(STUDIES ON SOME FACTORS AFFECTING THE POTENTIALITY OF CHEMICAL CONTROL OF THE COTTON LEAFWORM Spodoptera littoralis (Boisd

Abstract

The present study was carried out, aiming to investigate some factors for improving chemical control of the cotton leafworm S. littoralis through -- two approaches : 1. Searching for some plant species (weeds) having naturally occurring biologically active compounds to be extracted and used either as alternatives to synthetic pesticides or/and as synergists in mixture with these pesticides. 2. Reducing the amount of a.i. of chemical pesticides used in pest control through synergism resulted by addition of several acids to the formulated pesticides. For achieving both targets 16 weed plant species were explored for the first approach whereas 22 inorganic and organic acids were tested in the second part. The obtained results could be summarized in the following : I. Toxicological and Biological effects of feedingS. littoralis larvae on fresh leaves of weed selecteds 1. Feeding the 4th instar larvae on fresh leaves of the tested weeds resulted in 100% larval mortality in 9 out the 16 weed plants. Also, larval duration was significantly prolonged in 4 out of 16 recording the maximum by Medicago hispida and Vicia monantha. 2. The pupation percentage was significantly reduced in 7 treatments - that survived after larval feeding and pupated, the maximum reduction in pupation was recorded in Beta vulgaris (3%) and Raphonus sativa var. surtus (4%).