HISTOPATHOLOGICAL STUDIES ON THE EFFECT OF SOME ALTERNATIVE INSECTICIDES ON Spodoptera littoralis (Boisd.)

The insecticidal activity biological and histological effects of a bacterial bioagent spinosad (24% SC), an insect growth regulator methoxyfenozide (24% SC) and extrem (36 % SC), Ready-made mixture (Spinetoram 6% and methoxyfenozide 30%) on the 4th larval instar of the cotton leaf warm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), under laboratory conditions, as denoted by the determined LC50 which was 7.28, 0.071 and 0.113 ppm, in spinosad, methoxyfenozide and extrem, respectively. The highest rate of decrease in the pupation percentage of 25% was recorded in case of treated with extreme followed by spinosad and methoxyfenozide (76 and 63 % respectively). Also, the adult emergence rate was remarkably reduced in case of extreme to 40% followed by spinosad 56.6% and methoxyfenozide 69.8%. The male moths recorded lower rate of adult longevity than the female moths. On the other hand both toxicants induced drastic effect on fecundity and fertility of adult moths. Highly histopathological disturbances in the midgut of this pest including destruction of the muscle layers, disorganization in the epithelial cells, separation of the peritrophic membrane as well as detachment of the basement membrane and appearance of vacuolizations. Also caused severe histological aberration of the ovarioles.