The attractiveness of wild cruciferous plants on the key parasitoids of Meligethes aeneus


Abstract: Parasitoids can play an essential role in the natural control of oilseed rape pest populations. The host-seeking mechanism of parasitoids is based on chemical cues released by the infested host plants as well as those produced by the host insects of parasitoids. In addition, plant structure and architecture can affect the host finding success of parasitoids. A small scale field experiment was conducted to investigate pollen beetle (Meligethes aeneus Fab.) parasitism rate by larval endoparasitoids on different wild cruciferous plants: Brassica nigra (L.) W. D. J. Koch (black mustard), Raphanus sativus L. var. oleiformis Pers. (oilseed radish) and Eruca sativa Mill. (wild rocket) compared to spring oilseed rape (Brassica napus ssp. oleifera L.). In total four species of M. aeneus larval parasitoids were found: Diospilus capito, Tersilochus heterocerus, Phradis morionellus and one unidentified. Species composition of parasitoids differed with plant species. All four species were found on B. napus (P. morionellus 47%, D. capito 39.8%, T. heterocerus 8.4%, unidentified 4.8%), three on B. nigra (T. heterocerus 68.6%, P. morionellus 16.3%, D. capito 15.1%) and E. sativa (P. morionellus 44.4%, D. capito 33.3%, unidentified 22.2%) and two species parasitized larvae on R. sativus (D. capito 71.4%, P. morionellus 28.6%).The most common larval endoparasitoid species of M. aeneus in northern and central Europe are P. interstitialis, P. morionellus and T. heterocerus. Brassica nigra was the most suitable for T. heterocerus, the key parasitoid in most European countries. Similarly to Finland, in Estonia the most important parasitoid species in oilseed rape was D. capito, which was the dominant species on R. sativum and B. napus.In conclusion, we can assume, that using B. nigra in seed mixtures at oilseed rape field edges may enhance species richness and abundance of parasitoids of M. aeneus; by preserving more species of economically important natural enemies of oilseed rape pests, it is possible to decrease chemical input and apply and uphold more sustainable pest control tactics.

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