Plathypena Scabra Research Articles

Spatial Associations of Key Lepidopteran Pests With Defoliation, NDVI, and Plant Height in Soybean

In soybean, Glycine max (L.) Merrill, production, losses to, and control costs for insect pests can be significant limiting factors. Although the heterogeneity of pests has typically been ignored in traditional field management practices, technological advancements have allowed for site-specific pest management systems to be developed for the precise control of pests within a field. In this study, we chose to determine how the in-field distributions of the larvae of three major lepidopteran pests [velvetbean caterpillar Anticarsia gemmatalis (Hübner) (Lepidoptera: Erebidae), soybean looper Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), and green cloverworm Hypena scabra (Lepidoptera: Erebidae) (Fabricius)] were spatially associated with defoliation, Normalized Difference Vegetation Index (NDVI), and plant height in soybean. Spatial analysis by distance indices (SADIE) of data from two South Carolina soybean fields in 2017 and 2018 revealed a limited number of spatial aggregations for insect datasets. However, 14% and 6% of paired plant-insect datasets were significantly associated or dissociated, respectively. NDVI was found to be more associated with pest distributions than soybean plant heights and defoliation estimates, and the majority of all plant-insect associations and dissociations occurred in the first 4 wk of sampling (late July-early August). If changes are to be implemented regarding how a pest is managed, critical factors explaining the spatial distribution of pests must be identified. Results from this study advocate for the relationship between early-season distributions of pests and important plant variables such as NDVI to be further investigated to better determine the strength of the correlations across years and sites.

Associating Site Characteristics With Distributions of Pestiferous and Predaceous Arthropods in Soybean.

Although site-specific pest management has the potential to decrease control costs and environmental impact associated with traditional pest management tactics, the success of these programs relies on the accurate characterization of arthropod distributions within a crop. Because potential correlation of insect counts with remotely sensed field attribute data could help to decrease the costs associated with and need for fine-scale spatial sampling, we chose to determine which within-field variables would be informative of soybean arthropod counts in an attempt to move toward site-specific pest management in this crop. Two soybean fields were grid-sampled for pestiferous and predaceous arthropods, plant productivity estimates, and abiotic variable characterization in 2017-2018. Negative binomial, zero-inflated models were used to estimate presence and counts of soybean arthropod taxa based on normalized difference vegetation index (NDVI), soybean plant height, soil electrical conductivity (ECa), elevation, and calendar week. Among all variables, calendar week was the most reliable predictor of arthropod counts, as it was a significant predictor for a majority of all taxa. Additionally, counts for a majority of pestiferous taxa were significantly associated with distance from the field edge, elevation, soybean plant height, and NDVI. Although site-specific pest management has the potential for reduced management inputs and increased profitability over conventional management (i.e., whole-field) practices, management zones must first be clearly defined based on the within-field variability for the variables of interest. If site-specific pest management practices are to be applied in soybean, calendar week (and associated soybean phenology), soybean plant height (and associated elevation), and NDVI may be useful for describing the distributions of pests, such as kudzu bug, Megacopta cribraria (Hemiptera: Plataspidae) (Fabricius), green cloverworm, Hypena scabra (Lepidoptera: Erebidae) (Fabricius), velvetbean caterpillar, Anticarsia gemmatalis (Lepidoptera: Erebidae) (Hübner), and soybean looper, Chrysodeixis includens (Lepidoptera: Noctuidae) (Walker).

Current Distribution and Population Persistence of Five Lepidopteran Pests in U.S. Soybean

AbstractThe distribution of lepidopteran pests in soybean (Glycine max (L.) Merr.) is a current knowledge gap limiting accurate prioritization of Integrated Pest Management (IPM) research. Regional characterizations of lepidopteran distribution in soybean are now more than 25 yr old. The goal of this study was to generate a contemporary assessment of the distribution and population persistence of lepidopteran soybean pests. To understand which species are currently infesting soybean and their persistence, we conducted a survey of soybean entomologists with responsibility for approximately 33.6 million hectares of production in 31 U.S. states. Soybean entomologists were asked questions about presence of lepidopteran pests and their persistence in their state. We focused this survey on five lepidopteran pests: corn earworm (Helicoverpa zea Boddie) (Lepidoptera: Noctuidae), green cloverworm (Hypena scabra Fabricius) (Lepidoptera: Erebidae), painted lady (Vanessa cardui L.) (Lepidoptera: Nymphalidae), soybean looper (Chrysodeixis includens Walker) (Lepidoptera: Noctuidae), and velvetbean caterpillar (Anticarsia gemmatalis Hübner) (Lepidoptera: Erebidae). Soybean entomologists also provided insight into regionally relevant or sporadic lepidopteran soybean pests. Participants were also questioned about common scouting practices in each state. Results of this survey highlight dissimilar geographic distribution and relative persistence of lepidopteran pests in soybean. Clear differences in occurrence and abundance among species provide important contemporary distributions and persistence estimates. Assessments of scouting practices demonstrate a need to improve IPM adoption in some states. Results of this study and its complementary pest profile (concurrently published in JIPM) provide a contemporary foundation for studies of lepidopteran soybean pests.

Ants Increase Cloverworm Herbivory Via Nonconsumptive Pathways

Generalist arthropod predators often exhibit a range of intraguild interactions reducing their potential efficacy as biological control agents. These interactions may include consumptive or nonconsumptive effects that mediate the impacts of herbivores. We examined interactions among 2 generalist predators, the striped lynx spider (Oxyopes salticus Hentz; Araneae: Oxyopidae) and an ant (Lasius neoniger Emery; Hymenoptera: Formicidae), and a herbivore, the green cloverworm (Hypena scabra F.; Lepidoptera: Erebidae), all prevalent in central Kentucky soybean agroecosystems. We hypothesized that individual predator treatments would reduce green cloverworm survival and resultant leaf damage, but that predators would interfere with each other when both were present. To study these interactions, field cages containing potted soybeans were used to examine 8 treatment combinations (control, cloverworm, spider, ant, spider + cloverworm, ant + cloverworm, ant + spider, and ant + spider + cloverworm). When proportional leaf damage was compared, spider, ant + spider, and spider + cloverworm treatments had significantly less damage than the ant, ant + cloverworm, and ant + spider + cloverworm treatments. Spider presence tended to decrease plant damage while ant presence significantly increased damage. No differences among treatments were found for either spider or cloverworm recovery, indicating potential nonconsumptive effects of ants that may include compensatory feeding. We found that generalist predators, such as L. neoniger, can inhibit biological control due to nonconsumptive interactions even when the same species in a different system provides substantial levels of pest suppression. Resumen Los depredadores de artropodos generalistas a menudo exhiben un rango de interacciones intra-gremial (entre el grupo depredador) reduciendo su eficacia potencial como agentes de control biologico. Estas interacciones pueden incluir efectos consuntivos o no consuntivos que median los impactos de los herbivoros. Examinamos las interacciones entre dos depredadores generalistas, la arana lince rayada (Oxyopes salticus Hentz; Araneae: Oxyopidae) y una hormiga (Lasius neoniger Emery; Hymenoptera: Formicidae), y un herbivoro, el gusano verde de trebol (Hypena scabra F.; Lepidoptera: Erebidae), todos prevalentes en los agroecosistemas de soja del centro del estado de Kentucky. Presumimos que los tratamientos de depredadores individuales reducirian la sobrevivencia del gusano verde de trebol y el dano resultante en las hojas, pero que los depredadores interferirian entre si cuando ambos estuvieran presentes. Para estudiar estas interacciones, se utilizaron jaulas de campo que contenian soja en maceta para examinar 8 combinaciones de tratamiento (el control, el gusano verde de trebol, arana, hormiga, arana + el gusano verde de trebol, hormiga + el gusano verde de trebol, hormiga + arana, y hormiga + arana + el gusano verde de trebol). Cuando se comparo el dano proporcional de las hojas, los tratamientos de arana, hormiga + arana y arana + el gusano verde de trebol tuvieron un dano significativamente menor que los tratamientos de hormiga, hormiga + el gusano verde de trebol y hormiga + arana + el gusano verde de trebol. La presencia de las aranas tiende a disminuir el dano a las plantas, mientras que la presencia de las hormigas aumenta significativamente el dano. No se encontraron diferencias entre los tratamientos para la recuperacion de la arana o el gusano verde de trebol, lo que indica posibles efectos no consuntivos de las hormigas que pueden incluir la alimentacion compensatoria. Descubrimos que los depredadores generalistas, como L. neoniger, pueden inhibir el control biologico debido a interacciones no consumidoras, incluso cuando la misma especie en un sistema diferente proporciona niveles sustanciales de supresion de plagas. Key Words: Hypena scabra; field cage; food web; Lasius neoniger; Oxyopes salticus View this article in BioOne

Nature of Damage and Infestation of Dominant Foliage Herbivore of Soybean at Jimma-Iluababora, Ethiopia

Leaf herbivore insects are among the most serious pests of soybean in Ethiopia. A survey was conducted on 90 farms in three main soybean growing districts in Jimma and Iluababora zones of Ethiopia. The objectives were to assess the socio demographic information of the farmers, to identify farmers’ pest management practices and to study the importance and infestation of dominant leaf herbivore insect pests of soybean. The statistical analysis showed there is highly significant (p<0001) difference among studied districts in area coverage of soybean production and the majority of the farmers (81.1%) produce soybean below a hectare. Farmers were using different pest management methods to reduce damage caused by leaf phaga insect pests which concentrated on cultural method. Crop rotation was one of the main farming systems practiced by 80% at Tiroafeta and 96.7 and 100 % at Chewaka and Darimu districts. About 16.7% farmers of Tiroafeta were not practiced any management practices for pest management where as only 3.3 % of them practiced manually hand picking method at Chewaka. At Darimu district, all surveyed farmers did not get any access to crop protection training, but at Tiroafeta and Chewaka only 3.3 % of them got training opportunity provided by research center. The study revealed that the mean infestation level of green clover worm was 29.8 % at Tiroafeta district and 47 and 50.4 % at Chewaka and Darimu. The mean infestation of soybean semilooper was 25.3 % at Tiroafeta and 14.6 and 15.6 % at Chewaka and Darimu districts. The study showed that infestation of soybean leaf roller ranged from 2.5 to 8.2 % in Jimma zone and up to 74 % in Iluababora. Generally, these insect pests, needs due attention conducting regular scouting in unaddressed areas are very important for integrated pest management. Keywords: Green cloverworm, infestation, leaf roller, semi-looper, soybean DOI: 10.7176/JEES/10-7-02 Publication date: July 31 st 2020

Effects of aphid-resistant soybean on nontarget herbivores in Minnesota

The use of aphid-resistant soybean varieties containing Rag genes can provide an effective pest management strategy against soybean aphid (Aphis glycines Matsumura). However, the compatibility between soybean containing Rag genes and the management of other potential soybean pests (i.e., nontarget herbivores) is poorly understood. Therefore, our goal was to (1) assess the efficacy of pyramided (Rag1+Rag2) aphid-resistant soybean for reduction of soybean aphid populations, and (2) determine if aphid-resistant soybean affects populations of nontarget herbivores under field conditions. To accomplish these goals, field experiments were conducted in southeast Minnesota from 2015 to 2017 for a total of five site-years using whole-plant counts to assess soybean aphid densities and sweep-net sampling to estimate nontarget herbivore densities in plots of near-isoline soybean with Rag1+Rag2 (i.e., resistant) or no Rag genes (i.e., susceptible). Plant genotype (i.e., resistant or susceptible) affected seasonal abundance of soybean aphid, with fewer soybean aphids on aphid-resistant than susceptible soybean. Furthermore, plant genotype affected seasonal abundance of bean leaf beetle (Cerotoma trifurcata Forster), green cloverworm (Hypena scabra Fabricius), and potato leafhopper (Empoasca fabae Harris). Aphid-resistant soybean was associated with increased seasonal abundance of bean leaf beetle and reduced seasonal abundance of potato leafhopper and green cloverworm. The abundance of these herbivores was also associated with seasonal abundance of soybean aphid as a covariate. Results presented here confirm the efficacy of aphid-resistant soybean with Rag1+Rag2 against soybean aphid and show that aphid-resistant soybean can influence the seasonal abundance of nontarget herbivores in soybean. However, the magnitude of impacts of aphid-resistant soybean on nontarget herbivores was relatively small and likely of little-to-no agronomic significance, which suggests compatibility of aphid-resistant soybean with management of other potential pests.

Evaluation of Pest Vulnerability of ‘Benning’ Soybean Value Added and Insect Resistant Near Isogenic Lines

Crop enhancement with value added traits may affect vulnerability to insects, and evaluating the susceptibility levels of the various value added traits in elite germplasm would aid in developing integrated pest management strategies. During 2007-2008, five 'Benning' soybean (Glycine max (L.) Merr) lines with different value added nutritional traits and four insect resistant quantitative trait loci (QTL) lines were evaluated in an effort to determine their pest vulnerability under artificial and natural insect pest populations. The lines showed variable susceptibility to lepidopterous insect pests classified as defoliators and stem feeders in replicated greenhouse and field tests. The study was carried out in Athens and Midville, GA. The green cloverworm (Hypena scabra (F.)) was the most common lepidopteran defoliator occurring in the fields. Other caterpillar pests found included the soybean looper (Pseudoplusia includens (Walker)), the bollworm (Helicoverpa zea (Boddie)), and the velvetbean caterpillar (Anticarsia gemmatalis (Hübner)). Data indicated that there was no significantly increased pest susceptibility among the value added cultivars with improved nutritional qualities, with the insect resistant quantitative trait loci lines Benning M and Benning MGH consistently being less susceptible to lepidopterous (Noctuidae) leaf injury.

Evaluation of Transgenic Soybean Exhibiting High Expression of a Synthetic &lt;I&gt;Bacillus thuringiensis cry1A&lt;/I&gt; Transgene for Suppressing Lepidopteran Population Densities and Crop Injury

Several transgenic lines of soybean, Glycine max (L.) Merr., expressing a synthetic cry1A gene from Bacillus thuringiensis (Bt), were examined in replicated field trials in 2003-2007 for suppression of naturally occurring population densities of lepidopteran pests and the resultant crop injury that they caused. Bt soybean and negative controls (isogenic segregants and parental lines) were evaluated against velvetbean caterpillar, Anticarsia gemmatalis (Hübner); soybean looper, Pseudoplusia includens (Walker); and green cloverworm, Hypena scabra (F.). Population densities of these lepidopteran species were essentially absent in each of the Bt soybean entries evaluated throughout the growing season in every year of the study compared with moderate (5-10 larvae per row-m) to large (20-30 larvae per row-m) peak population densities in the negative control soybean entries. These lepidopteran populations caused significant plant injury in the non-Bt soybean plots, ranging from 53% defoliation in 2003 to 17.5% in 2007, compared with < 1.5% defoliation (mostly 0.0% defoliation) in the Bt soybean plots. When two or three foliar insecticides were applied in August or September, as lepidopteran populations approached or exceeded economic threshold levels, pest populations were suppressed and defoliation was minimal in the treated non-Bt entries similar to results in Bt soybean. Soybean 100-seed weights and harvested yields were similar between the Bt and non-Bt entries each year of this study. It seems that Bt transgenic soybean provides excellent season-long control of lepidopteran pests and have yields equal to the standard cultivars examined in this study. Once available to producers, this Bt technology has the potential to provide an effective insect pest management option similar to that being used in Bt cotton, Gossypium hirsutum L., and Bt corn, Zea mays L., and enhance the sustainability and profitability of soybean production in the southern region where lepidopteran pests cause annual economic losses to the crop.

Assessing Lepidopteran Abundance and Crop Injury in Soybean Lines Exhibiting a Synthetic Bacillus thuringiensis cry1 A Gene

Transgenic lines of soybean, Glycine max (L.) Merrill, expressing a synthetic cry 1A gene from Bacillus thuringiensis Berliner (Bt), were evaluated in replicated field trials in 1999–2002 for suppression of lepidopteran pests and the resultant crop injury. Velvetbean caterpillar, Anticarsia gemmatalis Hübner, soybean looper, Pseudoplusia includens (Walker), and green cloverworm, Hypena scabra (F.), population densities were essentially absent throughout the growing season in each year of the study in each of the Bt lines evaluated compared with moderate (5–10 larvae per row-m) to heavy (15–20 larvae per row-m) populations in the isogenic and parental lines serving as soybean controls. Significant A. gemmatalis larval population reductions were observed in the Bt entries compared with the nonBt entries in each year of this study. The P. includens larval densities were significantly lower in Bt entries in the 3 yrs of this study when population densities were abundant, whereas H. scabra were lower in the Bt lines in the 2 yrs of this study when this species was present. Cumulative defoliation in nonBt soybean entries exceeded 95% in some years compared with 0.0–1.6% in the transgenic lines containing Bt. Yields of the transgenic soybean lines were equal to or higher than the non Bt lines examined in each year of this study. It appears that these Bt transgenic soybeans provide superior season-long control of the common lepidopteran pests on soybeans in the southern U.S., resulting in reduced defoliation levels and potentially higher yields compared with equivalent cultivars that lack the Bt trait.

The role of host plant species in the phenotypic differentiation of sympatric populations of Aleiodes nolophanae and Cotesia marginiventris

AbstractThe ecology of parasitoids is strongly influenced by their host plant species. Parasitoid fitness can be affected by a variety of plant traits that could promote phenotypic differentiation among populations of parasitoids. Generalist parasitoids are expected to be more affected by plant traits (e.g., plant defensive traits) than specialist parasitoids. Data are presented on phenotypic differences of two braconid parasitoid wasps ovipositing on the same insect host species on two different host plant species. Adult mass, adult longevity, and percent parasitism are compared for the generalist parasitoid Cotesia marginiventris Cresson and the specialist parasitoid Aleiodes nolophanae Ashmead (both Hymenoptera: Braconidae) emerging from green cloverworms, Hypena scabra Fabricius (Lepidoptera: Noctuidae), feeding on two host plant species, alfalfa (Medicago sativa L.) and soybean (Glycine max L. Merr.) (both Fabaceae), at three locations. Specialist wasps that parasitized the green cloverworm on alfalfa had a significantly larger mass than the ones that parasitized the green cloverworm on soybean at the three study sites. Generalist wasps that parasitized green cloverworms on alfalfa had a larger mass than wasps parasitizing green cloverworms on soybean only at one of the study sites (i.e., Prince George's County, MD, USA). Similarly, both specialist and generalist wasps lived longer when parasitizing green cloverworms on alfalfa than when parasitizing them on soybean at only one of the study sites (i.e., Prince George's County). In Prince George's County, percent parasitism on alfalfa by the specialist parasitoid was higher than on soybean for three consecutive years and percent parasitism by the generalist parasitoid was the same on alfalfa and soybean every year. Thus, phenotypic differences among populations associated with different host plant species vary geographically (i.e., parasitoid phenotype associated with different host plant species differ at some sites while it is the same at other sites). The implications of geographic variation for biological control are discussed.

Insect Pests and Yield Potential of Vegetable Soybean (Edamame) Produced in Georgia

A series of replicated field experiments was conducted with vegetable soybean (edamame), Glycine max (L.) Merrill, to assess the impacts of cultivars, planting dates, and insecticidal controls on insect pest abundance, crop damage and yield potential. The velvetbean caterpillar, Anticarsia gemmatalis Hübner, was the most common lepidopteran defoliator in this study, causing heavy defoliation in some years when left untreated. Other lepidopterans observed included the soybean looper, Pseudoplusia includens (Walker), and the green cloverworm, Hypena scabra (F.). Stink bugs, primarily the southern green stink bug, Nezara viridula (L.), also caused seed damage in some cultivars when left untreated. Stink bug damage exceeded expectations on edamame seeds when exposed to moderate stink bug densities (≤3 bugs per 25 sweeps). Other arthropods that were commonly observed included threecornered alfalfa hoppers, Spissistilus festinus (Say), grasshoppers, Melanoplus spp., and the potato leafhopper, Empoasca fabae (Harris). Arthropod infestations on edamame were similar to reported pest problems on conventional soybeans being produced for oil and meal. Midseason applications of the insecticides diflubenzuron plus l-cyhalothrin reduced insect pest populations, percentage of arthropod-induced defoliation and percentage of seeds damaged by stink bugs, but had little effect on edamame yields. Most defoliation and seed damage occurred during R5 development when seeds were approaching full size, thus only minimal yield reductions were noted. However, seed quality of the untreated vegetable soybeans would be unacceptable for the consumer. Total fresh green yields ranged from 2343–11,895 kg ha−1, depending on year, cultivar and planting date, whereas fresh green seed yields ranged from 1208–6,119 kg ha−1. Early-maturing edamame cultivars planted in April had fewer insect pests and less damage than the cultivars planted later. Avoidance of insect pests is an important production consideration for insect management, especially critical in an organic production system. The fresh green seed yields produced during this study demonstrate that this emerging alternative crop has the potential for economic success in the southern region, assuming that the arthropod pests are effectively managed to maintain acceptable edamame quality and yield.

Evaluating Lepidopteran Defoliation Resistance in Soybean Breeding Lines Containing the Stink Bug (Hemiptera: Pentatomidae) Resistance IAC-100 Cultivar in Their Pedigrees

Sixty-five soybean, Glycine max (L.) Merrill, breeding lines containing 'IAC-100' in their pedigrees were evaluated for their resistance to lepidopteran defoliation in replicated field trials during 2001-2005. Three soybean cultivars, IAC-100 (with resistance to stink bug [Hemiptera: Pentatomidael feeding), 'Dillon', and 'Hutcheson', also were included in the evaluations. The percentage defoliation among these 68 entries ranged from 4.3 to 28.3% in 2001 and from 35.0 to 99.0% in 2002. Lepidopteran caterpillars, primarily Anticarsia gemmatalis Hiibner, but also some Pseudoplusia includens (Walker) and Hypena scabra (F.), peaked at 14.3 per row-meter on 11 September 2001 and at 39.7 per row-meter on 22 August 2002. Twenty-six entries with better resistance potential, plus two cultivars, were selected for continued evaluations in 2003 and 2004. Defoliation ranged from 23.3 to 56.7% among the 28 entries in 2003 and from 16.3 to 42.5% in 2004, with peak caterpillar densities of 20.3 per row-meter on 17 September 2003 and 14.5 per row-meter on 8 September 2004. From these differential responses, 12 entries were included for advanced resistance evaluations in 2005. The breeding line entries 52 (IAC-100 X V89-1301), 23 (IAC-100 X V89-1301), and 14 (IAC-100 X V71-370), plus entry 37 (IAC-100) had lower defoliation rankings during all 5 yr of this study, with the entry having the lowest defoliation ranked 1 and the entry with highest defoliation ranked either 68, 28, or 12, based on the number of entries evaluated each year. The overall mean rankings of these four entries over the 5 yr of this study were 4.4, 3.0, 4.2, and 4.6, respectively. A fifth entry, 30 (IAC-100 x V71-370), was in the top group with lower defoliation in 4 yr of this 5-yr study, and it had an overall mean ranking of 5.6. A sixth entry, 35 (Hutcheson X IAC-100), had moderate resistance (overall ranking of 19.2) compared with the standard Hutcheson (30.8 ranking of a possible highest ranking of 40.8). Entry 35 also yielded as well as the standard cultivars evaluated in the study. These lines will provide excellent sources for future soybean germplasm and varietal resistance development.

Evaluating Lepidopteran Defoliation Resistance in Soybean Breeding Lines Containing the Stink Bug (Hemiptera: Pentatomidae) Resistance IAC-100 Cultivar in Their Pedigrees

Sixty-five soybean, Glycine max (L.) Merrill, breeding lines containing ‘IAC-100′ in their pedigrees were evaluated for their resistance to lepidopteran defoliation in replicated field trials during 2001–2005. Three soybean cultivars, IAC-100 (with resistance to stink bug [Hemiptera: Pentatomidae] feeding), ‘Dillon’, and ‘Hutcheson’, also were included in the evaluations. The percentage defoliation among these 68 entries ranged from 4.3 to 28.3% in 2001 and from 35.0 to 99.0% in 2002. Lepidopteran caterpillars, primarily Anticarsia gemmatalis Hübner, but also some Pseudoplusia includens (Walker) and Hypena scabra (F.), peaked at 14.3 per row-meter on 11 September 2001 and at 39.7 per row-meter on 22 August 2002. Twenty-six entries with better resistance potential, plus two cultivars, were selected for continued evaluations in 2003 and 2004. Defoliation ranged from 23.3 to 56.7% among the 28 entries in 2003 and from 16.3 to 42.5% in 2004, with peak caterpillar densities of 20.3 per row-meter on 17 September 2003 and 14.5 per row-meter on 8 September 2004. From these differential responses, 12 entries were included for advanced resistance evaluations in 2005. The breeding line entries 52 (IAC-100 × V89-1301), 23 (IAC-100 × V89-1301), and 14 (IAC-100 × V71-370), plus entry 37 (IAC-100) had lower defoliation rankings during all 5 yr of this study, with the entry having the lowest defoliation ranked 1 and the entry with highest defoliation ranked either 68, 28, or 12, based on the number of entries evaluated each year. The overall mean rankings of these four entries over the 5 yr of this study were 4.4, 3.0, 4.2, and 4.6, respectively. A fifth entry, 30 (IAC-100 × V71-370), was in the top group with lower defoliation in 4 yr of this 5-yr study, and it had an overall mean ranking of 5.6. A sixth entry, 35 (Hutcheson × IAC-100), had moderate resistance (overall ranking of 19.2) compared with the standard Hutcheson (30.8 ranking of a possible highest ranking of 40.8). Entry 35 also yielded as well as the standard cultivars evaluated in the study. These lines will provide excellent sources for future soybean germplasm and varietal resistance development.

Cropping Preferences of Common Lepidopteran Pests in a Cotton/Soybean Cropping System

Two soybean varieties (an early-maturing Group V and a later-maturing Group VII) and two cotton varieties (a conventional and a transgenic Bacillus thuringiensis Berliner [Bt]) were grown in adjacent replicated large field plots at two locations for 3 growing seasons. The abundance of commonly-observed lepidopteran pests within these two crops was observed weekly throughout each growing season. The green cloverworm, Hypena scabra (F.); soybean looper, Pseudoplusia includens (Walker), and; velvetbean caterpillar, Anticarsia gemmatalis Hübner, preferred soybeans over cotton at all six test sites. The bollworm complex, Helicoverpa zea (Boddie) and Heliothis virescens (F.), preferred soybeans at one site, cotton at two sites, and no crop preference at three sites. There was no difference in the seasonal mean abundance of the pests between the two soybean maturity groups. A few varietal differences were noted on soybeans on specific sampling dates; however, they occurred when insect numbers were low. Population densities approached economic injury levels on both the early and later-maturing soybean varieties. In cotton, the bollworm complex was significantly more abundant in conventional cotton than in Bt cotton. Although soybean loopers are a pest of both crops, soybeans are preferred when they are planted adjacent to cotton. Given this behavioral response, soybeans might serve as a trap crop to attract soybean loopers into a small planting of soybeans and out of the major planting of cotton.

Monitoring Red Imported Fire Ant (Hymenoptera: Formicidae) Foraging Behavior and Impact on Foliage-Dwelling Arthropods on Soybean Produced Under Three Ant Suppression Regimes

The red imported fire ant, Solenopsis invicta Buren, has been reported to contribute to the biological control of key arthropod pests in soybean, Glycine max (L.) Merrill, and other crops. Solenopsis invicta also has been implicated as a major disrupter of biological control and a direct crop pest associated with reduced yields. In 2000 and 2001, fire ant foraging, survival of sentinel lepidopteran eggs and pupae, seasonal abundance of common foliage-dwelling soybean arthropods, and crop yield were assessed under three different fire ant suppression treatments at two test sites in Tift Co., GA. The treatments included an untreated control, hydramethylnon ant bait, and hydramethylnon bait in combination with the broad spectrum insecticide chlorpyriphos. Fire ant foraging was reduced in the chemically-treated plots in comparison to the control, based on fire ant numbers on hot dog baits after a 1-h field exposure in the early morning. Survival of soybean looper, Pseudoplusia includens Walker, eggs in 2000 and corn earworm, Helicoverpa zea Boddie, eggs in 2001 was lower in the untreated plots after a 24-h field exposure, where S. invicta foraging rates were high. Soybean looper pupal survival was 34 and 88% lower on foliage and the ground, respectively, in the control compared to those with reduced fire ant foraging. The seasonal abundance of foliage-dwelling soybean arthropods was primarily unaffected by the fire ant suppressing treatments. However, in 2001, green cloverworms, Hypena scabra F., and spiders were significantly lower (38.6 and 40.5%, respectively) in the chlorpyriphos plus hydramethylnon bait treatment in comparison to the other treatments. Season-long suppression of fire ants had no effect on soybean yield. The results of this study suggest that S. invicta, at naturally-occurring levels, is an active predator on some common soybean lepidopteran pests.

Influence of Roundup Ready Soybean Production Systems and Glyphosate Application on Pest and Beneficial Insects in Narrow-Row Soybean

Roundup Ready® soybeans, Glycine max (L.) Merrill, in narrow-row planting systems were investigated in 1998 in Mississippi to evaluate the effects of the transgenic crop and glyphosate herbicide on pest and beneficial insects. Insects found in sufficient numbers for meaningful analysis included adult bean leaf beetle, Cerotoma trifurcata (Forster); adult three-cornered alfalfa hopper, Spissistilus festinus (Say); adult big-eyed bug, Geocoris punctipes (Say), and; larvae of green cloverworm, Plathypena scabra (F.), and velvetbean caterpillar, Anticarsia gemmatalis (Hübner). Populations of C. trifurcata, S. festinus, P. scabra and A. gemmatalis were not reduced in genetically altered Roundup Ready soybean, or by recommended (by label) or delayed applications of glyphosate. Numbers of G. punctipes also were not reduced in Roundup Ready soybean, but were reduced by recommended applications of glyphosate during weeks three and four following the second recommended herbicide application. Geocoris punctipes densities also were reduced at 1 and 2 wks after the first glyphosate application in plots in which the second application of glyphosate was delayed. Numbers of G. punctipes may have been indirectly reduced by glyphosate within sample weeks two and three because of variations in weed densities after treatment with the herbicide.

EVALUATION OF INSECTICIDES FOR MANAGEMENT OF A LOOPER COMPLEX AND A VELVETBEAN CATERPILLAR - GREEN CLOVERWORM COMPLEX ON SOYBEAN, 2002A

Eight insecticides were evaluated to determine rate effects on Soybean looper (SL), Cabbage looper (CL), Green cloverworm (GCW) and Velvetbean caterpillar (VBC) on soybean. Pre-treatment insect counts revealed that larvae of each species were mainly in midto late instars on day 1 prior to application of the insecticides. Looper infestation consisted of 89% SL and 11% CL at the time the insecticides were applied. Because current identification of the larvae in the field is difficult, especially very small larvae, the number of loopers in samples was combined and reported as a looper complex (SL/CL). This same procedure was used to record the GCW and VBC (GCW/VBC) infestations, both species being about equally susceptible to many insecticides. Plots were located at the Mississippi State University Plant Science Research Farm, Mississippi State, MS. Soybeans were planted on May 29, 2002 in 38-inch rows, using the conventional planting system for soybean in the area. Treatment plots were four rows, 35 ft long, arranged in a randomized complete block design with four replications and a 8-ft alley between replications. Insecticide treatments were applied 8 Aug, using a backpack CO2 sprayer, equipped with eight CONEJET T 3X nozzles, 16 inch apart (2 nozzles per row), delivering 10 gpa at 40 psi, with water as a carrier for the insecticide. Soybeans were in the R5 stage. The environmental conditions at application were 68°F , 100% Rh, with sunshine and wind speed of less than 1 mph. Ground cloth samples were taken from the two middle rows of each plot on days 2 and 7 after spray application. Mean number of larvae in each complex was calculated for each date. Data were analyzed using SAS proc ANOVA, and means were separated using Fisher's least significant differences (LSD).

EVALUATION OF INSECTICIDES FOR MANAGEMENT OF A LOOPER COMPLEX AND A VELVETBEAN CATERPILLAR - GREEN CLOVERWORM COMPLEX ON SOYBEAN, 2002B

Eight insecticides were evaluated to determine rate effects on Soybean looper (SL), Cabbage looper (CL), Green cloverworm (GCW) and Velvetbean caterpillar (VBC) on soybean. Pre-treatment insect counts revealed that larvae of each species were mainly in midto late instars on day 1 prior to application of the insecticides. Looper infestation consisted of 89% SL and 11% CL at the time the insecticides were applied. Because current identification of the larvae in the field is difficult, especially very small larvae, the number of loopers in samples was combined and reported as a looper complex (SL/CL). This same procedure was used to record the GCW and VBC (GCW/VBC) infestations, both species being about equally susceptible to many insecticides. Plots were located at the Mississippi State University Plant Science Research Farm, Mississippi State, MS. Soybeans were planted on May 29, 2002 in 38-inch rows, using the conventional planting system for soybean in the area. Treatment plots were four rows, 35 ft long, arranged in a randomized complete block design with four replications and a 8-ft alley between replications. Insecticide treatments were applied 8 Aug, using a backpack CO2 sprayer, equipped with eight CONEJET T 3X nozzles, 16 inch apart (2 nozzles per row), delivering 10 gpa at 40 psi, with water as a carrier for the insecticide. Soybeans were in the R5 stage. The environmental conditions at application were 68°F , 100% Rh, with sunshine and wind speed of less than 1 mph. Ground cloth samples were taken from the two middle rows of each plot on days 2 and 7 after spray application. Mean number of larvae in each complex was calculated for each date. Data were analyzed using SAS proc ANOVA, and means were separated using Fisher's least significant differences (LSD).

Suitability of transgenic glyphosate-resistant soybeans to green cloverworm (Lepidoptera: Noctuidae).

Host plant suitability to green cloverworm, Hypena scabra (F.), was evaluated on two conventional soybean varieties (Stine 2499-0 and 2972-2) and two RoundUp Ready Soybeans (Stine 2506-4 and 2892-4) with and without exposure to glyphosate. No differences among treatments were detected on developmental time and survivorship. Developmental time from first instar to adult ranged from 24.7 to 25.5 d, and survivorship ranged from 86 to 96%. No sex bias was observed among treatments (proportion of females ranged from 0.41 to 0.50). Morphological differences were observed between sexes; males had a longer and wider thorax, longer wings, and longer body. Females had longer and wider abdomens. Although treatments did not affect size (calculated with principal component analyses), significant differences were observed between males and females. These results suggest that soybean genetic differences (between conventional varieties and analogous transgenic varieties) or plant stress (induced by glyphosate metabolization) do not affect the plant suitability to H. scabra.

Comparison of Insect Sampling Techniques in Snap Bean

ABSTRACT Three sampling techniques including cage-aerosol, sweep net and drop cloth, were compared in their ability to sample insects on snap bean. Few significant differences among the three techniques were detected when used to sample larvae of the corn earworm (CEW), Helicoverpa zea (Boddie), the green cloverworm, Plathypena scabra (Fabricius), or the cabbage looper, Trichoplusia ni (Hubner). The sweep net caught significantly greater numbers of spotted cucumber beetles, Diabrotica undecimpunctata howardi Barber, and tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois). Both are strong fliers and escaped detection with the drop cloth. Although the drop cloth was somewhat faster to use when plants were small, differences in sample time were reduced with larger plants. Throughout the two year study the mean number of CEW larvae per min of sample time was 0.29 with the sweep net and 0.22 with the drop cloth.