Effect of treated and untreated cotton fields with pesticides on the population fluctuations of the most important cotton pests and their associated insect predators

The cotton variety Gossypium barbadense was planted in experimental fields during the March (2022, 2023, and 2024) seasons, and the studies continued for five months. Field studies were carried out at El-Zagazig distract Sharkia Governorate to compare the effect of insecticide-treated and untreated cotton fields on average monthly numbers, the seasonal fluctuations of the most important cotton pests, and the common insect predators associated with cotton pests. The results showed that the treated and untreated cotton fields significantly affected the average monthly numbers of the four cotton pests Aphis gossypii, Bemisia tabaci, Spodoptera littoralis, and Pectinophora gossypiella and five associated common insect predators Chrysoperla carnea, Coccinella undecimpunctata, Scymnus spp., Orius spp. and Paederus alfierii during the three cotton seasons. Furthermore, the average monthly number of the four cotton pests and their accompanying predators in untreated cotton fields was greater than that of those treated with pesticides. The fluctuations of four insect pests in the treated and untreated cotton fields were recorded at 53 peaks; it was 24 peaks in the treated fields and 29 in the untreated fields. On the other hand, predators recorded 41 peaks; 18 were in treated fields and 23 in untreated fields. Thus, it is clear our study showed S. littoralis was the most common of the four pests, and C. carnea was the most common predator of the five predators in both treated and untreated cotton fields. Thus, the study recommended that preserving natural enemies is a key tactic in IPM.