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.

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.

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.

Virulence of Beauveria bassiana and Metarhizium anisopliae on different stages of the pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

Background The pink bollworm, Pectinophora gossypiella, is the most destructive pests of the cotton plant in Egypt. Due to the several problems of insecticides, the present study was conducted to evaluate the toxicity effect of the entomopathogenic fungi (EPF), Beauveria bassiana and Metarhizium anisopliae, against the different stages of the pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) Results The fungal isolates exhibited a toxic effect against the treated stages, egg, larva, and pupa. According to the obtained data of LC50, B. bassiana was more potent in inducing toxicity than M. anisopliae. However, eggs of P. gossypiella were less susceptible to the EPF than the other stages. Based on total mortality, LC50 was 4.97×1011, 6.03×1012 spores/ml for egg; 8.25×108, 6.03×109 spores/ml for neonate; 2.52×108, 1.29×1010 spores/ml for early 4th instar larvae; and 6.79×108, 8.36×109 spores/ml for pupae after treatment with B. bassiana and M. anisopliae, respectively. Conclusions Entomopathogenic fungi exhibited an activity in inducing mortality against different stages of P. gossypiella.

Novel RNA Viruses from the Transcriptome of Pheromone Glands in the Pink Bollworm Moth, Pectinophora gossypiella

In this study, we analyzed the transcriptome obtained from the pheromone gland isolated from two Israeli populations of the pink bollworm Pectinophora gossypiella to identify viral sequences. The lab population and the field samples carried the same viral sequences. We discovered four novel viruses: two positive-sense single-stranded RNA viruses, Pectinophora gossypiella virus 1 (PecgV1, a virus of Iflaviridae) and Pectinophora gossypiella virus 4 (PecgV4, unclassified), and two negative-sense single-stranded RNA viruses, Pectinophora gossypiella virus 2 (PecgV2, a virus of Phasmaviridae) and Pectinophora gossypiella virus 3 (PecgV3, a virus of Phenuiviridae). In addition, sequences derived from two negative-sense single-stranded RNA viruses that belong to Mononegavirales were found in the data. Analysis of previous transcriptome sequencing data derived from the midgut of pink bollworm larvae of a USA population only identified PecgV1, but no other viruses. High viral sequence coverages of PecgV1 and PecgV4 were observed in both field and lab populations. This is the first report of viral sequences discovered from the pink bollworm. Results from this investigation suggest that the pink bollworm harbors multiple viruses. Further investigation of the viral pathogens may help to develop novel pest management strategies for control of the pink bollworm.

Incidence of Pink Bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) on Flowers (Rosette) of Bt Cotton in Andhra Pradesh, India

The pink bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) has recently emerged as a serious menace on Bt cotton in India. Extensive roving surveys were conducted in 12 locations of three major cotton growing districts of Andhra Pradesh, India, to assess the level of pink bollworm infestation in Bt cotton during 2018-19 and 2019-20. The dynamics and severity of flower damage due to pink bollworm during the 60-135 days’ crop period were evaluated based on a random sampling of flowers. Survey results revealed a widespread infestation of pink bollworm on Bt cotton flowers across the surveyed sites in a range of 11.8-19.50%. With the advancement of the crop season, a progressive increase in the flower damage was observed till 120 DAS then declined. Reasons for the enhanced flower damage and implications are discussed in this article.