Susceptibility of Chilo partellus Swinhoe, 1885 (Lepidoptera: Crambidae) to some commonly used insecticides

Abstract

Chilo partellus Swinhoe, 1885 (Lepidoptera: Crambidae), a destructive pest of maize, was recently recorded in the Mediterranean Region of Turkey. The pest is considered to be an invasive species, displacing indigenous stem borers in many parts of the world. The aim of the study was to determine the effect of commonly used insecticides in a maize production system in Turkey on egg hatch and mortality of first instar larvae of C. partellus under laboratory conditions (27±2ºC, 70% RH and 14:10 h L:D photoperiod) at the Plant Protection Department, Faculty of Agriculture, University of Çukurova. Eight insecticides registered for indigenous lepidopteran pests were used at the recommended rates. The percentage of hatched egg masses were significantly different. The smallest percentage was 30.6% with deltamethrin. The percentages of hatched egg masses were greater than 80% for all other insecticides. Mortality of hatched larvae was significantly different. The highest and lowest mortalities of hatched larvae were 84.5% and 38.2% with emamectin-benzoate and lambda-cyhalothrin, respectively. Seventy-two h after exposure of the first instar larvae to sprayed maize leaf disks, the lowest and highest mortalities were 62.6% and 96.7% with indoxacarb and emamectin-benzoate, respectively. Survival analyses revealed that hazard ratios ranged from 4.91 (95% CI: 1.66-14.6) to 15.6 (95% CI: 5.33-45.6) with chlorpyrifos-ethyl and emamectin-benzoate, respectively. The mortality of first instar larvae was about 16, 10 and 9 times that of the control with emamectin-benzoate, lambda-cyhalothrin and deltamethrin, respectively. Feeding activity of larval stage was reduced by all treatments. The implications of this study are discussed.