Natural enemies associated with the cabbage whitefly Aleyrodes proletella in Germany

Aleyrodes proletella Linnaeus (Hemiptera: Aleyrodidae) causes severe economic damage on cabbage crops especially in organic vegetable production. Cabbage producers lack efficient and sustainable control measures against this major pest. Knowledge on the regional diversity of its natural enemies is required for the development of biological and integrated strategies to regulate A. proletella populations. Therefore, a 3-year survey of the natural enemies of A. proletella was conducted at five locations across Germany. For this purpose, parasitoids and predators were sampled from organic Brussels sprouts fields that were highly infested with A. proletella. Encarsia tricolor Förster (Hymenoptera: Aphelinidae) was the dominant parasitoid species and comprised 99.5% of all parasitoids encountered. Other parasitoids were Encarsia inaron Walker (Hymenoptera: Aphelinidae) and Euderomphale chelidonii Erdös (Hymenoptera: Eulophidae). Most sampled predators were hoverfly larvae (49.6%) followed by spiders (33.8%), ladybeetles (14.2%), predatory bugs (1.6%) and lacewing larvae (0.8%). Harmonia (Coleoptera: Coccinellidae), Sphaerophoria, Episyrphus (Diptera: Syrphidae) and Tetragnatha (Araneae: Tetragnathidae) were the most abundant genera of predators. The only whitefly specialist among the predators was Clitostethus arcuatus Rossi (Coleoptera: Coccinellidae). A detailed list of identified natural enemies is provided, and their relevance in naturally regulating A. proletella populations discussed and possible implementations in pest management strategies are proposed.