THE last serious aphid attack on arable crops came in the spring of 1995. The pest arrived early and warm weather encouraged a rapid build-up. Natural aphid predators couldnt cope alone, so most crops were sprayed with an aphicide.
Since then, colder winters and higher numbers of natural enemies have kept aphid levels low. But it takes only two weeks of favourable weather to cause an epidemic, and this season has begun milder than usual, giving autumn populations of the pest a good start.
If natural predators also had a good start, particularly in the spring, they could reduce the need for aphicides as is the case in glasshouses. That is the thinking behind a LINK-funded project at IACR-Rothamsted, due to finish this autumn. It is investigating ways to manipulate predatory parasitic wasp populations to increase their usefulness in the biological control of aphids.
Offering them suitable habitats near the crop and using laboratory-produced aphid sex pheromones to draw them in has proved successful in increasing aphid mortality in pot trials. But further studies are needed to ascertain which habitats are best, and whether attracting parasitic wasps to the crop works in practice.
Nevertheless it opens up the possibilities of using an integrated, push-pull approach to controlling aphids, using pheromones in conjunction with aphid repellents and antifeedants on the crop.