Combined Effect of Entomopathogenic Fungi, Beauveria bassiana and Certain Insecticides for the Control of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) under Semi-Field Conditions

This study was carried out at Quesna district, Menoufia governorate during 2017 growing season under semi field conditions against 2^nd and 4^th instar larva of Spodoptera littoralis (Boisd.) to evaluate the efficiency of combining Beauveria bassiana with certain insecticides (emamectin benzoate, methomyl and Bacillus thuringiensis) in tomato field. In general, data revealed, clearly, that methomyl had the highest efficacy against 2nd larval instar, where, the percentages corrected mortality were 98.28, 62.68 and 27.09% at concentrations RC,1/2RC and 1/4RC respectively. While, when 4^th larval instar treated by emamectin benzoate, the observed total percentage corrected mortality was the highest value (90.54%) at RC followed by methomyl (85.79%) at RC, whereas, when treated 2^nd and 4^th larval instar with fungi had the lowest values of percentage corrected mortality at all concentrations compared with remaining treatments. When treated larvae with mixture of fungi (B. bassiana) and insecticides percentages mortalities of second and fourth larval instar of emamectin benzoate + B. bassiana and methomyl + B. bassiana had the highest values after 24hrs. then decreasing gradually, but the highest values of percentage mortality of second and fourth larval instar when mixtures of Bacillus thuringiensis + B. bassiana were after fifth days at concentrate of insecticide 1/2RC and after third day at concentrate of insecticide 1/4RC. So mixing increases the efficiency of their insecticides.