NEW APPROACHES FOR CONTROLLING THE COTTON LEAFWORM AND BOLLWORMS IN RELATION TO ABUNDANCE OF PARASITOIDS AND PREDATORS

Abstract

Efficacy of a bioinsecticide (Xentari), a chemical insecticide (Baytbroid), an IGR (Mimic) and a combination of Xentari +LC10 ofBaythroid or Mimic was assayed on parasitised Spodoptera littoralis larvae by Microplitis rufwentris. Treated larvae showed lower mortality percentages, higher LC50 and longer LT50 than the unparasitised ones lowest concentration of Xentari (4x104 DBMU)+ LC10 of Baythroid caused 16.67 and

23.33 % mortalities among parasitised and unparasitised larvae, respectively, and the mixture showed potentiative effect. Also, the mixture of 4x 104 DBMU of Xentari + LC10 of Mimic led to 30.00 and 33.33 % mortalities, respectively, and showed also

potentiative effect. Two successive years (1998 and 1999) of field studies indicated the presence of 13 predaceous insect species, 6 S. littora/is parasitoids and 3 bollworm parasitoid species in cotton fields. Weekly estimations of populations of each species were made by sweeping net and true parasitism methods. Chemical insecticidal applications caused severest effect on entomophagous insects, while Xentari (Bacterial insecticide) and Clerodendron inerme extract were safe on these beneficial insects. Also, sex- pheromones had no hannful effect on predators and parasitoids. For S. littora/is and bollworms control.