Abstract
In 2000 and 2001, studies were carried out to evaluate the influence of predators on the cotton aphid, Aphis gossypii Glover (Homoptera: Aphididae), in Xinjiang Uygur Autonomous Region, China, where alfalfa was mainly planted as an intercrop with cotton. There were 25 species of predators observed from June to August; 16 species of predators were caught in both cotton and alfalfa. Predators were classified into five groups: predatory beetles, lacewings, predatory bugs, syrphid flies and spiders. The total number of predators in alfalfa was 2.45 times and 20% more than that in cotton in 2000 and 2001, respectively. In an alfalfa-cutting experiment, it was found that predators increased significantly faster in cotton bordering the alfalfa-cutting treatment than in the non-cut control, and the growth of the cotton aphid population was delayed in a cotton field adjacent to the treatment compared to that adjacent to the control. This indicates that alfalfa-cutting induces predator immigration into adjacent cotton fields and helps control cotton aphids. The impact of alfalfa cutting on predators and cotton aphids was evident for about 14 days.
