EFFECT OF PLANTING DATE ON POPULATION ABUNDANCE OF CERTAIN LEAF PESTS INFESTING SOME VEGETABLE CROPS AT GEMMEZA REGION, EGYPT

Planting potato in summer and winter seasons as well common bean and squash during summer and nit plantations were practised to show their effects on occurrence of /Viols gossypii Glover, Aphis cracci‌vora Koch, Myzus persicae Sulz., Empoasca decipiens Paoli, Thrips tabaci Lind., Bemisia tabaci (Genn.) ant Tetranychus sp. infesting leaves of the above mentioned vegetable crops during the two successive years 1991 and 1 992 at Gemmaza region, Egypt. The obtained results showed that the population density of B. tabaci and Tetranychus sp. on potato plants grown in the winter season was higher than in summer, while the oppo‌site was true in case of the other pests . In both summer and nili plantations of 1991 and 1992, the sow‌ing date of common bean plants had a significant effect on the inci‌dence of all pests except for M. persicae duirng the nili season of 1991 which was insignificantly influenced by changing the time of sowing. The third sowing date, mid-April (summer) and mid-September (nili) was more suitable for common bean cultivation showing the highest yield and recording relatively low number of most of the studied pests. Pests that occurred on summer squash plants were highly in‌fluenced by the date of sowing . In case of nili plantation , the differenc‌es between the population density of A. craccivora and T. tabaci in 1991 and M. persicae in 1992 attacking squash plants sown at five intervals were statistically insignificant. The fourth summer sowing date (mid-May_ and the third nisi one (mid-September ) for squash vegetable crop were recommended, because they gave the highest yield and showed the lowest population of all pests except for Tetranychus sp. and B. tab‌aci during the summer season of 1991 and nili season of 1992, respec‌tively.