Impact of Soil Tillage on Parasitoids of Oilseed Rape Pests

Some of the parasitoids of important oilseed rape pests over-winter in the soil within the pupal chambers prepared by the host larva. Thus post-harvest soil tillage can have a great impact on the survival of these insects and the parasitization of oilseed rape pests the following year. Conventionally, soil tillage following harvest of oilseed rape was usually by ploughing but, more recently, methods of reduced tillage and direct drilling have become increasingly common. Experiments have shown that ploughing almost always reduces the number of parasitoids emerging the following year by 50% or more, while other kinds of tillage have a varying but lesser effect. Reduced, non-inversion tillage can be part of an integrated strategy to control insect pests in oilseed rape.