Indian scenario on the occurrence of a dreaded insect pest Pink bollworm, Pectinophora gossypiella on Bt cotton-A review

The pink bollworm, Pectinophora gossypiella, has become a significant production constraint on Bt cotton in India. This problem is unique to India because the pest has developed multi-fold resistance to Cry toxins in many Indian populations but not in other countries. Most Indian populations have developed multifold resistance to Cry 1 Ac and Cry 1Ac + Cry 2 Ab toxins. Year-round cultivation of long-duration Bt cotton hybrids on a large scale has a pronounced impact on the incidence. Also discussed other factors responsible for the occurrence of pink bollworm on Bt cotton in India. Insecticide Resistance Management (IRM) strategies implemented by different cotton-growing countries globally; the USA, India, and China had a significant impact on the interaction of pink bollworm on Bt cotton. Huge selection pressure resulted in resistance to Cry toxins. Time-tested IPM, if implemented on a community basis focusing on pheromones technology and closed season, will help sustain the cotton cultivation in India in the future. Thus, this review aims to congregate exhaustive information on the history, biology, resistance to Bt cotton, and Integrated Management (IPM) options for the Indian scenario, which would help researchers in their future endeavors.

Mutation in the Cadherin Gene Is a Key Factor for Pink Bollworm Resistance to Bt Cotton in China

Transgenic crops producing Bacillus thuringiensis (Bt) toxins are widely planted for insect control, but their efficacy may decrease as insects evolve resistance. Understanding the genetic basis of insect resistance is essential for developing an integrated strategy of resistance management. To understand the genetic basis of resistance in pink bollworm (Pectinophora gossypiella) to Bt cotton in the Yangtze River Valley of China, we conducted an F2 screening for alleles associated with resistance to the Bt (Cry1Ac) protein for the first time. A total of 145 valid single-paired lines were screened, among which seven lines were found to carry resistance alleles. All field parents in those seven lines carried recessive resistance alleles at the cadherin locus, including three known alleles, r1, r13 and r15, and two novel alleles, r19 and r20. The overall frequency of resistance alleles in 145 lines was 0.0241 (95% CI: 0.0106–0.0512). These results demonstrated that resistance was rare and that recessive mutation in the cadherin gene was the primary mechanism of pink bollworm resistance to Bt cotton in the Yangtze River Valley of China, which will provide a scientific basis for implementing targeted resistance management statics of pink bollworm in this region.

Bio-efficacy of Certain Insecticides Sequence on Cotton Sucking Pests and Pink Bollworm

The field trials were conducted for two consecutive years during kharif, 2018 and 2019 seasons in the Regional Agricultural Research Station, Warangal, Telangana, India. The susceptible hybrid RCH-2 was grown during both the years of study. Among the treatments, significant (25.4%) reduction of aphids was recorded in neem oil, clothianidin and flonicamid sequential spray. The sequence chlorpyriphos, flonicamid and clothianidin achieved superior efficacy against jassids with 32.3% reduction over control during the two seasons. The highest reduction (25.2%) of thrips was observed in neem oil, clothianidin, flonicamid sequential spray. The incidence of whitefly was low during the experimental period, however, the highest white fly reduction (15.0%) was observed in chlorpyriphos, flonicamid, clothianidin spray. The lowest number of PBW larvae per 10 green bolls was observed in profenophos, spinetoram, chlorpyriphos+cypermethrin sequential spray that reduces up to 61.9% incidence. The lowest number of (38.5) damaged locules per 100 fully opened bolls were observed in profenophos, spinetoram, chlorpyriphos+cypermethrin sequential spray. But, the highest seed cotton yield (1414 kg ha-1) as well as benefit cost ratio (1.02) was recorded in chlorpyriphos, flonicamid, emamectin benzoate, clothianidin, indoxacarb+acetamiprid sequential spray. The study further revealed that, initial control of sucking pests menace especially jassid was crucial in deciding the cotton yield as compared to later stage pink bollworm menace. During both the years, it was noticed that during peak incidence of jassid, the treated plot with flonicamid against jassid in first instance had given highest seed cotton yield.

Effect of host plants on the oviposition preference of pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Pink bollworm (Pectinophora gossypiella (Saunders, 1843)) (Lepidoptera: Gelechiidae) is an important pest of cotton. We aimed to study the effect of different host plants on the oviposition preference of pink bollworm under laboratory conditions. Cotton (Bt and non-Bt), okra and hibiscus plants were used, which vary in morphological characteristics. Significant differences were observed in the density of trichomes and it is positively correlated with oviposition behaviour of pink bollworm. In a no-choice test, we recorded a higher number of eggs on Bt and non-Bt cotton plants. In two-, three- and four-choice experiments, pink bollworm preferred to deposit the maximum number of eggs on non-Bt cotton among other host plants. A substantially higher number of eggs were laid on Bt cotton in combinations with okra and hibiscus and a considerably lower number on non-Bt cotton. We recorded fewer numbers of eggs on hibiscus in all combinations. Overall, pink bollworm moths showed greater affinity towards non-Bt cotton plants and deposited the maximum number of eggs there. From the practical point of view, the development of cotton genotypes which are devoid or have a lesser density of trichomes may be a possible solution to reduce the pink bollworm egg load on cotton.

Diet impacts on the biological aspects of pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae) under controlled laboratory conditions

Background Pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae) is a native pest of Asia and preferably invasion on cotton (Gossypium hirsutum L.) crop as a commendatory host plant. Commercially, G. hirsutum is known as white gold and is an important cash crop all over the globe. Limited studies were published to focus on certain dietary compositions against different cotton pests. Therefore, the present study was undertaken in the laboratory under controlled conditions (temperature: 27 ± 2°C and relative humidity: 60 ± 10%) to determine the impact of three different treatment diets (wheat germ meal, okra, and chickpea) on the biological aspects (lifetime, developmental period) of P. gossypiella. Results Results revealed that the shortest larval time of P. gossypiella was observed on the okra feed diet while the longest period was recorded on the wheat germ diet. Meanwhile, the pupation delay was noted on the wheat germ diet. The dietary influence was also observed on adult stages of female and male P. gossypiella (43.00 and 37.50 days respectively) and compared with a standard diet (56.50 and 52.50 days respectively). Furthermore, larval weighed more on the okra and chickpea diet followed by the wheat germ diet, whereas highest pupal weight was observed on the standard diet followed by the chickpea diet and okra diet. Conclusion Developmental parameters were significantly variant across all treatment diets, whereas the higher significant difference was reported on the okra diet. Therefore, the existing data of this study offers fruitful interventions for the future as a modified diet for large-scale and rapid mass production of P. gossypiella larvae.

Constraints and Suggestions of the Cotton Growers in Vidharba for Adoption of Improved Integrated Management Practices of Pink Bollworm

The pink bollworm (PBW) is an insect known for being a pest in cotton farming. In Maharashtra cotton growers are set to lose nearly 13 % of their output due to pink bollworm attacks on the standing crop in major production regions of the state. The impact of PBW attack has been felt the most in regions of vidarbha where cotton is cultivated as the main cash crop. Present study was conducted in six districts of Vidarbha region in Maharashtra considering the maximum area under cotton cultivation namely Buldana, Akola, Amravati, Yavatmal Wardha and Nagpur. A sample of 300 cotton growers were randomly selected from twelve taluka (two taluka from each district).The major constraints faced by cotton growers were non availability of labourers and high wage rate for undertaking the manual work of handpicking of larvae destruction of affected fruiting bodies and removal of rosette flower (95.00 %), non availability of biofungicides Beauveria bassiana at nearby market (90.33%), non availability of good quality pheromone trap & good quality pheromone lure (89.00%). In case of suggestions expressed by cotton growers overcome constraints were availability of biofungicides Beauveria bassiana should made available at subsidized rate nearby market, followed by availability of recommended insecticides should made available at subsidized rate in nearby market (94.33%), the government should made available good quality pheromone trap and lure used for pink bollworm at village level (93.00%), credit facilities should be increased and process should also easy and quick (87.33%).

Constraint Faced by Bt Cotton Growers for Control of Pink Bollworm

The present study on knowledge of Bt cotton growers for control of pink bollworm was conducted in Parbhani district of Marathwada region in Maharashtra State. The data were collected through personal interview with the help of interview schedule by contacting 120 respondents. The data was processed by making primary and secondary tables. The distributional analysis pertaining to age of the farmers indicated that (50.00%) of the respondents belonged to middle age category. It was found that, majority (30.00%) of the respondents belonged to primary education category, majority (54.16%) of the respondents had medium level of area under Bt cotton of respondents, 47.50 per cent of the respondents had semi-medium land holding (2.01 to 4.00 ha), 67.50 per cent of the respondents had medium annual income (Rs.98,000 to Rs 2,98,000). While majority (50.00%) of the respondents had medium level of social participation, 50.00 per cent of the respondents had medium economic motivation, larger proportion (50.00%) of the respondents belonged to medium innovativeness, 41.66 per cent of the respondents had medium risk orientation, 55.00 per cent of the respondents had medium level of farming experience, majority (58.33%) of the respondents had medium level of source of information of source of information, 66.68 per cent of the respondents had medium level source of irrigation, 58.33 per cent of the respondents had medium extension contract.

Effect of different nutrient diets on developmental and reproductive fitness of Pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Pink bollworm, Pectinophora gossypiella (Lepidopetra: Gelechiidae) is one of the most important pest of cotton. In this paper, we studied the influence of different nutrient rearing diets on developmental and reproductive characteristics of pink bollworm under laboratory conditions. Larvae were reared on four diets (two natural diets and two artificial diets) with varied nutritional value. Larval diet affects the survival, development duration, pupal weight, adult emergence and fecundity. Pink bollworm attained the fastest larval development on NRD (19.8 days) with a survival rate of 88.2% and slowest on NPD and okra (~ 27.1 days) with a survival rate of 47.5% and 58.1% respectively. Pupal weight was highest (26.86 mg) on NRD and reached maximum fecundity (107 eggs/female), while lowest fecundity on NPD (37 eggs/female). Among natural diets, egg hatching rate on cotton and okra were 87% and 71%. Adult emergence starts early and the adult eclosion window was narrow on cotton and NRD. Adult longevity was varied with diets, while female moths lived longer than males in all diet treatments. Our study may help to understanding the effect of nutrition from different diets and enhanced the fecundity of P. gossypiella on NRD under laboratory conditions.