الفهرس 
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Abstract
The aim of this study was to find a new effective compounds against the 2nd and 4th instars larvae of cotton leafworm Spodoptera littoralis (Boisd). A different groups of pesticides were tested in this study e. i. the insecticides (pyridalyl-spinetoram), the IGR (indoxacarb) and the biocide (Bacillus thuringiensis) in the laboratory and under the field conditions. Also, two natural products lemon juice and clove oil were tested for their toxicity against the 2nd instar larvae of the same insect.
Results in the laboratory studies showed that Spinetoram was the most effective compound against the 2nd instar larvae. While for the 4th instar larvae (pyridalyl and indoxacarb) were more effective. Also, lemon juice showed more effective than clove oil against the 2nd instar larvae . For the semi-field experiments the obtained data focused that spinetoram was the most effective compound. The joint action effective between (Lemon juice or Clove oil) with the previous tested compounds were tested at the level of LC50 and LC25 values. Results showed that there was an antagonistic effect against the 2nd instar larvae of cotton leafworm.
Indoxacarb or B. thuringiensis showed a decreasing in AchE activity of 40% after 24 hrs, While pyridalyl showed a decreasing of 20%, also, spinetoram showed a decreasing of 40% after 21 days. For total protein content it was a decreasing in the group treated with spinetoram at intervals up to 21 days. While for B. thuringiensis group, it was decreased at the end of the experimental period with 28% decreasing. Also, pyridalyl was decreased in the beginning and return to it’s normal rate at the end of the experimental period.