Bollworm Populations Research Articles

Pink Bollworm management in cotton: Challenges, innovations, and sustainable solutions

Pink bollworm (Pectinophora gossypiella) poses a significant threat to cotton production worldwide. Despite the initial success of Bt cotton, resistance has emerged, necessitating alternative management strategies. Integrated Pest Management (IPM) approaches, including mating disruption and the sterile insect technique (SIT), offer promising solutions. The SPLAT (Specialized Pheromone and Lure Application Technology) technique utilizes wax-based formulations to disrupt pink bollworm mating behaviour, reducing population growth and damage to cotton crops. Meanwhile, SIT utilizes radiation to induce sterility in pink bollworm populations, reducing reproductive rates and mitigating infestation levels. Embracing these innovative strategies collectively ensures sustainable cotton cultivation, safeguarding farmers' livelihoods and reinforcing resilience against the persistent threat of the pink bollworm. Keywords: Pectinophora gossypiella, Cotton, IPM, SPLAT, STI

Effect of weather parameters on pink bollworm damage and population of predators in Bt cotton in Central India

Effect of weather parameters on pink bollworm damage and population of predators in Bt cotton in Central India

Demonstration and Adoption of Integrated Pest Management Strategies for the Management of Pink Bollworm Pectinophora gossypiella (Saunders) in Cotton

The present study was carried out in the farmers’ fields of Bhadradri Kothagudem, Telangana, India during Kharif (June–December) seasons of 2018, 2019 and 2020 to demonstrate the integrated pest management strategies for the management of pink bollworm and to know its rate of adoption among the farming community. The treatments consisted of technology demonstration and farmers’ practice. During three years of study, the population of pink bollworm has showed increasing trends. More than 10% of the rosette flowers were observed during the crop period starting from 36th SMW and continued up to 48th SMW. The green boll damage caused by PBW ranged between 2.1–19.2 in the demo plot, while the range was 2.2–20.6 in the control. Average population in pheromone traps was 4.48, 5.31 and 5.34 trap-1 during 2018, 2019 and 2020 respectively. Standard weeks 36–38 (3rd September–23rd September) 51–3 (17th December–21st January) were minimum or no activity periods due to low temperature, while standard weeks, 40–44 (1st October–4th November) were high activity periods during these study years. The population of pheromone traps correlated with temperature and rainfall had shown negative and non-significant correlation during 2018 and 2020, while positive and non-significant correlation during 2019. Cotton seed yield in the technology demonstrated plot was higher (1965, 2055 and 2095 kg ha-1) compared to farmers practice (1607, 1708 and 1725 kg ha-1) during 2018, 2019 and 2020 respectively. By adopting the IPM strategies against this pest, farmers’ can avoid the yield losses up to 22.3%. Nearly 65% of the respondents had medium level of adoption on management practices for the control of PBW.

Effect of Novel Insecticides on Sucking Pests and Pink Bollworm in Cotton Plants under Field Conditions

The study investigated that the effectiveness of various novel insecticides for controlling sucking pests and pink bollworm in cotton cultivation over a three-year period. The treatments were evaluated based on their impact on aphids, jassids, thrips, whiteflies and pink bollworm populations. During 2018-19, 2019-20 and 2020-21 years, among the tested novel insecticides, Fipronil + Imidacloprid @ 100g/ha has recorded lowest population of thrips, jassids. Similarly, Fipronil+ Acetamiprid @ 1000 ml/ha has recorded lowest aphid population whereas incidence of pink bollworm was least in Lamdacyhalothrin + Chlorantraniliprole @ 200 ml/ha.

Entomopathogenicity of Ascomycete Fungus Cordyceps militaris on the Cotton Bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)

This study investigated the exposure of the cotton bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) to a novel pathogenic fungal agent historically associated with human medicinal value, a commercial strain of Cordyceps militaris ((L.) Fr.) Vuill. (Hypocreales). A series of comparative studies were conducted to evaluate the efficacy of two different exposure methods using four concentrations (n × 109, n × 108, n × 107, n × 106) of C. militaris, where n × 109 provided a concentration of approximately 420 ± 37 spores per mm2 with 398 ± 28 viable spores. Survival of cotton bollworms of all stages was not affected by C. militaris at any concentration 1 d post-exposure. The greatest reduction in survival and highest sporulation rates were observed primarily on or after 7 d post-exposure for early instars (first and second). Significant declines in the survival of early instars were observed for all concentrations at 7 d, and 95% mortality by 10 d, with the exception of the fifth instars that experienced a less severe reduction in survival (35%) when exposed to any concentrations used in the study. Survival of late instars (third to fifth) ranged from 44% to 68% on day 10, while adult survival was near 99% across the duration of the experiment. The relatively narrow range observed for both the lethal concentration and sporulation of second, third, and fifth instar cotton bollworms exposed to the C. militaris strain may demonstrate potential field application for control of larval populations of cotton bollworms.

Cross Resistance Patterns Associated with Spinosad Resistant Helicoverpa armigera (Hubner) in South India

Aim: To study the cross resistance patterns associated with Helicoverpa armigera (Hubner) in south India.
 Study Design: Bioassay.
 Place and Duration of Study: The experiment was carried out in the Department of Entomology, College of Agriculture, Rajendranagar, Hyderabad,Telangana from February 2010 to May 2011.
 Methodology: Spinosad resistant Helicoverpa armigera population in F1 and F2 subjected to different insecticides to know the cross resistance patterns associated.
 Results: American bollworm population of Mahaboobnagar has developed 0.308 and 0.646 folds and 0.284 and 0.624 folds in Raichur population as compared with the Nagpur baseline population at F1. Mahaboobnagar population displayed a negative cross resistance ratio of 0.677 fold to cypermethrin, 0.806 fold to methomyl, 0.935 fold to indoxacarb and positive cross resistance of 1.039 fold to spinosad, similar trend was followed in Raichur population with a negative cross resistance ratio of 0.918 fold to cypermethrin, 0.543 fold to methomyl, 0.642 fold to indoxacarb and 1.060 fold to spinosad. Further, the Nagpur population exihibited a similar trend with a negative cross resistance ratio of 0.604 fold to cypermethrin, 0.690 fold to methomyl, 0.570 fold to indoxacarb and positive cross resistance ratio of 1.077 fold to spinosad at F3.
 Conclusion: The present study revealed that the continuous application of same insecticide across the generations increases the resistance from F1 to F3. Alternating the new chemistries with old conventional chemicals results in no cross resistance development as it was observed in all three populations studied.

Genetic diversity of cotton Pectinophora gossypiella (Saunders) (Lepidoptera, Gelechiidae) population in inferred from mitochondrial COI sequences

The objective was to identify different haplotypes network of pink bollworm and their distribution in south India using the partial mitochondrial COI sequence of pink bollworm populations. Genetic diversity analysis exhibited the presence of 5 haplotypes in COI gene sequences, and among them, Hap_1 was the most common and present in 17 populations. Distributions of pairwise differences obtained with partial COI data from the overall populations were unimodal, suggesting population expansion. A significant neutrality test based on Tajima’s D, Fu and Li’s D and F test presented a haplotype network with multiple haplotypes. The acceptance of the neutrality test with significant positive values validated the theory of demographic expansion in cotton pink bollworm populations with respect to COI. The pink bollworm has a population genetic diversity among the investigated populations collected from south India.

Evaluation and comparison of different refugia-in-bag (RIB) patterns against boll worm complex with special reference to pink boll worm in Bt cotton

Field study on evaluation and comparison of different refugia-in-bag patterns (RIB) against bollworm complex with special reference to pink bollworm was conducted at RARS, Nandyal during 2021 and 2022. Among different RIB patterns evaluated pooled results of two years indicated no significant difference in green boll and locule damage due to pink bollworm among different refugia patterns. Highest yield of 1002 kg/ha was recorded in 20% structured refugia which is statistically at par with all other refugia patterns except in 100% non Bt which recorded lowest yield of 762 kg/ha. Based on foregoing results it clearly states that refugia is longer effective against pink bollworm population which had already developed resistance therefore further development of resistance can be managed in pink bollworm and can be effectively utilized for other bollworm in slowing down the building up of resistance in Bt cotton.

Segregation of Cry Genes in the Seeds Produced by F1 Bollgard® II Cotton Differs between Hybrids: Could This Be Linked to the Observed Field Resistance in the Pink Bollworm?

Indian populations of the Pink Bollworm (PBW) are resistant to Bt (Bacillus thuringiensis) cotton hybrids containing Cry1Ac and Cry2Ab genes. Segregation of these Cry genes in F1 hybrids could subject PBW to sublethal concentrations. Moreover, planting hybrids with varying zygosities of Cry genes could produce diverse segregation patterns and expose PBW populations to highly variable toxin concentrations. This could potentially promote the rate of resistance development. Therefore, we studied the segregation patterns of Cry genes in different commercial Bt hybrids cultivated in India. Results showed that two hybrids segregated according to the Mendelian mono-hybrid ratio, three segregated according to the Mendelian di-hybrid ratio, and one showed a mixed segregation pattern. The assortment of seeds containing Cry genes varied between bolls of the same hybrid. In India, different Bt cotton hybrids are cultivated in small patches next to each other, exposing PBW populations to sublethal doses and wide variations in the occurrence of Cry genes. It is necessary to avoid segregation of Cry genes in the seeds produced by F1 hybrids. This study recommends using Bt parents homozygous for Cry genes in commercial Bt cotton hybrid development. This breeding strategy could be effective for similar transgenic crop hybrids as well.

Bio-efficacy of various insecticides on larval population of pink bollworm infesting transgenic cotton

Bio-efficacy of various insecticides on larval population of pink bollworm infesting transgenic cotton

Cyclosporin A acts as a novel insecticide against Cry1Ac-susceptible and -resistant Helicoverpa armigera

Cotton bollworm (Helicoverpa armigera) is an economically important pest, which is difficult to manage due to its biological and ecological traits, and resistance to most insecticides. Alternative compounds for the sustainable management of H. armigera are needed. As a fungal metabolite, Cyclosporin A (CsA) has not been applied in agriculture pests. Here, CsA was evaluated as a propective insecticide for H. armigera. The results showed that CsA displayed high insecticidal activity against both Cry1Ac-susceptible and -resistant populations of H. armigera. Moreover, lower concentrations of CsA had clear effects, including significantly reduced pupal weight, pupation rate, emergence rate, ovary size, female fecundity and egg hatchability. Further study confirmed that CsA suppressed calcineurin activity and the subsequent expression of endogenous antimicrobial peptide genes (APMs), leading to impaired immunity, ultimately resulting in delayed development and increased mortality. Thus, CsA treatment could control the cotton bollworm population and even showed efficacy against those with Bt resistance. In addition, the morphological changes observed in insects fed CsA with lower concentrations provide insight into insect immunity, regulation of growth and development, regulation of body color, ovary development and sexual selection under external pressure. Overall, our study provides information on biological control potential of Cry1Ac-susceptible and -resistant populations of H. armigera to develop novel bioinsecticides.

Heterologous expression of cry3Bb1 and cry3 genes for enhanced resistance against insect pests in cotton

Transgenic technology played a crucial role in developing insect-resistant plants resulting in the reduced application of pesticides. This article reports the expression of two cry proteins (Cry3Bb1 and Cry3) in cotton for enhanced resistance against chewing insect pests. The aforementioned genes were synthetically developed and were cloned under appropriate regulatory sequences followed by transformation into Eagle-2 genotype (Gossypium hirsutum) of cotton through shoot apex-cut Agro-infiltration. The transgene integration was validated by polymerase chain reaction using primers flanking the aforementioned cry genes. Transgene expression was assessed by qRT-PCR using GADPH as a reference gene. The relative fold expression analyses revealed the highest expression of the transgene(s) in M1 plants, which is a 4.5-fold expression (Cry3 + Cry3Bb1) followed by M3 (fold expression, 3.0) (Cry3Bb1) and M2 (fold expression, 2.5) (Cry3) transformants of cotton. The confirmed transgenic plants were exposed to insect pests, pink bollworm (Pectinophora gossypiella), and army bollworm (Helicoverpa armigera). Bioassay results revealed that 60% mortality was observed against pink bollworm, and 75% mortality was observed against army bollworm in transgenic plants containing both Cry3Bb1 and Cry3 genes (M1 transgenic plants). In M2 transgenic plants containing only the Cry3Bb1 gene, the mortality was observed to be 40% in the pink bollworm population, whereas 45% mortality was observed in the army bollworm population. In the case of M3 transgenic plants containing single gene-Cry3, the mortality was 20% in the pink bollworm population, whereas 30% mortality was observed in the army bollworm population. Almost no mortality was observed in non-transgenic Eagle-2 control plants. Hence, the developed cotton transformants have improved resistance against chewing insect pests.

Extension Interventions for Enlightening Tribal Farmers for Enhancing Cotton Production in Nalgonda District, Telangana

Cluster Frontline Demonstrations using IPM technologies were conducted on farmer fields’ during two consecutive years of both kharif (June-November 2017 and 2018) by Krishi Vigyan Kendra, Kampasagar, Telangana State, India. The results revealed that, 16.9% increased cotton yield was observed in demonstration plot (2234.0 kg ha-1) against farmers practice (1910.5 kg ha-1). The average gross returns, net returns, and benefit-cost ratios were higher in the demonstration plot as compared to the farmers’ practice. The average cost reduction was (Rs. 41402.0 ha-1) in the demonstration plot when compared to farmers’ practice (Rs. 46190.0 ha-1). Incidence of sucking pests and pink bollworm was low in demonstrations plots and adoption of IPM practices i.e. stem application in cotton at 30 and 45 days after sowing with Monocrotophos and water (1:4) ratio and 60 days after sowing with Imidacloprid and water (1:20) ratio minimize the sucking pests. Further erection of pheromone traps @ 10 ha-1 at 45 DAS to monitor pink bollworm population and spraying of need-based plant protection chemicals i.e. Azadirachtin 0.15% EC @ 2.5 l ha-1 and Thiodicarb 75% WP @ 1.5 g l-1 at early stages and Emamectin benzoate 5% SG @ 0.5 g l-1 at later stages effectively controlled pink bollworm. The average extension gap, technology gap, and technology index were 323.25 kg ha-1, 266.25 kg ha-1 and 10.65%, respectively. Hence, adoption of IPM technologies play a major role for controlling the pest complex and need arises to adopt and popularize this technology in the cotton farming to mitigate the wider extension gap between improved and farmers’ practices.

English

American bollworm (Helicoverpa armigera) is poly-phagous pest which infects major fiber, pulses and vegetable crops, e.g., cotton, soybean, chickpea, brinjal, tomato, peas, beans, okra, and chili in Pakistan. Farmers use the different dosage of insecticides to control American bollworm on various crops that might be due to the existence of genetically diverse American bollworm population. So, it is essential to explore and get an understanding of this genetic variation existing among American bollworm, feeding on different host plants. The current study was conducted to observe the genetic variation existing among seven American bollworm populations by RAPD-PCR system collected from host plant including cotton, pea, green bean, chili, green chili, tomato and okra. Overall, 210-bands were obtained from thirty RAPD primers, out of these, 34-bands were polymorphic, and 176-bands were monomorphic. PIC values ranged from 0.2149 to 0.5014, with a mean of 0.2838. Genetic similarity ranged from 92.38% (produced by cotton and peas) to 99.52% (produced by chili and green beans) and the genetic distance range from 0.48% to 7.92%. A most important result was the clustering of the population occurring on green bean, chili, green chili, tomato and okra in one cluster. In contrast, the population occurring on cotton and pea were designated separate clusters, respectively. These results showed that population occurring on cotton and pea were most dissimilar to other populations indicating that populations are closely related to each other. There might be an interspecific crossing frequency among these populations.

Population genomics provides insights into lineage divergence and local adaptation within the cotton bollworm.

The cotton bollworm Helicoverpa armigera is a cosmopolitan pest and its diverse habitats plausibly contribute to the formation of diverse lineages. Despite the significant threat it poses to economic crops worldwide, its evolutionary history and genetic basis of local adaptation are poorly understood. In this study, we de novo assembled a high-quality chromosome-level reference genome of H. a. armigera (contig N50=7.34Mb), with 99.13% of the HaSCD2 assembly assigned to 31 chromosomes (Z-chromosome + 30 autosomes). We constructed an ultradense variation map across 14 cotton bollworm populations and identified a novel lineage in northwestern China. Historical inference showed that effective population size changes coincided with global temperature fluctuation. We identified nine differentiated genes in the three H. armigera lineages (H. a. armigera, H. a. conferta and the new northwestern Chinese lineage), of which per and clk genes are involved in circadian rhythm. Selective sweep analyses identified a series of Gene Ontology categories related to climate adaptation, feeding behaviour and insecticide tolerance. Our findings reveal fundamental knowledge of the local adaptation of different cotton bollworm lineages and will guide the formulation of cotton bollworm management measures at different scales.

Using pheromones to control the population of cotton bollworm on soybeans in the central zone of the Krasnodar territory

Using pheromones to control the population of cotton bollworm on soybeans in the central zone of the Krasnodar territory

Detoxifying Enzymatic Activity and Insecticide-Resistance Gene Expression in Field Populations of Pink Bollworm (Pectinophora Gossypiella (Saund.))

Detoxifying Enzymatic Activity and Insecticide-Resistance Gene Expression in Field Populations of Pink Bollworm (Pectinophora Gossypiella (Saund.))

EFFECT OF INUNDATIVE RELEASE OF TRICHOGRAMMA CHILONIS AGAINST HELICOVERPA ARMIGERA (HUBNER)(LEPIDOPTERA: NOCTUIDAE) ON YIELD OF PEA CROP

The present study was conducted at ARI Quetta during the year 2018, to know the outcome of egg parasitoid (Trichogrammachilonis) against Helicoverpaarmigera and spotted bollworm complex. The observations were recorded on the weekly basis population of Helicoverpaarmigera and spotted bollworm under control and biological control plots. The reduction percentage and crop yield was also calculated. Spotted bollworm maximum population in control plot was counted in second week (15.82±2.48) and minimum population was observed in sixth week (12.56±1.53b) during ten weeks respectively. Spotted bollworm population in biological plot (Trichogrammachilonis) maximum population was observed (10.90±1.61) during 1 weeks and least population was observed in tenth week (8.12±0.32) in treated plot. Helicoverpaarmigera population in control plot maximum population was counted (16.74±2.23) during 9th week and minimum population was observed (13.54±1.75 b) during 10 weeks duration, respectively. Helicoverpaarmigera population in biological plot (Trichogrammachilonis) maximum population was counted (11.90±1.72a) and minimum population was observed (9.08±0.33d) during 10 weeks of duration, respectively. Statistical analysis indicates that there was no significant variation in spotted bollworms and Helicoverpaarmigera population for control plot in all weeks, but significant variation in population of both lepidopteran complexes in biological control (Trichogrammachilonis) plot in all weeks.
 The data indicates that 61.33% and 66.57% reduction was observed in spotted bollworms and Helicoverpaarmigeraunder biological control (Trichogrammachilonis). It was noted that Trichogrammachilonis is valuable biological agent for Integrated Pest Management program.

Feeding Behavior and Fruiting Form Damage by Bollworm (Lepidoptera: Noctuidae) in Bt Cotton.

Bt technologies have played a major role in the control of bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), in cotton. Variation in expression levels among varieties and plant parts, along with selection pressure on bollworm populations, has led to the development of resistance to some Bt proteins. Trials were conducted to evaluate how cotton varieties expressing different Bt proteins affect bollworm larval behavior and their damage in flowering cotton. Differences in larval recovery were observed among cotton varieties at 3 d with 3-gene Bt cotton having the lowest recovery and non-Bt cotton having the greatest recovery. Loss of bloom tags and abscission of small bolls at the site of infestation affected bollworm larval recovery among varieties. Day after infestation was the main factor that affected bollworm movement across all varieties. Number of total damaged fruiting forms by an individual bollworm larva was different among all varieties. Overall, flower bud (square) and fruit (boll) damage by an individual larva was lower on 3-gene cotton than 2-gene cotton and non-Bt cotton. An individual larva damaged fewer squares on 2-gene cotton than non-Bt cotton, but boll damage from bollworm was similar among 2-gene cotton and non-Bt cotton. The level of square and boll damage in 2-gene cotton has increased compared to previous research further supporting the occurrence of bollworm resistance to Cry proteins. The 3-gene cotton containing the Vip3A gene experienced low levels of damage and survival. These results will be important for improving management recommendations of bollworm in Bt cotton technologies.

CRISPR-mediated mutations in the ABC transporter gene ABCA2 confer pink bollworm resistance to Bt toxin Cry2Ab

Crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) have many benefits and are important globally for managing insect pests. However, the evolution of pest resistance to Bt crops reduces their benefits. Understanding the genetic basis of such resistance is needed to better monitor, manage, and counter pest resistance to Bt crops. Previous work shows that resistance to Bt toxin Cry2Ab is associated with mutations in the gene encoding the ATP-binding cassette protein ABCA2 in lab- and field-selected populations of the pink bollworm (Pectinophora gossypiella), one of the world’s most destructive pests of cotton. Here we used CRISPR/Cas9 gene editing to test the hypothesis that mutations in the pink bollworm gene encoding ABCA2 (PgABCA2) can cause resistance to Cry2Ab. Consistent with this hypothesis, introduction of disruptive mutations in PgABCA2 in a susceptible strain of pink bollworm increased the frequency of resistance to Cry2Ab and facilitated creation of a Cry2Ab-resistant strain. All Cry2Ab-resistant individuals tested in this study had disruptive mutations in PgABCA2. Overall, we found 17 different disruptive mutations in PgABCA2 gDNA and 26 in PgABCA2 cDNA, including novel mutations corresponding precisely to single-guide (sgRNA) sites used for CRISPR/Cas9. Together with previous results, these findings provide the first case of practical resistance to Cry2Ab where evidence identifies a specific gene in which disruptive mutations can cause resistance and are associated with resistance in field-selected populations.