(HISTOPATHOLOGICAL AND BIOCHEMICAL EFFECTS OF SOME INSECTICIDES ON THE LESSER COTTON LEAFWORM SPODOPTERA EXIGUA HB. (LEPIDOPTERA : NOCTUIDAE

Abstract

It is necessary to emphasize the economic importance of• the lesser cotton leafworm, Spodoptera exigua (Hb.) as an economic pest attackin& several crops and vegetables in Egypt.

The present study was undertaken to investigate the effects of Dimilin (insect '

growth regulators), Malathion (organophosphorus compound) and Cypermethrin ' (synthetic pyrethroid) in terms of the biological, biochemical ana histopathological

responses on S. exigua. Results could be summarized as follows:

I - Biological studies:-

Treatments were carried out on the fourth instar larvae, beca se of its moderate 'i s1ze which facilitates its handling, and the observations were undertaken on the fifth

instar larvae and on adults emerged from the treated stage. The•8iological effects of insecticides appeared in the following:-

a- Prolongation in the duration of larval and pupal stages.

b- Malformation percentages recorded in larvae, pupae and ai!ults treated as 4th I - I larval instar increased progressively with increasing the dose of treatment.

c- Percentage of larval mortality was dose-dependent i.e. increaled with increasing 'I dose of the three different insecticide groups. 1

d- The pupation and adult emergence percentages decreased anthis decrease was

highly increased in case ofCypermethrin treatment.