Differential Feeding Parameters of Spodoptera littoralis on Beet Type Leaves treated with Insecticides

Cotton leafworm, Spodoptera littoralis (Boisd.) is a major lepidopteran pest of beet types in Egypt. The present investigation was conducted to determine the effect of three beet types; sugar, table and fodder beet on feeding S. littoralis in addition to the toxic effects of three insecticides, Protecto 9.4% WP (Bacillus thuringiensis), Speedo 5.7 % WG (emamectin benzoate) and winsor 24% SC (methoxyfenozide) under semi-field conditions. This study was carried out in 2023 and 2024 seasons, at Sakha Agricultural Research Station. Results revealed that the lowest area of the leaf consumed by S. littoralis after 24 h was significantly recorded in both fodder and sugar beet type treatments; it was 1.10 and 1.29 cm2 /larva, respectively. Feeding percentage rate of 4th instar S. littoralis larvae fed on different beet leaves treated with Protecto, Winsor and Speedo at 1/2 and 1 field rates was decreased. At 1/2 recommended rate after 24 h, the lowest area of the consumed leaf and feeding percentage were significantly recorded in Speedo treatment on table beet 0.59 cm2/ larva and 2.99%, respectively. Based on the nutritional values of testing beet types, results proved that table beet was the most favorable type for S. littoralis due to the differences in the leaf nutritional quality and low level of total phenol in the leaves of table beet. This research aims to determine the most effective and sustainable method for controlling S. littoralis by comparing the tolerance of different beet types with the efficacy of various insecticides.