Jack S. Bacheler

Confirmed Distribution and Occurrence of Megacopta cribraria (F.) (Hemiptera: Heteroptera: Plataspidae) in the Southeastern United States

Abstract Megacopta cribraria (F) (Hemiptera: Heteroptera: Plataspidae) was first discovered in North America in 9 counties in northeastern Georgia (USA) in October 2009. By the end of 2012, surveys conducted in Georgia and neighboring states confirmed that the insect had spread into 383 additional counties in the southeastern U.S., including the states of Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, Tennessee and Virginia. It was reported from 33 species of plants representing 15 taxonomic families in these surveys, with 17 of those from the family Fabaceae (legumes). Kudzu (Pueraria montana Lour. [Merr.] variety lobata [Willd.] Maesen & S. Almeida) was the most frequently reported host. All life stages of the insect were observed only on kudzu and soybean (Glycine max [L.] Merrill) which, to date, are the only confirmed reproductive host plants of M. cribraria in its expanded North American range.

Species Diagnosis and Bacillus thuringiensis Resistance Monitoring of Heliothis virescens and Helicoverpa zea (Lepidoptera: Noctuidae) Field Strains from the Southern United States Using Feeding Disruption Bioassays

Abstract Validation of a feeding disruption bioassay for the detection of resistance to Bacillus thuringiensis toxin and species identification is reported using field strains of Heliothis virescens and Helicoverpa zea collected from the southern United States in 1998. Feeding disruption is measured by a lack of fecal production from larvae exposed to a diagnostic concentration of CryIAc in a blue indicator diet. The bioassay provided rapid (24 h) diagnosis of the species composition of larvae tested and also monitored for the presence of resistance in H. virescens. An additional diagnostic concentration was established for monitoring resistance in H. zea. A probit model was used to compare the fecal production responses of insect strains over a range of CryIAc doses. Probability calculations, derived from our assay results, are also presented to aid in the interpretation of future results from field trials. Integration of the feeding disruption bioassay into integrated pest management programs is discussed.

Efficacy of Transgenic Cotton Expressing Cry1Ac and Cry1F Insecticidal Protein Against Heliothines (Lepidoptera: Noctuidae)

Abstract Cotton, Gossypium hirsutum L, plants expressing Cry1Ac and Cry1F (Phytogen 440W) insecticidal crystal proteins of Bacillus thuringiensis (Bt) Berliner, were evaluated against natural populations of tobacco budworm, Heliothis virescens (F.), and bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), across 13 southern U.S. locations that sustained low, moderate, and high infestations. The intrinsic activity of Phytogen 440W was compared with nontreated non-Bt cotton (PSC355) and with management strategies in which supplemental insecticides targeting heliothines were applied to Phytogen 440W and to PSC355 cotton. Infestations were composed primarily of bollworm, which is the least sensitive of the heliothine complex to Cry toxins. Therefore, damage recorded in these studies was primarily due to bollworm. Greater than 75% of all test sites sustained heliothine infestations categorized as moderate to high (10.6–64.0% peak damaged bolls in nontreated PSC355). Phytogen 440W, alone or managed with supplemental insecticide applications, reduced heliothine-damaged plant terminals, squares (flower buds), flowers, and bolls equal to or better (1.0–79.0-fold) than managing a non-Bt cotton variety with foliar insecticides across all infestation environments. Rarely (frequency of ≤11% averaged across structures), sprayed Phytogen 440W reduced damaged structures compared with nontreated Phytogen 440W. Protection against heliothine-induced plant damage was similar across the three levels of infestation for each viable management strategy, with exception to damaged squares for nontreated Phytogen 440W. In situations of moderate to high heliothine infestations, cotton plants expressing Cry1Ac and Cry1F may sustain higher levels of damage compared with that same variety in low infestations. No significant difference in yield was observed among heliothine management strategies within each infestation level, indicating cotton plants may compensate for those levels of plant damage. These findings indicate Phytogen 440W containing Cry1Ac and Cry1F provided consistent control of heliothines across a range of environments and infestation levels.

Efficacy and Value of Prophylactic vs. Integrated Pest Management Approaches for Management of Cereal Leaf Beetle (Coleoptera: Chrysomelidae) in Wheat and Ramifications for Adoption by Growers

ABSTRACT Cereal leaf beetle, Oulema melanopus L., can be effectively managed in southeastern U.S. wheat, Triticum aestivum L., with scouting and a single insecticide treatment, applied at the recommended economic threshold. However, many growers eschew this approach for a prophylactic treatment, often tank mixed with a nitrogen application before wheat growth stage 30. The efficacy of a prophylactic and an integrated pest management (IPM) approach was compared for 2 yr using small plot studies in North Carolina and regional surveys across North Carolina and Virginia. Economic analyses were performed, comparing the total cost of management of each approach using the regional survey data. From a cost perspective, the prophylactic approach was riskier, because when cereal leaf beetle densities were high, economic loss was also high. However, fields under the prophylactic approach did not exceed threshold as often as fields using IPM. Total cost of prophylactic management was also

Fidelity of External Boll Feeding Lesions to Internal Damage for Assessing Stink Bug Damage in Cotton

20.72 less per hectare, giving this approach an economic advantage over IPM. The majority of fields under the IPM approach did not exceed the economic threshold. Hence, from an economic perspective, both the prophylactic and IPM approaches have advantages and disadvantages. This helps explains the partial, rather than complete, adoption of IPM by southeastern U.S. wheat growers. Cereal leaf beetle was spatially aggregated across the region in 2010, but not in 2011. As a result, from an economic standpoint, prophylaxis or IPM may have a better fit in localized areas of the region than others. Finally, because IPM adoption is favored when it has a strong economic advantage over alternative management approaches, more emphasis should be placed on research to reduce costs within the IPM approach.

Biology, Pest Status, Microbiome and Control of Kudzu Bug (Hemiptera: Heteroptera: Plataspidae): A New Invasive Pest in the U.S.

ABSTRACT Previous research showed that the most precise estimates of stink bug damage in developing cotton bolls are obtained by collecting soft quarter-sized bolls and dissecting them for signs of internal feeding damage, such as internal boll wall warts and/or stained lint. However, this method requires considerable time and effort; therefore, scouts and growers are unwilling to invest adequate resources to make sound pest management decisions. Here, the authors evaluated enumeration of external feeding lesions on groups of 10, 15, 20, or 25 bolls per sample as an alternative sampling procedure. Results relate the similarity of external boll feeding lesions to internal damage as a function of boll sample size and external lesion tally. Inverse prediction confidence intervals (CIs) were also calculated to predict internal boll damage on a new sample based only on external feeding lesions. Results show that linear regression model fit increased when examining at least 20 bolls per sample, and only one external lesion per boll provided as good of model fit as using a minimum of two, three, or four lesions per boll. Inverse prediction CIs suggested that more than one sample (20 bolls per sample) will be required to make external lesions an acceptable method for making reasonably accurate management decisions. F-test lack of fit and significant regression models suggest that examination of external lesions is a promising a method for estimating stink bug damage in cotton.

Analysis of Microscopic Injuries Caused by Southern Green Stink Bug (Hemiptera: Pentatomidae) Feeding on Cotton Bolls

Soybean is an important food crop, and insect integrated pest management (IPM) is critical to the sustainability of this production system. In recent years, the introduction into the United States of the kudzu bug currently identified as Megacopta cribraria (F.), poses a threat to soybean production. The kudzu bug was first discovered in the state of Georgia, U.S. in 2009 and since then has spread to most of the southeastern states. Because it was not found in the North American subcontinent before this time, much of our knowledge of this insect comes from research done in its native habitat. However, since the U.S. introduction, studies have been undertaken to improve our understanding of the kudzu bug basic biology, microbiome, migration patterns, host selection and management in its expanding new range. Researchers are not only looking at developing IPM strategies for the kudzu bug in soybean, but also at its unique relationship with symbiotic bacteria. Adult females deposit bacterial packets with their eggs, and the neonates feed on these packets to acquire the bacteria, Candidatus Ishikawaella capsulata. The kudzu bug should be an informative model to study the co-evolution of insect function and behavior with that of a single bacteria species. We review kudzu bug trapping and survey methods, the development of bioassays for insecticide susceptibility, insecticide efficacy, host preferences, impact of the pest on urban environments, population expansion, and the occurrence of natural enemies. The identity of the kudzu bug in the U.S. is not clear. We propose that the kudzu bug currently accepted as M. cribraria in the U.S. is actually Megacopta punctatissima, with more work needed to confirm this hypothesis.

Relationship between external stink bug (Hemiptera: Pentatomidae) boll-feeding symptoms and internal boll damage with respect to cotton lint gin-out and fiber quality.

Abstract. The southern green stink bug, Nezara viridula (L.), utilizes stylets while feeding to pierce the wall of a boll of cotton, Gossypium hirsutum L., and can inoculate disease-causing pathogens into developing green bolls. Detection of diseased bolls is difficult because the surface of the carpel wall frequently lacks apparent macroscopic evidence of insect feeding regardless of infection; blisters on the interior surface of the carpel wall are commonly masked by darkened necrotic tissue. The objectives of this study were to characterize microscopic evidence of feeding by laboratory-reared southern green stink bugs on greenhouse-grown cotton bolls and to use these findings to aid in detection of feeding evidence by piercing-sucking insects on field-collected bolls from four southeastern states. Microscopic analyses of greenhouse-reared bolls fed upon by southern green stink bug (n = 40) yielded definitive characteristics and imagery of feeding evidence. Salivary flanges on the exterior surface of the boll and blisters at the feeding site on the interior surface of the carpel wall were characteristic of feeding by southern green stink bug. Also, salivary flanges were associated with all external puncture wounds on the boll wall. These characteristics were used as the baseline to detect feeding by feral piercing-sucking pests on field-grown bolls during the 2008 and 2009 production seasons. Injury characteristics from field-grown bolls were comparable to characteristics observed in greenhouse-reared bolls after feeding by southern green stink bug. A few field-collected bolls (5%; n = 160) possessed discolored seeds and exhibited evidence of boll feeding externally but lacked blisters on the interior surface of the carpel wall, thus suggesting an incomplete breach of the interior carpel wall. Callus tissue, colloquially termed a ‘wart,’ on the interior surface of the boll carpel wall is typically associated with feeding by stink bugs but was not detected in bolls grown in a greenhouse and was only sporadically detected in bolls collected from the field. When present, callus tissue was always associated with an external puncture. This is the first study to unequivocally illustrate microscopic characteristics associated with feeding damage by southern green stink bug on cotton bolls. Findings are discussed in relation to evidence of feeding by insects in field-collected bolls of unknown age and history.

Long-Term Empirical and Observational Evidence of Practical Helicoverpa zea Resistance to Cotton With Pyramided Bt Toxins

ABSTRACT Cotton, Gossypium hirsutum L., bolls from 17 field locations in northeastern North Carolina and southeastern Virginia, having 20% or greater internal boll damage, were studied to determine the relationship between external feeding symptoms and internal damage caused by stink bug (Hemiptera: Pentatomidae) feeding. In 2006 and 2007, two cohorts of 100 bolls each were sampled at all field locations. The first cohort was removed as bolls reached approximately quarter size in diameter (2.4 cm). External and internal symptoms of stink bug feeding were assessed and tabulated. Concurrent to when the first cohort was collected, a second cohort of quarter-size-diameter bolls was identified, tagged, examined in situ for external feeding symptoms (sunken lesions), and harvested at the black seed coat stage. Harvested bolls were assessed for internal damage and locks were categorized (undamaged, minor damage, or major damage), dried, and ginned. Lint samples from each damage category were submitted for high volume instrument and advanced fiber information system quality analyses. Significant, moderately strong Pearson correlation coefficients existed between number of external stink bug feeding lesions and internal damage. Pearson correlation of total external lesions with total internal damage was stronger than any correlation among the other single components compared. Predictability plots indicated a rapid increase in relationship strength when relating external stink bug lesions to internal damage as the number of external lesions increased. Approximately 90% predictability of internal damage was achieved with four (2006) or six (2007) external lesions per boll. Gin-turnout and fiber quality decreased with increasing intensity of internal stink bug damage.

Systemic Imidacloprid Affects Intraguild Parasitoids Differently

Abstract Evidence of practical resistance of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) to Bt cotton in the United States is debatable, supported with occasional reports of boll damage in the field. Our objective was to provide both empirical and long-term observational evidence of practical resistance by linking both in-season and end-of-season measurements of H. zea damage to pyramided Bt cotton bolls and to provide Cry1Ac diet-based bioassay data in support of these damage estimates. In-season boll damage from H. zea was highly correlated to end-of-season damaged bolls. Across North Carolina, Bt cotton fields with end-of-season bolls damaged by H. zea increased during 2016 compared to previous years. Elevated damage was coupled with an increase in field sprays targeting H. zea during 2016, but not related to an increase in H. zea abundance. Bioassay data indicated that there was a range of Cry1Ac susceptibility across the southeastern United States. Given the range of susceptibility to Cry1Ac across the southeastern United States, it is probable that resistant populations are common. Since H. zea is resistant to cotton expressing pyramided Cry toxins, the adoption of new cotton varieties expressing Vip3Aa will be rapid. Efforts should be made to delay resistance of H. zea to the Vip3Aa toxin to avoid foliar insecticide use.