The use of surrogate herbivores for the pre-release efficacy screening of biological control agents of Lepidium draba

摘要

Pre-release efficacy assessment has been suggested as a primary selection criterion for potential biological control species to insure the success and safety of biological weed control. Pre-release efficacy of candidate agents is commonly assessed byexposing insects to target plants in the garden or greenhouse (native range) or in quarantine (introduced range) before or in parallel with host-specificity testing. Conducting pre-release impact experiments for several candidate agents simultaneously may be difficult because potential agents are either scarce or may require development of novel cultur-ing procedures. We propose an alternative approach to pre-release efficacy assessment that utilizes oligophagous or polyphagous insect herbivores from the introduced range as surrogates for biological control agents to assess the impact of specific feeding niches on the target weed to direct the search for effective candidate agents. Surrogate herbivores can be cosmopolitan or indigenous insects collected directly from the invasive plant and confamilial species. Insect pest species are particularly well suited to act as surrogates because they are seasonally abundant or easily reared. Based on previous surveys, we identified surrogate herbivores attacking different above-ground plant organs of the biological control target hoary cress (Lepidium draba L., Brassicaceae). We tested the density-dependent impact of four oligophagous herbivore species on L. draba to demonstrate the applicability of this novel efficacy assessment technique. We found that the endophagous stem miner, Ceutorhynchus americanus Buchanan (Coleoptera: Curculionidae), had the highest per-capita effect on hoary cress growth, suggesting candidate agents within this niche should be prioritized.