Effects of entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis bacteriophora on the fitness of a Vip3A resistant subpopulation of Heliothis virescens (Noctuidae: Lepidoptera)

Abstract

The widespread use of transgenic plants imposes selection pressure on insect pest populations to develop insecticide resistance. Evaluation of effectiveness of resistance management strategies is very important in resistance management programs. Resistance management to insecticides is widely believed to depend in part on associated fitness costs. Fitness costs can delay the development of resistance. In the present study, the effects of two entomopathogenic nematode species, Steinernema carpocapsae and Heterorhabditis bacteriophora were studied on the fitness of first insect population of Heliothis virescens selected with Vip3A in the laboratory. It was found that both nematodes species increased the fitness cost of Vip3A selected insects. The mortality of the Unsel subpopulation after exposure to either nematode species was significantly lower than that of the Vip3A-Sel subpopulation. Likewise, the reproduction of both nematode species was significantly greater in cadavers of the Unsel compared with the Vip3A-Sel subpopulation of H. virescens. There was positive correlation between nematode reproduction and the larval instar infected with nematodes. The penetration of infective nematode juveniles (IJ) was greater in the Vip3A-Sel subpopulation than in the Unsel subpopulation of H. virescens. It is concluded that entomopathogenic nematodes could increase the fitness costs and subsequently delay the resistance.

Characterization and Pathogenicity Test of Entomopathogenic Nematode Steinernema Species-Kalro

“…The decrease in mortality at higher IJs concentration could be attributable to competition for entry points, penetration ability, and virulence of nematode in the petri dish bioassay. According to Gulzar et al (2020), IJs penetration and virulence influence nematode pathogenicity.…”

Evaluation of Transgenic Cotton Cultivars Containing Cry Toxins From Bacillus Thuringiensis Against Thrips

“…Cry proteins show lethal properties and cause the death of targeted insects without any harmful effects on vertebrates and plants. Bt is used as an excellent alternate method to control pests and diseases (Bravo et al, 2005;Gulzar et al, 2020). Cultivation of Bt cotton on a large area is changing the pest situation because Bt cotton is an excellent source for controlling the chewing pests and reduction of pesticides cost.…”