Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Addition of nectar sources affects a parasitoid community without improving pest suppression.

Abstract

A life-table approach was used to test the effect of adding flowering buckwheat to leek plots on mortality and estimated population growth of the invasive leek moth, Acrolepiopsis assectella. This approach was used to estimate the benefits of nectar provisioning on multiple members of the leek moth's parasitoid complex, and the impact of parasitism on the pest's predicted population growth rate. Addition of buckwheat to leek plots shifted the relative abundance of different larval and pupal parasitoid species but did not increase or decrease parasitism levels or their population-level impact on the leek moth. The life-table analysis demonstrated that parasitoids reduced the estimated population growth rate of the leek moth by up to 72%, which far exceeds similar estimates from its native range. Parasitoids found to contribute to leek moth mortality were Itoplectis conquisitor, Conura albifrons and the biological control agent Diadromus pulchellus. In addition, Gambrus ultimus, Scambus calobatus, and Habrobracon sp. are reported here developing on A. assectella for the first time. This study reinforces the hypothesis that the addition of nectar resources to agricultural systems may not have straightforward positive effects and can favour some natural enemies over others, but may not have any overall impact on pest suppression.