Field Efficacy, Sub-lethal, and Biochemical Effects of Certain Biorational Insecticides Against the New Intruder, Spodoptera frugiperda in Bani-Suef, Upper Egypt.

Abstract

Frequent inspections on sorghum and maize crops during seasons of 2021 and 2022 in some regions in Bani-Suef governorate, Egypt, discovered unprecedented invasions of Spodoptera frugiperda (J. E. Smith). Accordingly, our study on Beauveria bassiana and spinetoram was supporter to the Food and Agriculture Organization's tendency in adopting biorational insecticides against S. frugiperda in Egypt. Exposure toxicity of LC25 values at 48h of B. bassiana were 2.7 × 106 and 5.2 × 106 conidia mL-1 and spinetoram were 0.019 and 0.048mg L-1 against the 2nd and 4th instar larvae laboratory strain of S. frugiperda, respectively. Sub-lethal effects (LC25) were accomplished on biological parameters against both instar larvae. LC25 of B. bassiana reduced adult emergency (89.91 and 91.05%) more than spinetoram (75.99 and 79.49%) against the 2nd and 4th instar larvae, respectively. The 2nd instar larvae exposed to LC25 of B. bassiana suppressed female fecundity (0.00 eggs) more than spinetoram (19.74 eggs). Enzymatic activity of lipase in hemolymph, fat bodies, and mid-gut of the 4th instars at 48h showed significant drop in B. bassiana more than spinetoram. Glutathione-S-transferase (GST) levels in hemolymph for both insecticides were equal and exceeded the control. Fat bodies and mid-gut possessed the highest GST activity in B. bassiana followed by spinetoram and the control. Residual efficacy of spinetoram exceled B. bassiana at their field rates under semi-field condition in Bani-Suef along the two seasons of maize crop against both instars. Eventually, B. bassiana alongside spinetoram could afford good control especially on early instar larvae of S. frugiperda.