Cabbage seed weevil (Ceutorhynchus assimilis Payk.) and its parasitoids in oilseed rape crops in Estonia
Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences,Kreutzwaldi St. 64, EE51014, Tartu, Estonia; e-mail: reelika.kevvai@emu.ee
Abstract:
Abstract: Besides pollen beetles, the cabbage seed weevil is the second most numerous crucifer-specialist in Estonian oilseed rape crops. The occurrence of cabbage seed weevil and its hymenopterous parasitoids was studied in standard and integrated cropping systems in winter and spring oilseed rape crops in 2004–2005. Cabbage seed weevil is more synchronized with winter oilseed rape and its abundance was greater in winter than in spring. The average pod damage was 9.9% in winter and only 1.2% in the spring crop. In winter oilseed rape, the population of C. assimilis was more numerous in the integrated than in the standard cropping system. Three parasitoids of seed weevil – Trichomalus perfectus, Stenomalina gracilis, Mesopolobus morys – were caught with yellow water traps but their abundance was low. The larval parasitism rate was higher in the integrated cropping system (22.2%) than in the standard cropping system (9.7%). Trichomalus perfectus was the dominant species emerging from C. assimilis larvae.
Key words:
Ceutorhynchus assimilis, cropping system, insecticide, oilseed rape, parasitoids