Studies On The Bionomics Of Small Green Leafhopper And Its Egg Parasitoids

The small green leafhopper (SGL), Empoasca vitis (Gothe), is one of major tea pests, which has caused severe damage in south of China. The mymarids are dominant egg parasitoids of the leafhopper in Fujian tea plantations.Studies on the small green leafhopper and its egg parasitoids in 4 tea varieties (Fuyun no.6, Fudingdabaicha, Huangdan and Tieguanyin) were conducted at tea plantations of Fujian Agriculture and Forestry University (FAFU), and Fuan from May, 2006 to November 2007. By plant-flapping, pickting shoots, dissecting the leafhopper's eggs from the tea shoots under microscope and rearing the parasitized eggs in laboratory, the population dynamic, the eggs density of the leafhopper and the egg parasitism were observed. The bionomics of the parsitoids were preliminary studied for the first time. The results were as follows:By using five-point type, random-type and parallel-type sampling tea shoots to compare the egg density of the SGL, it revealed that there was no obvious distinction among the 3 sampling methods, which can be used for studying the egg density of the SGL.The small green leafhoppers preferred to lay their eggs in younger shoots. The eggs density of the SGL were significantly different within the different shoot positions, which within 1^st to 4^th leaves were more than that within 5^th to 7^th leaves.From the correlation analysis among the population dynamics of the eggs, nymphae and adults of the SGL in 4 tea varieties, a significant positive correlation was shown. Which indicated that the population dynamics of the SGL were generally similar among the 4 tea varieties.The population density of the SGL had two peaks annually and the first peak was higher than the second one. The egg parasitism were basically consistent within the 4 tea varieties investigated. The egg parasitism were highest in the winter and lowest on April, which varied with the eggs density of SGL on tea plants, expect during the cold season.Investigations at 3 different tea plantations in Fuan revealed that the eggs density coincided generally and with significant seasonal responses. The eggs density were significantly different among the 3 tea plantations, which was the lowest at Tianxiang tea plantation and the highest at Beimen tea plantation. The egg parasitism were not significantly different among the 3 tea plantations. The average of the egg parasitism were, the highest (70.46%) at Tianxiang tea plantation and the lowest (60.57%) at Xibing tea plantation.By dissecting of the leafhopper's eggs from tea shoots and rearing the parasitized eggs in the laboratory, 2 species (Schizophragma sp. and Stethynium sp.) in 2 genera of Mymaridae had been found. Adult activity, longevity and oviposition of the parasitoids were significantly affected by temperature and light. The parasitoids can reproduce in both ways of amphigony and arrhenotoky. Under 25℃condition, the lifecycle from egg to adult emergence lasted for about 21.40 days. After 10% honey water solution was supplied as supplementary nutrition, the female longevity could be prolonged significantly. The longevity was negatively in correlated with temperature. The average reproductive capacity in Schizophragma sp. (about 36.83 eggs per female) was much more than that in Stethynium sp. (about 22.33 eggs per female).