Efficacy of Trichogramma evanescens (Hymenoptera: Trichogrammatidae), Six Pesticides, and Their Combinations to Control Pectinophora gossypiella (Lepidoptera: Gelechiidae) in Egyptian Cotton Fields

Pink bollworm, Pectinophora gossypiella Saunders (Lepidoptera: Gelechiidae) is one of the most economically devastating pests of cotton globally. Chemical control is the first line of defense, but has become ineffective in reducing yield losses caused by this pest. New management strategies against pink bollworm is urgently needed. Field evaluations were conducted using the six pesticides were tested in two cropping seasons at a single dose, corresponding to their maximum recommended field rate of cotton in Egypt either with or without the egg parasitoid Trichogramma evanescens, TE (Hymenoptera: Trichogrammatidae). Treatments were applied to plots of cotton in 27th and 20th of July, 2021 and 2022, respectively, against pink bollworm, and efficacy was calculated based on the plant damage caused by the larvae through the yield. The highest reduction in pink bollworm larval numbers along with the least boll damage were found in azadirachtin, chlorantraniliprole, or hexaflumuron + T. evanescens (TE) plots. During both years, it was observed that plots treated with biological control agent and some pesticides led to a significant increase in cotton yield. The parasitism rates were 28.88, 24.19, 23.66, and 20.13% in the plots treated with azadirachtin, hexaflumuron, chlorantraniprol, and spinosad and only 2.80 and 1.57% in the plots treated with lambda-cyhalothrin and profenofos versus 33.62% in the control plot, there was difference significantly among treatments (p ≤ 0.05). These findings underscore the potential use of TE combined with pesticides (mainly azadirachtin) to control pink bollworm larvae. The promising results were achieved when combined TE with azadirachtin, the combined treatment significantly decreased the population of the pink bollworm and crop damage.