Impact of overwintering refugia of Anagrus atomus (Hym.: Mymaridae) on egg parasitism of grape leafhopper Arboridia kermanshah (Hem.: Cicadellidae)

Anagrus atomus (L.) (Hymenoptera: Mymaridae) is an egg parasitoid and an important mortality factor for the grape leafhopper, Arboridia kermanshah Dlabola (Hemiptera: Cicadellidae) populations in Isfahan vineyards. A study was conducted to characterize the plants in which A. atomus overwinters, dispersal of the parasitoid, and the level of parasitism of grape leafhopper eggs in two vineyards through 2000-2001. A. atomus overwinters in leafhopper eggs on rose, sweetbriar and blackberry. In a vineyard, with nearby overwintering refuges, the parasitoid emerged by mid-March from alternate hosts. It completed one generation on these alternate hosts, and then arrived in vineyard by late April, synchronized with grape leafhopper oviposition. The pattern of wasp colonization and parasitism indicated that parasitoids were more abundant in the vineyard with refuges close to it. In early spring, density of A. atomus was more than twice in this vineyard compared with vineyard with no refuges close to it. By mid season (July), A. atomus parasitism of A. kermanshah was significantly greater in the vineyard associated with refuges. Cumulative egg parasitism demonstrated that enhanced early season parasitism resulted in a better season-long increase in the mortality imposed by A. atomus on A. kermanshah eggs.