Field manipulation of populations of individual staphylinid species in cereals and their impact on aphid populations.

Abstract

1. Four species of staphylinids were caged separately on wheat and their effect on the population development of the grain aphid, Sitobion avenae (F.), was investigated over two seasons.
2. A novel field cage design was used to exclude all but the staphylinid species under investigation.
3. Predator effects were compared with total-exclusion cages in which all predators and parasitoids were kept out.
4. During a high-density phase of aphid population development only Philonthus cognatus (Stephens) significantly influenced aphid population numbers.
5. At low aphid densities, Tachyporus obtusus (L.), T.chrysomelinus (L.) and P.cognatus reduced aphid population levels.
6. The experiments showed that Tachyporus spp. can reduce the numbers of cereal aphids prior to the exponential phase of aphid population increase and that P. cognatus causes some reduction at both the stages of aphid population growth investigated.