[Ecological control effects of Litchi chinensis-Desmodium intortum complex plant ecosystem on litchi pests]

An investigation on the community structure and dynamics of litchi pests and their natural enemies in constructed Litchi chinensis-Desmodium intortum complex plant ecosystem and single L. chinensis ecosystem showed that the total amount of litchi pests in the complex plant ecosystem was 61.27% of that in the single ecosystem in whole year, and only 50.45% in May, the key time for fruit development, which suggested that there was an interaction between D. intortum and L. chinensis. D. intortum and L. chinensis had a few common pests, but many common natural enemies. D. intortum florescence in winter provided shelter and substitutive food for the natural enemies of pests to survive in the extreme environmental conditions in winter. L. chinensis florescence was on the heel of D. intortum florescence, which provided better conditions for the natural enemies to survive and multiply. During florescence and fruit development stages of L. chinensis (from March to June), the predator/prey ratio in complex plant system was 4.22, 2.34, 2.2 and 20.63 times of that in single plant system in March, April, May and June, respectively, indicating the good control effect on pests of L. chinensis.