The effectiveness of some selected insecticides against cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) and their non-targeted predators

Abstract

The invasive polyphagous cotton mealybug, Phenacoccus solenopsis Tinsley has emerged as a serious sucking pest of cotton. The laboratory and field bioassays of seven selected insecticides belonging to five toxicant groups were evaluated against P. solenopsis and their most abundant natural predators, Chrysoperla carnea (Steph.) and Hyperaspis vinciguerrae Capra. Based on the toxicity index the most toxic group of insecticides under laboratory conditions was esfenvalerate, acetamiprid and dimethoate after 24 h and 72 h of treatment followed by the oxadiazines metaflumizone, indoxacarb and finally the anti-moulting IGRs, diflubenzuron and chlorfluazuron against the 3rd instar nymphs of P. solenopsis using spraying method technique. Of the selected insecticides, dimethoate was significantly superior over the rest of treatments with a highest average reduction percentage in cotton mealybug population (98.26%) under field conditions followed by esfenvalerate (96.72%), indoxacarb (89.66%), metaflumizone (89.43%), acetamiprid (86.28%), diflubenzuron (81.51%), and the least one chlorfluazuron (76.82%). Field experiments recorded that the anti-moulting IGRs were the safer toxicants towards C. carnea with average reduction diflubenzuron (45.99%) and chlorfluazuron (25.68%) and towards H. vinciguerra, were diflubenzuron (49.39%) and chlorfluazuron (41.52%).