To understand the ecological impact both intercropped herbages and management methods in jujube plantation on natural enemies and Ancylis sativa, during March 10 to September 30 in 2004 a systematic survey was conducted under four treatments toward the jujube trees that were all in 10-years old and in full fruit production in a jujube plantation that is located 2.5 km west of Taigu (111°32′E, 37°26′N, 781.9 m elevation) in Shanxi Province, China. Among the four different treatments, two of them applied intercropped herbage treatment (Lotus comiculotus), and other two without herbage treatment. In each treatment, five trees chosen by the chessboard sampling method were used to monitor and record the population dynamics of natural predators in every 10 days. Each treatment was performed in triplicate. The natural enemies were distinguished based on their trophic relationships and taxonomy. Abundance and dominance of species, diversity indices of community were used to analyze and compare the successions of natural enemies in the four different treatments.
Compared with conventional management jujube field intercropped with herbage, integrated pest management jujube field without herbage, and conventional management jujube field without herbage, we found that the species of natural enemies of Ancylis sativa in the jujube plantations intercropped with herbage and applied IPM increased by 37.2%, 84.4% and 118.5%, respectively; and the individual number of natural enemies of Ancylis sativa by 39.2%, 91.0% and 1874%, respectively. Parasitic ratio of the larvae and pupa of Ancylis sativa increased by 46.94% and 31.27%, 3521% and 21.99%, and 116.42% and 60.33% respectively. Abundances of lacewings and parasite natural enemies of Ancylis sativa in the jujube plantations under the integrated pest management were significantly larger than the chemically controlled jujube plantations (P<0.05). On the contrary, the abundances of spiders and ladybirds were significantly smaller than their respective counterparts (P<0.05). Also in the jujube plantation with the herbage treatment, predatory bugs and other predators were significantly larger (P<0.05) than those in without intercropped herbage.
The velocity of comeback and rebuild of natural enemies of Ancylis sativa in the jujube plantations with intercropped herbage enhanced by 50%-81% compared with those in without intercropped herbage. Standard error of diversity in the jujube plantations with intercropped herbage was significantly smaller than its counterpart (P<0.05). Further statistical analysis revealed a close correlation (P<0.01) of the dynamic changes of the dominance, diversity and evenness between functional groups of natural enemies and species in the investigated jujube plantation.