PREDATORS AND THEIR ROLE IN CONTROLLING APHID POPULATION

Aphis craccivora Koch and Aphis gossypii Glover are considered as main pests of some vegetable crops as cowpea and cucumber, in Egypt. The population dynamics of the two pests and three predators associated with them were studied For the two growing seasons 1994 and 1995 in Qualyobia Governorate. The highest population of A.craccivora on cowpea was observed on May, while the lowest was re­corded on June. As for the highest population of A.gossypii on cucum­ber, the same trend of the above mentioned aphid species obtained. Three predators, namely Coccinella undecimpunctata, Scymnus interrup­tus and Onus albrdipennis were recorded associating with the aphids on both cowpea and cucumber . They caused a reduction in A.craccivora population by 55.64 % and 59.4% on cowpea or by 82.64% and 73.62% in A.gossypii on cucumber. This indicate that Cundecimpunctata had a strong effect in minimizing A.craccivora (1:67.58 or 88.90), while Onus albidipennis had an effective role in decreasing A.gossypri on cu­cumber (1:11.22 or 13.9). Data indicate that the most active period for the three predators on the two hosts was recorded during the sec­ond half of May uptil the end of the first week of June.