الفهرس 
InsecticidesOnly 14 pages are availabe for public view
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Abstract
Comparison of toxicity levels of cotton leafworm field population collected during 1978, 1979 and 1Y80 cotton growing seasons with those of a normal laboratory (susceptible) strain was made. The susceptibility of the secohd and fourth instar larvae of the laboratory strain of Spodoptera littoralis to sex insecticides was determined. Both larvae showed high response to Decis, Ripcord, Sumicidin, Chlorpyrifos, Cyolane and Cytrolane in descendine order. When the dosages for the different weight larvae were calculated as ~g/g. body weight, it was found that the fourth instar larvae were more susceptible to tested insecticides than the second instar larvae. The second instar larvae were found to contain high lipid content than the fourth instar larvae. Therefore, the tolerance of the second instar larvae may be due to their high lipid ~ontent. The population of Kafr El-Sheikh strain acquired considerable resistance to Chlorpyrifos (10.4 X) in the 1979 cotton growing season. The resistance ratio of Chlorpyrifos decreased to (6.3 X} in 1980. The resistance to Cyolane showed a low level of tolerance (4.8 X) 1978 and a 7.2 X level of tolerance in 1979. Concerning the resistance to Cytrolane no significant detectable changes were observed in resistance ratio in 1978, 1979 and 1980.