Impact of the Egg Parasitoid, Anaphes sordidatus (Hymenoptera: Mymaridae), on the Carrot Weevil (Coleoptera: Curculionidae)

Abstract

Objectives of the study were to evaluate impact of the egg parasitoid, Anaphes sordidatus (Girault), on its host, the carrot weevil, Listronotus oregonensis (LeConte), in the field. Mortality of carrot weevil larvae, in the absence of parasitism, was found to be density-dependent, with an average of 1–2 eggs surviving per carrot plant, regardless of initial egg density. Larval density averaged 1.5 per infested plant over the season. A. sordidatus adults emerged from 22.3% of eggs collected (maximum 49.3% on 1 August). There was no significant correlation between percentage of parasitism and egg density or plant growth characteristics. Since density-dependent mortality occurred in the absence of parasitism, the concept of effective parasitism (reduction in damage or larval survival) was developed to predict the overall effect of A. sordidatus on the carrot weevil.