POPULATION FLUCTUATION OF SOME PIERCING-SUCKING INSECTS AND ITS RELATION TO ASSOCIATED PREDATORS AND THE PREVAILING WEATHER FACTORS IN SOYBEAN FIELDS AT KAFR EL-SHEIKH GOVERNORATE.

In Egypt, aphids, Aphis spp.; leafhoppers, Empoasca spp. and whitefly, Bemisia tabaci (Genn.) are the most important piercing-sucking insect pests infesting soybean plants and a good understanding of their population dynamics is essential to develop an integrated pest management strategy. Therefore, the population densities of these insects and its relation to the common associated predators and the prevailing weather factors were investigated in soybean fields at Kafr El-Sheikh Governorate for 2016 and 2017 seasons. Weekly counts of the considered insects per 15 leaves indicated that whitefly was the most abundant species followed by leafhoppers, while aphids were the least one. Whitefly and leafhoppers appeared on soybean plants all over the growing season. The maximum density of whitefly took place from mid-June to late July in the first season and from the second half of July to the first half of August in the second season. The high number of leafhoppers occurred in the period from mid-July to mid-August for the first season and during August in the second season. Aphid population appeared only in two periods with very low numbers for every season. In the first season, the first period occurred in the second half of June, while the second period took place in the first half of September. In the second season, the In Egypt, aphids, Aphis spp.; leafhoppers, Empoasca spp. and whitefly, Bemisia tabaci (Genn.) are the most important piercing-sucking insect pests infesting soybean plants and a good understanding of their population dynamics is essential to develop an integrated pest management strategy. Therefore, the population densities of these insects and its relation to the common associated predators and the prevailing weather factors were investigated in soybean fields at Kafr El-Sheikh Governorate for 2016 and 2017 seasons. Weekly counts of the considered insects per 15 leaves indicated that whitefly was the most abundant species followed by leafhoppers, while aphids were the least one. Whitefly and leafhoppers appeared on soybean plants all over the growing season. The maximum density of whitefly took place from mid-June to late July in the first season and from the second half of July to the first half of August in the second season. The high number of leafhoppers occurred in the period from mid-July to mid-August for the first season and during August in the second season. Aphid population appeared only in two periods with very low numbers for every season. In the first season, the first period occurred in the second half of June, while the second period took place in the first half of September. In the second season, the population appeared from late June to mid-July and from late August to mid-September. Also, three predaceous insect species: Chrysoperla carnea (Steph.); Coccinella undecimpunctata L. and Orius spp. were observed on soybean plants. Ch. carnea was the most abundant predator, while C. undecimpunctata was the least one. The total of the predaceous insects attained the highest numbers during July in the first season and during July and August in the second one. The weather factors (temperature, relative humidity and wind speed) had insignificant effect on the cotton whitefly population in the two study seasons. As for leafhoppers, wind speed only had significant effect on the population activity in the second season. Temperature and wind speed in the first season and wind speed in the second season had highly significant effect on aphids activity in the first season. The effect of the predators on the insects was insignificant during the two seasons except effect of the predaceous insects on the leafhoppers which it was significant. The combined effect of both predators and the prevailing weather factors was more pronounced only on aphids in the first season and on leafhoppers in the second season. However, the gained results may provide valuable information for comprehensive integrated insect management of soybean. [ABSTRACT FROM AUTHOR]