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Helicoverpa zea Boddie (Lepidoptera: Noctuidae) is an important pest in many crops in the southern United States. Upon reaching the final larval instar, H. zea quests for a pupation site in the soil. Pupae are vulnerable to mortality since their movement is limited. Soil type and moisture can influence H. zea emergence, but the interaction of these factors has not been demonstrated. We compared sandy and clay soils in greenhouse and laboratory experiments. In the first experiment, we evaluated the preference of larvae to choose either sandy or clay soil for pupation. In a second experiment, we set the sandy soils at different moisture levels and observed prepupae pupation preference in a choice scenario. In a third experiment, we observed prepupae pupation in different moisture levels in a no-choice scenario. In a 4th experiment, we evaluated adult emergence following pupation when we increased moisture or kept it constant. In a final experiment, we evaluated pupation behavior in sandy or clay soils with a webcam and a glass arena. We found that larvae preferred to pupate in sandy soils over clay soils and that pupal success was highest at intermediate moisture levels. In addition, elevated soil moisture levels did not impact the emergence of H. zea between sandy or clay soil. Finally, H. zea did not take longer to burrow in either sandy or clay soil, but the tunnels of the pupal burrow were larger in sandy soil compared to clay soil. Our results clarify H. zea behavior across soil moisture and soil type. [ABSTRACT FROM AUTHOR]

Bollworm poses a significant threat to cotton crops worldwide, including in the Fergana province of Uzbekistan. This study aims to explore innovative approaches to bollworm control and contribute to the global understanding of integrated pest management strategies (IPM). Using an extensive literature review and field observations, the study evaluates the effectiveness of an integrated protection system in reducing reliance on chemical inputs while increasing overall efficiency. The results highlight the multigenerational life cycle of bollworm, its impact on various crops, and the need for artificial biological control methods and targeted insecticide applications. In addition, the study highlights the need to adopt globally accepted IPM practices to ensure sustainable pest management. The findings underscore the importance of collaboration among researchers, farmers, policymakers, and industry representatives in developing and implementing advanced control measures. Through integrated approaches and the incorporation of scientific advances, bollworm infestations can be contained while safeguarding agricultural productivity and minimizing environmental risks. Preprint of this article is available at: https://www.preprints.org/manuscript/202306.1512/v1

Cotton (Gossypium spp) remains a significant source of income in Africa. However, production is limited by high input costs that reduce profit margins. This study aimed to conduct cost analysis on field trials that were conducted to evaluate the effect of chemical insecticides, Chlorpyrifos® 480 EC, Karate® EC, and Bandit® 350 SC compared with biopesticides, Eco-Bb®, Bolldex®, Delfin®, NOMU-PROTEC® and Bb endophyte on the control of cotton insect pests. Delfin® (US$602) was the most expensive pesticide, followed by Bolldex® (US$495.74), while the cheapest pesticide was Chlorpyrifos® (US$28). Other input costs were US$1 396.50 per hectare, with the highest labor cost of US$544. The minimal cost of production from the bollworm trial was recorded from the application of Karate® (US$1 455), while Delfin® (US$1 999) was the highest. Maximum average seed cotton yield was recorded with Bolldex® (6 402 kg ha-1); however, the maximum net profit of up to US$1 445.26 per hectare was registered with Karate® with the highest cost-benefit ratio of 1.8. The average highest seed cotton yield was obtained with Bandit® (6 394 kg ha-1) followed by Bb endophyte (6 297 kg ha-1) in the leafhopper trial. Bandit® and Karate® had the highest net profits of US$ 1,712 and US$ 1,253, respectively. The Bandit® treatment had the highest costbenefit ratio of 2. Generally, biopesticide application was found to be more expensive than chemical insecticides; however, they were all profitable. [ABSTRACT FROM AUTHOR]

Simple Summary: Corn and cotton that produce insecticidal toxins derived from Bacillus thuringiensis (Bt) are widely adopted in the United States to control corn earworm/cotton bollworm, Helicoverpa zea (Boddie), which has resulted in major benefits to growers and the general public. However, resistance evolution in H. zea populations has become a major threat to the sustainability of these crops. Bt sweet corn producing the same toxins as Bt field corn is more attractive to H. zea than field corn and, thus, can function as a sentinel plant to detect early stages of resistance. As part of an existing sentinel monitoring network, this study evaluated changes in H. zea resistance during 2020–2022 by estimating the phenotypic and resistance allele frequencies for toxins in sentinel Bt corn. Transgenic corn and cotton that produce Cry and Vip3Aa toxins derived from Bacillus thuringiensis (Bt) are widely planted in the United States to control lepidopteran pests. The sustainability of these Bt crops is threatened because the corn earworm/bollworm, Helicoverpa zea (Boddie), is evolving a resistance to these toxins. Using Bt sweet corn as a sentinel plant to monitor the evolution of resistance, collaborators established 146 trials in twenty-five states and five Canadian provinces during 2020–2022. The study evaluated overall changes in the phenotypic frequency of resistance (the ratio of larval densities in Bt ears relative to densities in non-Bt ears) in H. zea populations and the range of resistance allele frequencies for Cry1Ab and Vip3Aa. The results revealed a widespread resistance to Cry1Ab, Cry2Ab2, and Cry1A.105 Cry toxins, with higher numbers of larvae surviving in Bt ears than in non-Bt ears at many trial locations. Depending on assumptions about the inheritance of resistance, allele frequencies for Cry1Ab ranged from 0.465 (dominant resistance) to 0.995 (recessive resistance). Although Vip3Aa provided high control efficacy against H. zea, the results show a notable increase in ear damage and a number of surviving older larvae, particularly at southern locations. Assuming recessive resistance, the estimated resistance allele frequencies for Vip3Aa ranged from 0.115 in the Gulf states to 0.032 at more northern locations. These findings indicate that better resistance management practices are urgently needed to sustain efficacy the of corn and cotton that produce Vip3Aa. [ABSTRACT FROM AUTHOR]

Simple Summary: Data collected from studies in 2020 and 2021 determined that concentrations of chlorantriliprole were detected in the leaves up to 28 days after treatment, were detected in petals up to 14 days after treatment, and were not detected in the anthers. Bollworm mortality was determined on leaves, petals, and anthers, with feeding in the field tending to be concentrated on fruiting structures. While bioassay results varied, field results could also be variable in terms of feeding location. Studies were conducted in 2020 and 2021 at the Delta Research and Extension Center in Stoneville, MS, to determine the residual concentrations of chlorantraniliprole in cotton (Gossypium hirsutum, L.) leaves, as well as the concentrations in petals and anthers that developed after the time of application. Foliar applications of chlorantraniliprole were applied at four rates for leaves and two rates for petals and anthers at the second week of bloom. Additional bioassays were conducted to determine mortality of corn earworm (Helicoverpa zea, Boddie) in anthers. For the leaf study, plants were partitioned into three zones consisting of top, middle, and bottom zones. Leaf samples from each zone were analyzed for chemical concentrations at 1, 7, 14, 21, and 28 days after treatment (DAT). Residual concentrations, although variable, persisted through all sampling dates, rates, and zones tested. In this study, chlorantraniliprole remained detectable up to 28 DAT. Results from the cotton flower petal and anther studies detected concentrations of chlorantraniliprole in petals at 4, 7, 10, and 14 DAT, but no concentrations were detected in anthers. Therefore, no mortality of corn earworm was recorded in the anther bioassays. A series of diet-incorporated bioassays were conducted using concentrations previously found in the petal study to determine baseline susceptibilities of corn earworms and predicted mortality. Results from the diet-incorporated bioassays showed similar susceptibility in field and lab colony corn earworms. Concentrations of chlorantraniliprole could provide up to 64% control of corn earworm when feeding occurs on the petals. [ABSTRACT FROM AUTHOR]

The use of insect-resistant transgenic crops producing Bacillus thuringiensis protein Cry toxins (Bt) to control caterpillars is wide-spread. Development of a mechanism to prevent Bt from reaching its target site in the digestive system could result in Bt resistance and resistance to other insecticides active per os. Increased feeding rates by increasing temperature in tobacco budworms, Chloridea virescens, and bollworms, Helicoverpa zea, decreased Bt Cry1Ac susceptibility and mortality. The same was found in C. virescens for Bollgard II plant extract containing Bt Cry1Ac and Cry2Ab2 toxins. Furthermore, H. zea from the same inbred laboratory colony that fed faster independent of temperature manipulation were less susceptible to Bt intoxication. A laboratory derived C. virescens Bt resistant strain demonstrated a higher feeding rate on non-Bt artificial diet than the parental, Bt susceptible strain. A laboratory-reared Bt resistant fall armyworm, Spodoptera frugiperda, strain also fed faster on non-Bt diet compared to Bt susceptible caterpillars of the same species, both originally collected from corn. The studies in toto and the literature reviewed support the hypothesis that increased feeding rate is a behavioral mechanism for reducing caterpillar susceptibility to Bt. Its possible role in resistance needs further study. [ABSTRACT FROM AUTHOR]

BACKGROUND: Crops genetically engineered to make insect‐killing proteins from Bacillus thuringiensis (Bt) have revolutionized management of some pests. However, the benefits of such transgenic crops are reduced when pests evolve resistance to Bt toxins. We evaluated resistance to Bt toxins and Bt cotton plants using laboratory bioassays and complementary field trials focusing on Helicoverpa zea, one of the most economically important pests of cotton and other crops in the United States. RESULTS: The data from 235 laboratory bioassays demonstrate resistance to Cry1Ac, Cry1Fa, and Cry2Ab occurred in most of the 95 strains of H. zea derived from Arkansas, Louisiana, Mississippi, Tennessee, and Texas during 2016 to 2021. Complementary field data show efficacy decreased for Bt cotton producing Cry1Ac + Cry1Fa or Cry1Ac + Cry2Ab, but not Cry1Ac + Cry1Fa + Vip3Aa. Moreover, analysis of data paired by field site and year shows higher survival in bioassays was generally associated with lower efficacy of Bt cotton. CONCLUSIONS: The results confirm and extend previous evidence showing widespread practical resistance of H. zea in the United States to the Cry toxins produced by Bt cotton and corn, but not to Vip3Aa. Despite deployment in combination with Cry toxins in Bt crops, Vip3Aa effectively acts as a single toxin against H. zea larvae that are highly resistant to Cry toxins. Furthermore, Vip3Aa adoption is increasing and previous work provided an early warning of field‐evolved resistance. Thus, rigorous resistance management measures are needed to preserve the efficacy of Vip3Aa against this highly adaptable pest. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Helicoverpa armigera is one of the most destructive insect pests of economically valuable crops in the world. Despite its economic importance, the population genetic structure of this insect remains unexplored in Ethiopia. To investigate the genetic diversity and population structure of H. armigera , we sampled 170 individuals from 15 populations throughout Ethiopia. We sequenced a fragment of the mitochondrial cytochrome b (cyt b) gene and five exon-primed intron-crossing (EPIC) markers. Twenty cyt b haplotypes with low-to-moderate haplotype diversity (mean Hd = 0.537) and high nucleotide diversity (mean Pi = 0.00339) were identified. The most frequently observed and widely distributed cyt b haplotype was designated as Hap_1 (67.058%), which is identical to sequences found across the globe. Tajima's D and Fu's F for the cyt b data were negative, supporting a model of population expansion. Within populations, a mean of 2.493 alleles/locus was recorded across the five EPIC loci, ranging from 1.200 to 3.600 alleles/locus. The highest mean effective number of alleles/population was 2.369 and the lowest was 1.178. The mean observed heterozygosity (H O ) of the five loci (0–0.289; mean 0.104 ± 0.020) was lower than the expected heterozygosity (H E ) (0.095–0.523; mean 0.258 ± 0.028). AMOVA detected significant genetic structure with 61% of the total molecular genetic variation of EPIC genotypes occurring between populations, suggesting a considerable degree of differentiation among populations. STRUCTURE analyses clustered the H. armigera populations into three distinct population groups but very low isolation by distance (R 2 = 0.0132, P < 0.05). [ABSTRACT FROM AUTHOR]

Transgenic corn and cotton that produce Cry and Vip3Aa toxins derived from Bacillus thuringiensis (Bt) are widely planted in the United States to control lepidopteran pests. The sustainability of these Bt crops is threatened because the corn earworm/bollworm, Helicoverpa zea (Boddie), is evolving a resistance to these toxins. Using Bt sweet corn as a sentinel plant to monitor the evolution of resistance, collaborators established 146 trials in twenty-five states and five Canadian provinces during 2020–2022. The study evaluated overall changes in the phenotypic frequency of resistance (the ratio of larval densities in Bt ears relative to densities in non-Bt ears) in H. zea populations and the range of resistance allele frequencies for Cry1Ab and Vip3Aa. The results revealed a widespread resistance to Cry1Ab, Cry2Ab2, and Cry1A.105 Cry toxins, with higher numbers of larvae surviving in Bt ears than in non-Bt ears at many trial locations. Depending on assumptions about the inheritance of resistance, allele frequencies for Cry1Ab ranged from 0.465 (dominant resistance) to 0.995 (recessive resistance). Although Vip3Aa provided high control efficacy against H. zea, the results show a notable increase in ear damage and a number of surviving older larvae, particularly at southern locations. Assuming recessive resistance, the estimated resistance allele frequencies for Vip3Aa ranged from 0.115 in the Gulf states to 0.032 at more northern locations. These findings indicate that better resistance management practices are urgently needed to sustain efficacy the of corn and cotton that produce Vip3Aa.

Studies were conducted in 2020 and 2021 at the Delta Research and Extension Center in Stoneville, MS, to determine the residual concentrations of chlorantraniliprole in cotton (Gossypium hirsutum, L.) leaves, as well as the concentrations in petals and anthers that developed after the time of application. Foliar applications of chlorantraniliprole were applied at four rates for leaves and two rates for petals and anthers at the second week of bloom. Additional bioassays were conducted to determine mortality of corn earworm (Helicoverpa zea, Boddie) in anthers. For the leaf study, plants were partitioned into three zones consisting of top, middle, and bottom zones. Leaf samples from each zone were analyzed for chemical concentrations at 1, 7, 14, 21, and 28 days after treatment (DAT). Residual concentrations, although variable, persisted through all sampling dates, rates, and zones tested. In this study, chlorantraniliprole remained detectable up to 28 DAT. Results from the cotton flower petal and anther studies detected concentrations of chlorantraniliprole in petals at 4, 7, 10, and 14 DAT, but no concentrations were detected in anthers. Therefore, no mortality of corn earworm was recorded in the anther bioassays. A series of diet-incorporated bioassays were conducted using concentrations previously found in the petal study to determine baseline susceptibilities of corn earworms and predicted mortality. Results from the diet-incorporated bioassays showed similar susceptibility in field and lab colony corn earworms. Concentrations of chlorantraniliprole could provide up to 64% control of corn earworm when feeding occurs on the petals.

The bollworm, Helicoverpa armigera, is one of the most important agricultural pests in the world. Diagnosis of this species morphologically is difficult from the similar species H. assulta, H. punctigera and H. zea as the adults are identified based on genitalia morphology and larval identification is limited due to shared morphological characters. To provide an accurate diagnosis of New Zealand border interceptions, we have developed a real‐time PCR assay to identify H. armigera from commonly occurring exotic Helicoverpa species, H. assulta and H. zea. Preliminary studies, using the already available real‐time ITS2 primer–probe detecting H. armigera and H. zea tested on samples obtained from NZ border interceptions and from overseas showed cross reactions with low intensities among H. armigera, H. assulta and H. zea. This prompted PHEL to develop a new real‐time PCR assay to accurately identify H. armigera. The newly designed primer and probe were optimized, and the assay demonstrated its specificity to H. armigera with no false positives observed in the non‐target species tested in this study. The specificity of the assay was tested against 64 samples of Lepidoptera from 14 countries including 48 Helicoverpa samples. The sensitivity of the assay showed it can detect up to 1 copy/µl of the DNA fragment. Therefore, this assay can be used for rapid detection of H. armigera, which is imperative in quarantine application to determine the presence of exotic species regardless of its life stage. [ABSTRACT FROM AUTHOR]

Abstract Background Cotton is the most widespread, profitable non-food crop in the world. Egypt is one of the greatest countries in producing cotton (Gossypium hirsutum L.) in the world. Many pests attacked cotton which reduced the quality and quantity of the cotton yield such as pink bollworm (Pectinophora gossypiella) (Lepidoptera: Gelechiidae) and the spiny bollworm (Earias insulana) (Lepidoptera: Noctuidae). Results The insect infestation increased significantly by delaying planting date. The fewest numbers of pests attacked cotton recorded in the earliest planting date (March 23rd) with highest weight of cotton yield. The results showed that the mean rates of infestation with pink bollworm were (2.11, 3.5, 2.33 individuals/boll) for March 23rd, April 17th and May 6th, respectively, while the mean rates of infestation with bollworm were (1.60, 2.79, 1.67 individuals/boll) for March 23rd, April 17th and May 6th, respectively. Conclusion It was concluded that planting cotton as early as on March 23rd reduces the rate of infestation of E. insulana and P. gossypiella and increases the population of its natural enemies as well. Then, it is resulting a significant increase in the quality and quantity of the yield of cotton.

Widespread field-evolved resistance of bollworm [ Helicoverpa zea (Boddie)] to Cry1 and Cry2 Bt proteins has threatened the utility of Bt cotton for managing bollworm. Consequently, foliar insecticide applications have been widely adopted to provide necessary additional control. Field experiments were conducted across the Mid-South and in Texas to devise economic thresholds for foliar insecticide applications targeting bollworm in cotton. Bt cotton technologies including TwinLink (TL; Cry1Ab+Cry2Ae), TwinLink Plus (TLP; Cry1Ab+Cry2Ae+Vip3Aa), Bollgard II (BG2; Cry1Ac+Cry2Ab), Bollgard 3 (BG3; Cry1Ac+Cry2Ab+Vip3Aa), WideStrike (WS; Cry1Ac+Cry1F), WideStrike 3 (WS3; Cry1Ac+Cry1F+Vip3Aa), and a non-Bt (NBT) variety were evaluated. Gain threshold, economic injury level, and economic thresholds were determined. A 6% fruiting form injury threshold was selected and compared with preventive treatments utilizing chlorantraniliprole. Additionally, the differences in yield from spraying bollworms was compared among Bt cotton technologies. The 6% fruiting form injury threshold resulted in a 25 and 75% reduction in insecticide applications relative to preventive sprays for WS and BG2, respectively. All Bt technologies tested in the current study exhibited a positive increase in yield from insecticide application. The frequency of yield increase from spraying WS was comparable to that of NBT. Significant yield increases due to insecticide application occurred less frequently in triple-gene Bt cotton. However, their frequencies were close to the dual-gene Bt cotton, except for WS. The results of our study suggest that 6% fruiting form injury is a viable threshold, and incorporating a vetted economic threshold into an Integrated Pest Management program targeting bollworm should improve the sustainability of cotton production. [ABSTRACT FROM AUTHOR]

BACKGROUND: Helicoverpa zea (Boddie) damage to Bt cotton and maize has increased as a result of widespread Bt resistance across the USA Cotton Belt. Our objective was to link Bt crop production patterns to cotton damage through a series of spatial and temporal surveys of commercial fields to understand how Bt crop production relates to greater than expected H. zea damage to Bt cotton. To do this, we assembled longitudinal cotton damage data that spanned the Bt adoption period, collected cotton damage data since Bt resistance has been detected, and estimated local population susceptibility using replicated on‐farm studies that included all Bt pyramids marketed in cotton. RESULTS: Significant year effects of H. zea damage frequency in commercial cotton were observed throughout the Bt adoption period, with a recent damage increase after 2012. Landscape‐level Bt crop production intensity over time was positively associated with the risk of H. zea damage in two‐ and three‐toxin pyramided Bt cotton. Helicoverpa zea damage also varied across Bt toxin types in spatially replicated on‐farm studies. CONCLUSIONS: Landscape‐level predictors of H. zea damage in Bt cotton can be used to identify heightened Bt resistance risk areas and serves as a model to understand factors that drive pest resistance evolution to Bt toxins in the southeastern United States. These results provide a framework for more effective insect resistance management strategies to be used in combination with conventional pest management practices that improve Bt trait durability while minimizing the environmental footprint of row crop agriculture. © 2021 Society of Chemical Industry. This article has been contributed to by US Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

The use of insect-resistant transgenic crops producing Bacillus thuringiensis protein Cry toxins (Bt) to control caterpillars is wide-spread. Development of a mechanism to prevent Bt from reaching its target site in the digestive system could result in Bt resistance and resistance to other insecticides active per os. Increased feeding rates by increasing temperature in tobacco budworms, Chloridea virescens, and bollworms, Helicoverpa zea, decreased Bt Cry1Ac susceptibility and mortality. The same was found in C. virescens for Bollgard II plant extract containing Bt Cry1Ac and Cry2Ab2 toxins. Furthermore, H. zea from the same inbred laboratory colony that fed faster independent of temperature manipulation were less susceptible to Bt intoxication. A laboratory derived C. virescens Bt resistant strain demonstrated a higher feeding rate on non-Bt artificial diet than the parental, Bt susceptible strain. A laboratory-reared Bt resistant fall armyworm, Spodoptera frugiperda, strain also fed faster on non-Bt diet compared to Bt susceptible caterpillars of the same species, both originally collected from corn. The studies in toto and the literature reviewed support the hypothesis that increased feeding rate is a behavioral mechanism for reducing caterpillar susceptibility to Bt. Its possible role in resistance needs further study.

Thresholds for Helicoverpa zea (Boddie) in cotton Gossypium hirsutum L. have been understudied since the widespread adoption of Bt cotton in the United States. Our study was possible due to the widespread presence of H. zea populations with Cry-toxin resistance. We initiated progressive spray timing experiments using three Bt cotton brands (Deltapine, Stoneville, and Phytogen) widely planted across the U.S. Cotton Belt expressing pyramided toxins in the Cry1A, Cry2, and Vip3Aa19 families. We timed foliar insecticide treatments based on week of bloom to manipulate H. zea populations in tandem with crop development during 2017 and 2018. We hypothesized that non-Bt cotton, cotton expressing Cry toxins alone, and cotton expressing Cry and Vip3Aa19 toxins would respond differently to H. zea feeding. We calculated economic injury levels to support the development of economic thresholds from significant responses. Pressure from H. zea was high during both years. Squares and bolls damaged by H. zea had the strongest negative yield associations, followed by larval number on squares. There were fewer yield associations with larval number on bolls and with number of H. zea eggs on the plant. Larval population levels were very low on varieties expressing Vip3Aa19. Yield response varied across experiments and varieties, suggesting that it is difficult to pinpoint precise economic injury levels. Nonetheless, our results generally suggest that current economic thresholds for H. zea in cotton are too high. Economic injury levels from comparisons between non-Bt varieties and those expressing only Cry toxins could inform future thresholds once H. zea evolves resistance to Vip3Aa19. [ABSTRACT FROM AUTHOR]

Background: Cotton is the most widespread, profitable non-food crop in the world. Egypt is one of the greatest countries in producing cotton (Gossypium hirsutum L.) in the world. Many pests attacked cotton which reduced the quality and quantity of the cotton yield such as pink bollworm (Pectinophora gossypiella) (Lepidoptera: Gelechiidae) and the spiny bollworm (Earias insulana) (Lepidoptera: Noctuidae). Results: The insect infestation increased significantly by delaying planting date. The fewest numbers of pests attacked cotton recorded in the earliest planting date (March 23rd) with highest weight of cotton yield. The results showed that the mean rates of infestation with pink bollworm were (2.11, 3.5, 2.33 individuals/boll) for March 23rd, April 17th and May 6th, respectively, while the mean rates of infestation with bollworm were (1.60, 2.79, 1.67 individuals/boll) for March 23rd, April 17th and May 6th, respectively. Conclusion: It was concluded that planting cotton as early as on March 23rd reduces the rate of infestation of E. insulana and P. gossypiella and increases the population of its natural enemies as well. Then, it is resulting a significant increase in the quality and quantity of the yield of cotton. [ABSTRACT FROM AUTHOR]

Background: Cotton bollworm (Hubner) (Helicoverpa armigera) (Lepidoptera: Noctuidae) is a major constraint to cotton production and productivity in Ethiopia. Objective: To determine the best spray sequence of various insecticides as a strategy of resistance management of the pest. Materials and Methods: Field experiments were conducted during the 2017 and 2018 main cropping season at Werer Agricultural Research Center. Eight different insecticides (chlorantraniliprole, deltamethrin, chlorfenapyr, lufenuron+profenofos, chlorpyriphos, lambdacyhalothrin, profenofos, and alphacypermethrin) belonging to five major insecticide classes were systematically arranged in six treatments and three spraying sequences along with a control treatment. The experiment was laid out as a Randomized Complete Block Design and replicated four times per treatment. Data were collected on bollworm population, damaged squares, flowers, and bolls at pre and post insecticide application, boll number per plant, and seed cotton yield. Using the modified Abbott's formula, the percent efficacy was computed. Results: Significant differences (P<0.05) were observed among the treatments for post spray larvae count, damaged squares, and boll counts in the 2017 and 2018 cropping seasons. Sequential and rotational application of a cocktail of the insecticides, namely, chlorantraniliprole, chlorfenapyr, profenofos, and chlorfenapyr, chlorantraniliprole, lufenuron+profenofos resulted in the best control with 81.8% and 76.4% of H. armigera larvae controlling efficacy. The lowest average cotton boll number (9.69/plant) and cotton yields (2.24 ton/ha) were obtained from the unsprayed treatment. Conclusion: Applying the insecticides in sequence increased seed cotton yield by 36.2% and 33.9% compared to the yields obtained from the unsprayed plots. The results imply that rotational use of insecticides with different modes of action is the best strategy to control the pest. [ABSTRACT FROM AUTHOR]

Scarcity of water is a severe environmental limit to plant productivity. The plants were grown in a glasshouse as a substrate culture with two watering regimes. The biometric values decrease as a result of a reduced in the water regime. That effect is mostly expressed in the mass of fruits of first quality, where it varies from 27.1% to 69.5%. The most sensitive to the water stress was line C45 and entirely the best tolerance had line C41. The average fruit mass and the fruit mass of the fruits from first quality weren't influenced by reducing the water regime in line No.1928. During the vegetation, an attack of green peach aphid, thrips and cotton bollworm was observed. In full irrigation, there were no differences in thrips attack between pepper genotypes. In plants with reduced water regime, an increase in the density of the thrips was observed as the highest rate of infestation in line C45 was reported. The lowest percentage of damaged cotton bollworm fruits was observed in pepper genotype 1930 in both irrigation modes. [ABSTRACT FROM AUTHOR]

Helicoverpa armigera (Hübner) is the most significant insect pest of chickpea in Ethiopia. Sole reliance on insecticide causes both human and environmental health problems. A common soil bacterium, Bacillus thuringiensis used as a bioinsecticide to control numerous Lepidopteran larvae. Therefore, indigenous isolates were collected, screened, tested for pathogenicity against H. armigera with a reference Bacillus. var. thuringiensis. From 121 soil samples collected, 23 Bacillus species were isolated and purified. Bt index ranged from 0.33 to 1.00 and the mean was 0.73 average Bt index. Absorbance values ranged from 0.46 to 0.98. Screening biotoxicity assay was conducted at the rate of 1 mL against 3rd instar larvae of H. armigera. Experiments were replicated three times; ten larvae were used per replicate and reputed thrice. Ten indigenous Bt isolates were screened based on larval mortality which ranged between 27.78% and 75.83% and LT 50 values of 45.71–143.9 h. The highest mortality of 75.83% and LT 50 of 45.71 h was recorded from reference Bt followed by indigenous Bt isolate KDL with mortality percentage of 69.16% and LT 50 of 48.49 h. Statistically no significant difference was observed among the tested bacterial isolates. Biotoxicity assay was conducted at five concentrations ranging from 0.25 to 2 mL. The LD 50 and LD 90 values were 0.84–1.24 mL and 1.54–1.98 mL, respectively. The lowest LD 50, 90 of 0.84 mL and 1.54 mL were recorded from KDL Bt isolate compared to reference Bt whose LD 50 and LD 90 were 0.84 mL and 1.66 mL. Results of Bt growth under varied values of temperature ranged from 15oC to 40 °C. All the Bt isolates showed growth at all the values of the tested temperatures with steady growth from 15 °C to 20 °C and uniform growth observed from 20 °C to 30 °C. After 35 °C, the growth of all the Bt isolates declined indicating that 30 °C–35 °C is the optimum growth temperature range. Protein content ranged from 0.43 to 0.97 (mg/mL). However, protein content and larval mortality was not linearly correlated. It was concluded that all the tested indigenous Bacillus isolates were virulent enough and identified as a promising candidate bioinsecticide against H. armigera. Hence, recommended for further intensive evaluations under greenhouse and field trails. • Indigenous Bacillus thuringiensis isolates against chickpea pod borer. • Helicoverpa armigera damage on chickpea in Ethiopia. • Bacillus thuringiensis to control H. armigera in Ethiopia. • Chickpea pod borer management in Ethiopia. • Indigenous Bacillus thuringiensis isolates from Ethiopia. [ABSTRACT FROM AUTHOR]

The direct management of insect pests using pheromones for mating disruption, or “attract and kill” approaches, can provide excellent suppression of key lepidopteran pests in agriculture. Important successes to date include codling moth in pome fruit, oriental fruit moth in peaches and nectarines, tomato pinworm in vegetables, pink bollworm in cotton and omnivorous leafroller in vineyards. Large-scale implementation projects have yielded significant reductions in pesticide use while maintaining acceptably low crop-damage levels. Because of some difficulties with high populations of pests, these programs should not be viewed as stand-alone strategies but rather as one tactic within a suite of integrated pest management options.

Helicoverpa zea Boddie is a common economic pest of cotton (Gossypium hirsutum L.), including transgenic cotton varieties that express Bacillus thuringiensis (Bt). Helicoverpa zea oviposition is similar in Bt and non-Bt cotton, but behavior of H. zea larvae can be different in the presence of Bt, with neonates moving away from terminals faster in single-toxin Bt than non-Bt cotton or avoiding Bt-treated diet in the lab. We quantified H. zea oviposition and larval distribution on structures within cotton plants in small plot experiments of Cry1Ac + Cry1F cotton for 2 yr under different irrigation and nitrogen treatments. More eggs were oviposited on plants receiving nitrogen application during 2016 and on leaves in the top section of irrigated plants during 2017, but other treatment effects on eggs or larvae were minimal. Helicoverpa zea eggs were most common on leaves in the top third of plants at position zero and middle section of cotton plants throughout the season, but some oviposition occurred on fruiting structures as well. First and second instars were more common on squares in the top section of plants during 2016 and bolls in the middle and lower sections during 2017 due to oviposition lower in the canopy during 2017. During both years, third through fifth instars were more common on bolls in the middle and lower section of plants closer to the main stem. These findings have resistance management implications as extended larval feeding on bolls could optimize nutrition, decrease Bt susceptibility, and potentially influence behavioral resistance. [ABSTRACT FROM AUTHOR]

In some Bt cotton (Gossypium hirsutum L.) varieties, bollworm (Helicoverpa zea Boddie) larval behavior differs from non-Bt varieties. Laboratory assays indicate bollworm larvae can detect Bt proteins, which may cause behavioral differences. Plant stress from factors including fertility and water availability causes changes in plant physiology and Bt expression. Our objective was to determine whether nitrogen and irrigation influenced bollworm behavior in Bt cotton by recording the vertical distribution of eggs and larvae over time. We conducted small plot experiments with Cry1Ac + Cry1F cotton in 2016 and 2017 with three nitrogen rates, along with irrigated and nonirrigated treatments during 2017. Bollworm locations were determined by in-field examination of 10–20 cotton plants per plot over 6–8 wk. The location of each egg and larva was recorded by node, with instar estimation of each larva. Oviposition was higher in in plots receiving nitrogen; first and second instars were also more common in plots receiving nitrogen or irrigation, whereas older instars had similar numbers among treatments. Oviposition was more evenly distributed throughout the canopy earlier in the sampling period than during later weeks, with more eggs in the top third of the canopy in only three of 14-wk. Early instars were also evenly distributed throughout the canopy. Later, instars moved to the middle portions of the canopy, away from bottom nodes, and did not move toward the terminal. Understanding bollworm behavior can inform both crop scouting and resistance management decisions. [ABSTRACT FROM AUTHOR]

Level of Bt gene expression plays a vital role for better management of cotton bollworm. So the selection of cotton varieties having maximum gene expression at the period of bollworm attack ultimately manage pest better and yield more than the varieties failed to control bollworm attack. Thirty six cross combinations developed from six non-Bt females and six males containing Bt gene (Cry1Ac) were crossed in 6 × 6 North Carolina Design II fashion, were planted during the study period. All the crosses were evaluated to detect the Bt gene by immunostrip assay that exposed the presence of gene Cry1Ac in all crosses. Through quantitative ELISA, Bt gene expression was quantified. Gene expression of Cry1Ac at 30 days after planting in all thirty six cross combinations varied from 1.003 to 2.814µg/g. The top ten cross combinations having maximum gene expression (2.814 to 1.170 µg/g) were selected for further bioassay studies, the mortality% of Earias spp in leaves at 60, 90 and 120 days after planting were also recorded. At 60 days after planting (DAP) mortality was recorded 80% while at 120 DAP mortality percentage dropped to unacceptable level and ranged between 33 to 28%. However some combinations proved effective at 120 DAP as well. Our studies proved that selection of combinations can improve pest management and ultimately enhance yield for the betterment of the farmers and for the country as a whole. [ABSTRACT FROM AUTHOR]

Anthocyanins are a class of pigments ubiquitously distributed in plants and play roles in adoption to several stresses. The red plant gene (R1) promotes light-induced anthocyanin accumulation and red/purple pigmentation in cotton. Using 11 markers developed via genome resequencing, the R1 gene was located in an interval of approximately 136 kb containing three annotated genes. Among them, a PAP1 homolog, GhPAP1D (Gohir.D07G082100) displayed differential transcript level in the red- and green-plant leaves. GhPAP1D encoded a R2R3-MYB transcription factor and its over-expression resulted in increased anthocyanin accumulation in transgenic tobaccos and cottons. Dual luciferase assay indicated that GhPAP1D activated the promoters of several cotton anthocyanin structural genes in tobacco leaves. Importantly, we found that the GhPAP1D-overexpressing cotton leaves had increased resistance to both bollworm and spite mite. Our data demonstrated that GhPAP1D was the controlling gene of the red plant phenotype in cotton, and as the major anthocyanin regulator, this gene was potential to create transgenic cottons with resistance to a broad spectrum of herbivores. [ABSTRACT FROM AUTHOR]

BACKGROUND Field‐evolved resistance of Helicoverpa zea to Bacillus thuringiensis (Bt) toxin Cry1Ac was first reported more than a decade ago, yet the underlying mechanisms remain elusive. Towards understanding the mechanisms of resistance to Cry1Ac, we analyzed a susceptible (LAB‐S) and two resistant (GA and GA‐R) strains of H. zea. The GA strain was derived from Georgia and exposed to Bt toxins only in the field. The GA‐R strain was derived from the GA strain and selected for increased resistance to Cry1Ac in the laboratory. RESULTS: Resistance to MVPII, a liquid formulation containing a hybrid protoxin similar to Cry1Ac, was 110‐fold for GA‐R and 7.8‐fold for GA relative to LAB‐S. In midgut brush border membrane vesicles, activity of alkaline phosphatase and aminopeptidase N did not vary significantly among strains. The activity of total proteases, trypsin‐like proteases and chymotrypsin‐like proteases was significantly lower for GA‐R and GA than LAB‐S, but did not differ between GA‐R and GA. When H. zea midgut cells were exposed to Cry1Ac protoxin that had been digested with midgut extracts, toxicity was significantly lower for extracts from GA‐R and GA relative to extracts from LAB‐S, but did not differ between GA‐R and GA. Transcriptional analysis showed that none of the five protease genes examined was associated with the decline in Cry1Ac activation in GA‐R and GA relative to LAB‐S. CONCLUSION: The results suggest that decreased Cry1Ac activation is a contributing field‐selected mechanism of resistance that helps explain the reduced susceptibility of the GA‐R and GA strains. Relative to the LAB‐S strain, the two Cry1Ac‐resistant strains had lower total protease, trypsin and chymotrypsin activities, a lower Cry1Ac activation rate, and Cry1Ac protoxin incubated with their midgut extracts was less toxic to H. zea midgut cells. © 2018 Society of Chemical Industry Two Cry1Ac‐resistant strains had lower activities of total protease, trypsin, chymotrypsin, Cry1Ac activation rate and Cry1Ac protoxin incubated with their midgut extracts were less toxic to H. zea midgut cells. [ABSTRACT FROM AUTHOR]

Several different agricultural insect pests have developed field resistance to Bt (Bacillus thuringiensis) proteins (ex. Cry1Ac, Cry1F, etc.) expressed in crops, including corn and cotton. In the bollworm, Helicoverpa zea, resistance levels are increasing; recent reports in 2019 show up to 1000-fold levels of resistance to Cry1Ac, a major insecticidal protein in Bt-crops. A common method to analyze global differences in gene expression is RNA-seq. This technique was used to measure differences in global gene expression between a Bt-susceptible and Bt-resistant strain of the bollworm, where the differences in susceptibility to Cry1Ac insecticidal proteins were 100-fold. We found expected gene expression differences based on our current understanding of the Bt mode of action, including increased expression of proteases (trypsins and serine proteases) and reduced expression of Bt-interacting receptors (aminopeptidases and cadherins) in resistant bollworms. We also found additional expression differences for transcripts that were not previously investigated, i.e., transcripts from three immune pathways-Jak/STAT, Toll, and IMD. Immune pathway receptors (ex. PGRPs) and the IMD pathway demonstrated the highest differences in expression. Our analysis suggested that multiple mechanisms are involved in the development of Bt-resistance, including potentially unrecognized pathways.

Migrant populations of Helicoverpa zea (Boddie) captured during 2002, 2005, 2016, and 2018 from Landisville and Rock Springs in Pennsylvania, USA were genotyped using 85 single nucleotide polymorphism (SNP) markers. Samples (n = 702) genotyped were divided into 16 putative populations based on collection time and site. Fixation indices (F-statistics), analysis of molecular variance, and discriminant analysis of principal components were used to examine within and among population genetic variation. The observed and expected heterozygosity in putative populations ranged from 0.317–0.418 and 0.320–0.359, respectively. Broad range of FST (0.0–0.2742) and FIS (0.0–0.2330) values indicated different genotype frequencies between and within the populations, respectively. High genetic diversity within and low genetic differentiation between populations was found in 2002 and 2005. Interestingly, high genetic differentiation between populations from two collection sites observed in 2018 populations was not evident in within-site comparisons of putative populations collected on different dates during the season. The shift of H. zea population genetic makeup in 2018 may be influenced by multiple biotic and abiotic factors including tropical storms. Continued assessment of these peripheral populations of H. zea will be needed to assess the impacts of genetic changes on pest control and resistance management tactics.

Growers of cotton and soybean in Southeast Missouri have expressed deep concern over increases in lepidopteran damage the past 2 years. Efforts to control fall armyworm, bollworm, Southwestern corn borer, and black cutworm with Bt varieties of corn or cotton and foliar insecticides generally meet with limited success. Therefore, we sought a more effective means to monitor and manage these moth populations in cotton, soybean, corn, and grain sorghum by use of pheromone traps and verification of degree-day models. Green plastic funnel traps baited with their respective lures were dispensed and monitored weekly (1 May – 1 Oct 2015, 2016) in 8 randomly selected soybean and cotton fields. Degree-days began at biofix, and a single sine method with lower and upper thresholds were used for the model. Temperature data were obtained from National Oceanic and Atmospheric Administration (NOAA). Each moth peak was assigned accumulative number of degree-days. Accumulated degree-day sums for peak flight of each moth species were estimated by averaging accumulated degree-days between counties for peaks 1–5. For direct comparison, interpretation, and incorporation into a predictive model, differences between the degree-days that flight actually occurred and predictions from models were evaluated with analysis of variance. Factors in the model were county, flight/model, peak, and degree-days. No significant differences in degree-days were found between the peak-flight in degree-days, and the degree-days of its model for the respective moth species, regardless of county. These models are a good fit for predicting catches of moths in monitoring traps and management decisions for Southeast Missouri. [ABSTRACT FROM AUTHOR]

Wolf spiders (Araneae: Lycosidae) are abundant ground predators in cotton fields that can provide important pest management services. These spiders can kill and consume larvae of the cotton bollworm Helicoverpa spp. (Lepidoptera: Noctuidae) that survive foraging on Bt cotton and descend from the plant to pupate in the soil. To determine predation frequency by wolf spiders in a Bt cotton field, we indirectly assessed predation using Helicoverpa spp. larvae marked with rabbit immunoglobulin G (IgG; “immunomarking”), and carried out capture-mark-recapture surveys to assess the likelihood of recapturing spiders. A laboratory feeding study with IgG-marked larva demonstrated that IgG is readily detected in spiders for up to 72 h after feeding. Following the release of IgG-marked larvae in a cotton field edge, 2.1% of spiders collected tested positive for the presence of IgG, providing indirect evidence of predation. A capture-mark-recapture survey revealed that spiders had opportunity to encounter IgG-marked larvae released along field edges, but only 6.7% of the spiders were recaptured, likely reflecting high spider mobility. In field feeding arenas, all three commonly encountered wolf spider species ( Tasmanicosa leuckartii, Hogna crispipes, Hogna kuyani ) ate Helicoverpa spp. larvae. These studies suggest that the low likelihood of spider recapture, and not prey rejection, is the most likely explanation for the low proportion of field-collected spiders testing positive for IgG marked prey remains, and that the frequency of IgG detection in spiders likely underestimated the frequency of predation events. We conclude that use of prey immunomarking together with capture-mark-recapture surveys can provide a powerful tool for assessing the effect of a predator on a prey species under field conditions. [ABSTRACT FROM AUTHOR]

Diverse midgut cadherin mutations confer resistance to Cry1A toxins in at least three lepidopteran pests, including the cotton bollworm, Helicoverpa armigera . Most of these cadherin mutations are inherited as recessive alleles and result in changes within the cadherin repeat (CR) regions of the extracellular protein domain. However, the H. armigera r 15 cadherin mutation results in a deletion of 55 amino acid residues within the cytoplasmic domain, and Cry1A resistance is inherited as a non-recessive trait. Here, eight recombinant H. armigera cadherin (HaCad) proteins, including seven variants containing different combinations of CRs and the cytoplasmic domain, were expressed in cultured insect cells using a baculovirus expression system and were analyzed for Cry1Ac binding and toxicity. Cells expressing either the wild-type HaCad or a mutant lacking only the region corresponding to the first nine CRs bound Cry1Ac and were equally susceptible to Cry1Ac. Cells expressing mutant HaCad proteins without the Cry1A toxin binding region (TBR) located in the CR nearest the plasma membrane did not bind Cry1Ac and were not killed by the toxin. Among the mutant proteins, loss of toxicity was observed in all cells producing HaCad variants lacking the amino acids 1422–1440, indicating that this TBR motif is important for both toxin binding and to confer susceptibility to Cry1Ac. Cells expressing the HaCad variant lacking the entire cytoplasmic domain retained Cry1Ac binding, but were significantly less susceptible to Cry1Ac than the cells producing either wild-type HaCad or HaCad lacking the first nine CRs. These results suggest that both the extracellular and the cytoplasmic domains of HaCad participate in Cry1Ac intoxication. [ABSTRACT FROM AUTHOR]