假眼小绿叶蝉卵的寄生蜂种类及种群动态

通过田间采梢、室内镜下查卵和饲养观察,初步获得假眼小绿叶蝉Empoasca vitis Gthe卵寄生蜂2种,分别隶属于三棒缨小蜂属Stethynium sp.和裂骨缨小蜂属Schizophragma sp.,其中三棒缨小蜂属Stethyniumsp.是优势种。2种缨小蜂的寄生动态调查结果显示,除8月和12月寄生率较低外,其它月份的自然寄生率都在30%以上,特别是10~11月寄生率最高达65%,对小绿叶蝉的虫口数量具有重要控制作用,值得进一步研究和保护利用。     

Influence of grapevine cultivars on the leafhopper <Emphasis Type="Italic">Empoasca vitis</Emphasis> and its egg parasitoids

The leafhopper Empoasca vitis (Göthe) (Homoptera: Cicadellidae) can cause economic damage in European vineyards. Egg parasitoids, in particular Anagrus atomus (Linnaeus) (Hymenoptera: Mymaridae), are the most important natural enemies of the leafhopper. In four different years, leaves of ten grapevine cultivars, which were grown in a vineyard of north-eastern Italy, were collected at the end of the leafhopper 2nd generation to determine the total number of E. vitis eggs per leaf and the percentage of the E. vitis eggs parasitized. These data were analysed for correlation with leaf density and foliar pubescence. The E. vitis eggs per leaf and the percentage of eggs parasitized by Anagrus spp. were significantly influenced by the cultivar. The number of E. vitis eggs per leaf was positively correlated to leaf density, but it was not influenced by leaf hair density. The parasitization rate by Anagrus spp. was affected by foliar pubescence, especially by erect hairs on the veins. These findings could be used for integrated pest management. In particular, (1) the more susceptible cultivars can be used as early indicators of leafhopper infestation, (2) agronomic practices, that reduce leaf density, could decrease the E. vitis population level and (3) clones with glabrous leaves would favour egg parasitoid activity.     

Searching and Oviposition Behavior of Anagrus atomus L. (Hymenoptera: Mymaridae) on Four Host Plants of Its Host, the Green Leafhopper Empoasca decipiens Paoli (Homoptera: Cicadellidae)

Anagrus atomus L. is an important egg parasitoid of the green leafhopper Empoasca decipiens Paoli. In this study the ability of the parasitoid to locate and parasitize its host was investigated on four host plants, i.e., broad beans (Vicia faba L.), sweet pepper (Capsicum annuum L.), cucumber (Cucumis sativus L.), and French beans (Phaseolus vulgaris L.). For each plant species, the behavior of the parasitoid was observed on E. decipiens infested and noninfested plants. Searching and oviposition behavior were characterized by drumming, probing, and resting. Parasitoids spent significantly less time on non-infested than infested plants, 274.5 and 875.7 s, respectively, and no probing behavior was observed on non-infested plants. Frequency of resting behavior was significantly greater on non-infested than on infested plants. Total foraging time was significantly longer on infested than on non-infested plants, indicating that A. atomus females can efficiently discriminate between leaves with and without infestation. Parasitism of A. atomus was influenced by parasitoid density, with the highest parasitism rate (64.0%) obtained at a density of 10 A. atomus females/0.1356 m² but the number of parasitized eggs per female and the searching efficiency decreased with increasing parasitoid density.