurately predicted the occurrence of both early and late generations. It is critical for growers to be able to predict the occurrence of 1st instars in the soil of germinating peanut fields following the emergence of the pest after overwintering. This information allows peanut growers to be prepared with monitoring and control devices to reduce the damage caused by M. matrida to peanuts.

Effects of Ozone on Reproduction of Twospotted Spider Mite (Acari: Tetranychidae) on White Clover

Twospotted spider mite, Tetranychus urticae Koch, is a significant pest of peanut, Arachis hypogeae L., that continues to present problems as an induced pest despite recent widespread implementation of IPM practices. Effects of ozone (O3) on reproduction of twospotted spider mites feeding on an O3-sensitive clone and an O3-resistant clone of white clover, Trifolium repens L., were investigated in a greenhouse in continuous-stirred tank reactor chambers. Mite eggs of narrow age distribution (approximately 6 h) were placed on white clover plants exposed to 5 treatment levels of O3. Constant amounts of O3 were added to charcoal-filtered air for 6 h per day to achieve 5 mean concentrations ranging from 10 to 112 nl per liter. Plants were exposed to O3 approximately 9 d before infestation with mites; daily exposures continued for approximately 20 d after mite infestation. The developmental stage of each mite was recorded at approximately 2-d intervals until females were sexually mature (approximately 10 d) and began ovipositing. Thereafter, the cumulative number of eggs produced per mite was recorded. After approximately 5 d of oviposition, each adult mite was removed and the percentage hatch of eggs remaining on each plant was measured for an additional 5 d. Ozone caused more chlorosis and necrosis on the O3-sensitive clover clone than on the O3-resistant clover clone. Increasing O3 levels caused a significant linear decrease in developmental period of the mites. Estimates of time to 1st oviposition decreased linearly with increasing O3. Estimates of time of 1st hatch of 2nd-generation eggs decreased linearly with increasing O3. Elevated O3 levels appear to decrease the time required for female mites to develop from egg to ovipositing adult, which may have a profound effect on the intrinsic rate of population increase. Different responses by mites feeding on resistant plants versus susceptible plants suggests that this is a plant-mediated response.

A Risk Index for Determining Insecticide Treatment for Southern Corn Rootworm in Peanut

Abstract The southern corn rootworm, Diabrotica undecimpunctata howardi Barber, is a primary pest of peanut, Arachis hypogaea L., in Virginia and North Carolina and an occasional pest in South Carolina, Georgia, Alabama, and Texas. Currently, no alternatives involving integrated pest management exist for this pest, and control is based solely on preventive application of soil insecticides. Recent reductions in federal price support for peanut grown in the U.S. have provided incentives for growers to look for ways to reduce production costs. A risk index was developed that integrates factors that influence rootworm abundance and peanut pod damage to estimate levels of risk in individual peanut fields, and thus allows for more prescriptive and economical rootworm management. This index was evaluated using 44 field case studies in Virginia and North Carolina commercial peanut fields over the period 1989 to 1996. In each field case, predicted risk was compared to actual percent pod damage. Results showed that in 29 of 44 cases, the index accurately predicted general levels of risk to pod damage, and insecticide treatment decisions based on the index would have been correct in 32 of 44 cases. This report contains the individual index components, the justification for each, the indexing process, example index scenarios, and results of the process used in field case study evaluation.

Laboratory and Field Evaluations of Virginia-Type Peanut Genotypes for Resistance toDiabrotica undecimpunctata howardiBarber (Coleoptera: Chrysomelidae)

Abstract The southern corn rootworm (Diabrotica undecimpunctata howardi Barber) is the primary soil insect pest of peanut (Arachis hypogaea L.) in Virginia and North Carolina. The majority of acreage is planted to recently released cultivars which have not been extensively screened for rootworm resistance. The objectives of this study were to evaluate five virginia-type cultivars (NC-V 11, VA-C 92R, VA 93B, NC 10C, and AgraTech VC-1) and 19 breeding lines for resistance to southern corn rootworm and develop efficient resistance laboratory and field screening techniques for peanut. Laboratory-grown seedlings and pegs, and immature and mature pods taken from field-grown plants were used in bioassays. Neonates from a laboratory colony were reared to the adult stage on plant tissues and evaluated for mortality. Pod damage was determined from field studies where plants were exposed to natural southern corn rootworm infestations. With seedling feeding, NC 6 resulted in significantly more rootworm mortality as c...

Evaluation of Peanut Breeding Lines for Resistance to Silverleaf whitefly (Homoptera: Aleyrodidae)

Silverleaf whitefly, Bemisia argentifolii Bellows & Perring, n. sp., is a new and occasionally damaging pest of peanut, Arachis hypogaea L., in Florida and other southern states. In 1992 and 1993, elite germplasm from the peanut breeding program at the University of Florida and several commercial cultivars were evaluated for resistance to silverleaf whitefly. In 1992, 52 genotypes that were chosen based on their performance in previous trials were evaluated. Numbers of whitefly red-eyed nymphs on peanut genotypes differed significantly. However, only two genotypes supported fewer whiteflies (although not significantly) than the cultivar ‘Southern Runner’. In 1993, we evaluated selections of crosses between Florida parent material (81206 and 567A) and a North Carolina parent (GP-NC343) with multi-insect resistance. All selections tested had higher numbers of whitefly eggs and red-eyed nymphs than either ‘Florunner’ or ‘Southern Runner’. No resistance to silverleaf whitefly was found in the peanut germplasm tested.

Population Levels and Parasitism of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) on Peanut Cultivars

Sweetpotato whitefly, Bemisia tabaci (Gennadius), has recently become a pest of peanut in the southern United States. Limited observations in grower fields had identified differences in infestation among cultivars. We wished to determine whether selected cultivars grown commercially in this region resisted whitefly infestation and whether parasitism by aphelinid parasitoids differed among cultivars. Five cultivars were evaluated in summer 1992 and six in summer 1993. In 1992, ‘Florunner’ supported the greatest populations of red-eye nymphs and ‘Southern Runner’ supported the lowest populations. Encarsia nigricephala Dozier was the most common parasitoid (53.0% of all parasitoids reared), followed by Encarsia transvena (Timberlake) (25.6%), and Encarsia pergandiella Howard (18.3%). Parasitism was uniformly high and species composition on the five cultivars did not differ. In 1993, ‘Southern Runner’ supported the greatest populations of all immature whitefly stages except red-eye nymphs. ‘Marc I’ supported the lowest levels of whitefly infestation. E. nigricephala was extremely abundant in 1993 (85.3% of all parasitoids reared), followed by E. pergandiella (9.8%), and E. transvena (4.7%). Eretmocerus nr. californicus was found in low numbers in both years. Again, in 1993, parasitism was high on all cultivars (up to 100% by the end of September), and no differences were noted in the parasitoid composition among the six cultivars. Whitefly infestation was light in these noninsecticide-treated peanut plots, most likely because of natural control by native aphelinid parasitoids, and other beneficial insects.

Effects of Two Cropping and Two Tillage Systems and Pesticides on Peanut Pest Management1

Abstract In one or more years of a 3-year study, white mold (Sclerotium rolfsii) and Rhizoctonia limb rot (Rhizoctonia solani) damaged peanuts less in a wheat-peanut than in the fallow-peanut cropping system, but velvetbean caterpillar (Anticarsia gemmatalis) damage was less in the fallow-peanut. Thrips (Frankliniella fusca) and Rhizoctonia limb rot damage was less in minimum tillage than in conventional tillage but root-knot nematode (Melodogyne arenaria) damage was less in conventional tillage. Aldicarb reduced root-knot and lesion nematode (Pratylenchus brachyurus), thrips, and potato leafhopper (Empoascafabae) damage, but increased numbers of three cornered alfalfa hoppers (Spissistilus festinus) and velvetbean caterpillar damage. Flutolanil reduced white mold and Rhizocotonia limb rot damage. There was a high negative correlation (P=0.0001) of number of white mold loci with yield (r=-0.70). Rhizoctonia limb rot, gall and lesion indices and number of lesion nematodes in the soil were also negatively correlated with yield, but at low levels. Cropping systems did not affect peanut yields; however, tillage systems and nematicide/insecticide and fungicide treatments had major effects. Mean yield in conventional-tillage plots were greater than in minimum-tillage plots for the control and each chemical treatment. Mean yields were 11.1%, 55.9%, and 77.3% greater than control of aldicarb, flutolanil, and aldicarb plus flutolanil treatments, respectively, across cropping systems, tillage systems, and years.

Population Suppression of the Almond Moth and the Indianmeal Moth (Lepidoptera: Pyralidae) by Release of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) into Simulated Peanut Storages

A biological control test in simulated peanut storages indicated that release of Trichogramma pretiosum Riley, a parasite of moth eggs, has considerable potential for suppression of stored-product Lepidoptera. Suppression of the almond moth, Cadra cautella (Walker), and the Indianmeal moth, Plodia interpunctella (Hubner), was dependent on numbers of T. pretiosum released and on frequency of releases. Percentage of total population suppression was as much as 41.7%for the almond moth and 57.4% for the Indianmeal moth. Trichogramma spp. may be useful as part of an integrated peanut pest control program based on biological agents.

Root-knot Nematode Resistance in Arachis Glabrata1

Abstract Peanut root-knot nematode (Meloidogyne arenaria race 1) is an important pest of cultivated peanuts (Arachis hypogaea L.). Experimental data do not exist, however, to indicate whether this nematode might be a potential pest of peanuts grown for forage production. Florigraze and Arbrook, two recently released cultivars of rhizoma peanut (Arachis glabrata Benth.) and P.I. 446898 (Arachis spp.) with perennial forage potential, were evaluated for their interaction with M. arenaria race 1, M. javanica, and M. incognita races I and III. Individual plants, grown in 150 cm3 ConetainersR, were inoculated with 3,000 eggs of one of the four Meloidogyne spp. populations. After three months gall and egg mass scores and soil-nematode counts were determined for each plant sample. A second long-term experiment evaluated Florigraze that was repeatedly inoculated with high levels of root-knot nematodes. Both rhizoma peanut cultivars were highly resistant to all root-knot nematodes tested; Florigraze appeared to be immune. P.I. 446898 was intermediate between the rhizoma peanuts and the susceptible alyceclover check. This is the first known report of such high levels of Meloidogyne arenaria resistance in Arachis spp. Further screending of A. hypogaea material can be justified based on these results and Vavilov's “Law of homologous series”. If no resistance is found in A. hypogaea, A. glabrata may provide a source of resistance that may be transferred to A. hypogea through hybridization.

Estimating and Evaluating Economic Losses by White-Fringed Beetles on Peanuts

White-fringed beetles (WFB), Graphognathus spp., have been described as “potentially one of the worst pests of peanuts in the southeastern United States” (Bass and Arant 1972). WFB larvae have been recognized as a destructive pest of peanuts in the southeastern United States for more than 25 years (Arant 1951). After their discovery in the Florida Panhandle in 1936, the insect spread rapidly throughout the Southeast despite quarantine efforts (Henderson and Padgett 1948). Because most damage is done by the larva, its control is critical. Various insecticides and other control methods were tried since 1936, but the most effective controls were those that killed the larvae in the soil. The most effective, commonly used insecticides were DDT, aldrin, dieldrin, and chlordane. All these had relatively long residual toxicity when incorporated into the soil and could provide WFB control for several years (Hollingsworth and Young 1961). Other possible soil insecticides were tested in 1971 and 1972, but treatment with these did not result in any significant increase in yield (Harlan and Gross 1976).

Pest Status of Pangaeus bilineatus Attacking Peanuts in Texas12

Pangaeus bilineatus (Say) recently became a major pest of peanuts in the southern peanut production area of Texas, where losses from this pest were first recorded in 1968. Pod feeding by adults and nymphs resulted in an undesirable discoloration of peanut kernels. Losses in quality in Frio County in experimental plots were as high as $184.11/ton. Observations of natural enemies revealed only 1 parasite, Triozocera mexicana Pierce, and 1 predator, Solenopsis xyloni McCook. Other cydnids found in peanut fields were P. congruus (Uhler) and Cyrtomenus ciliatus (Palisot de Beauvois).

Suppression of the Two-Spotted Spider Mite on Peanuts1

Abstract The two-spotted spider mite, Tetranychus urticae Koch, is a major pest of peanuts in North Carolina. Mite populations increase during hot, dry weather and are especially destructive in August and September. The potential losses to peanuts due to mites prompted an investigation of the miticidal and ovicidal properties of fungicides and insecticides currently registered for peanuts as well as the evaluation of chemicals not registered on peanuts for control of the two-spotted spider mite. Plictran, Galecron, Trithion, Azodrin, Carzol, and Omite provided good suppression of the spider mite in field tests. Laboratory studies, using a five second dip technique, indicated Plictran, Galecron, and Trithion had good ovicidal properties. The fungicides Du-Ter and Benlate exhibited a low level of ovicidal action. Du-Ter recommended for leaf spot control gave good control of mites in the laboratory tests and suppressed mite buildup in greenhouse experiments.

Rearing Technique for the Granulate Cutworm1 and Some Effects of Temperature on Its Life Cycle

The granulate cutworm, Feltia subterranea (F.), is commonly found in the southern United States. It feeds on a wide variety of plants, and during the past several years it has been a major pest of peanuts in Alabama and Georgia.