Insect pests on winter oilseed rape studied by different catching methods
¹Department of Plant Protection, Estonian Agricultural University, Kreutzwaldi 64, 51014 Tartu, Estonia; e-mail: email@example.com
²Department of Field Crop Husbandry, Estonian Agricultural University, Kreutzwaldi 64, 51014 Tartu, Estonia
The distribution, species association and number of pest insects on winter oilseed rape of varieties ‘Wotan’ and ‘Express’ were studied in field experiments. Three catching methods were used: black plastic basins on the soil surface between plants, yellow flight traps filled with water at the height of the crop canopy and the shaking of plants above a plastic basin. The most abundant pest species was the pollen beetle,Meligethes aeneus, while the number of individuals from the species M. virescens in traps was much lesser. The other important group of pest insects were weevils Ceutorrhynchus spp., the most common of which was the cabbage seed weevil, C. assimilis. Three species of flea beetlesPhyllotreta undulata, Ph. vittata and Ph. nemorum were typical contents of traps during May. In the last decade of May, there was a large number of thrips (Thysanoptera, Tripidae) in traps.
Winter oilseed rape began to flower to some extent later, when pest insects of cruciferous plants had ended their hibernation. Therefore, the pests first inhabited weeds and already flowering plants, from where they later moved onto winter oilseed rape.
In the field of winter oil seed rape, chemical pest control with a pyrethroid, Fastac, did not significantly influence the abundance of pest insects. In the last decade of May, the total number of beetles in all test variants was relatively small, but, at the beginning of June, it increased almost to an equal extent. On the basis of flight traps, heavy damage of pods could be assumed, however, only a few larvae fell into traps on the soil surface, and virtually no damaged pods were detected. Thus the spraying with Fastac had no significant effects on the number of insects caught in traps.