Insect Pests and Natural Enemies Associated with Berseem (Trifolium alexandrinum L.) in Cotton Field

摘要

Berseem clover (Trifolium alexandrinum L.) is annual winter leguminous forage it also known as trap crop which attract the predators and parasitoids of insect pests. The irrational use of pesticides reduced pests and natural enemies and destroyed the delicate balance between pests and predators in field crops. The study was carried in Rabi growing season during 2012. The cotton was sprayed with highly hazardous pesticides for pest control, after the harvesting of cotton, 25 kg/ha barseem seeds were broadcast in irrigated soil beds. Barseem crop was investigated for pest and natural enemies on every week, 5 plants checked at 20 different locations after 14 days (2 weeks) of germinations and 13 week were recorded throughout the three cutting periods. Insect pests, which appear on berseem crop, were: aphid, leaf minor, dusky bug, thrip, whitefly, crocket, and cutworm, their populations varied with one another during whole study period. The average pest populations were recorded aphid, leaf minor, dusky bug, thrip, whitefly, crocket, and cutworm (6.18, 0.56, 0.45, 0.35, 0.33, 0.21, and 0.49 respectively). Whereas the natural enemies were; rove beetles, lady bird beetle, ant, spider, big eyed, and green lace wing (1.83, 1.31, 0.70, 0.63, 0.34, and 0.15 respectively). In berseem agro ecosystem at cotton field showed that some cotton pest were occurred on berseem and infest the crop in the initial period of growth and when the climate was become cold and natural enemies appear in agro ecosystem of berseem these pests were controlled. Keywords: Pests, Natural Enemies, Berseem, Cotton