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Abstract The present work was conducted out at Shandweel Agricultural Research Station to study the effect of releasing of 2nd larval instars of Coccinella septempunctata L. and chrysoperla carnea Stephens on the infestation of common bean plants with Aphis craccivora Koch. and its associated insect predators during two successive seasons (2010 and 2011). The population densities of Aphis craccivora and its associated insect predators were studied. Also, correlations between aphid and its associated insect predators was evaluated. In addition, the effect of the prevailing weather factors of area on the populations of Aphis craccivora and its associated insect predators were analyzed. Finally, three laboratory studies were performed: (1) effect of Aphis craccivora density on daily and total consumption and development of Coccinella undecimpunctata L., Coccinella septempunctata and chrysoperla carnea larvae, (2) predation upon Aphis craccivora by Coccinella undecimpunctata, Coccinella septempunctata and chrysoperla carnea larvae in the presence and absence of Bemisia tabaci (Genn) and Empoasca decipiens (Paoli) nymphs, and (3) effect of alate and apterous Aphis craccivora on the feeding potential of Coccinella undecimpunctata, Coccinella septempunctata and chrysoperla carnea larvae. The results could be summarized as follow: 1- Field studies: 1.1- The population densities of Aphis craccivora infesting common bean plants and its associated insect predators during 2010 and 2011 seasons. The obtained results revealed that alate, apterous and total number of A. craccivora formed 2, 1 and 1 peaks, respectively, in both seasons. Coccinella undecimpunctata eggs, larvae, pupae, adults and total number maximized 1, 1, 2, 2 and 2 times, respectively, in 2010 season, and 2, 3, 2, 2 and 1 times in 2011 season. The eggs, larvae, pupae, adults and total number of Ch. carnea formed 2, 2, 1, 3 and 2 peaks, respectively, in 2010 season, and 2, 1, 1, 3 and 2 peaks in 2011 season. The mean of nymphs, adults and total number of O. spp. were observed to form 1, 1 and 2 peaks, respectively, in 2010 season, and 1, 1, 1 peaks, respectively, in 2011 season. The weekly average number of Scymnus spp. larvae adults and total number formed 1, 2 and 2 peaks, respectively, during 2010 season, and formed 2, 2 and 2 peaks, respectively, during 2011 season. The populations of Syrphus corollae (F.) larvae, pupae and total number peaked one time in 2010 season, and peaked 2, 1 and 1 times, respectively, in 2011 season. 1.2- The correlations between Aphis craccivora infesting common bean plants and its associated insect predators. Highly significant positive correlation values were found between the numbers of C. undecimpunctata eggs and larvae in side and aphid numbers on the other side in both seasons of the study. However, the correlation between aphid and adult numbers was highly significant positive in 2011 season, only. Concerning, Ch. carnea, significant and highly significant positive correlation values were found between the numbers of aphid and lace wing eggs and larvae, respectively, in 2010 season. The correlation between S. spp. larvae and A. craccivora numbers was found to be highly significant and significant positive in 2010 and 2011 seasons, respectively. No significant correlations were found between A. craccivora numbers and other insect predators in both seasons. |