The literature on the relation of uncultivated land to crop pests is reviewed with a distinction between biological and physical relations. A description of preliminary experiments demonstrating types of relationship suitable for quantitative work is followed by an account of the techniques used in a two year study of Cabbage Aphid (Brevicoryne brassicae L.) infestation of cultivated crucifers. The progress of this infestation in both seasons is traced on a basis of the aphid's life history, and the factors affecting the aphid populations are discussed. Nutritional factors are considered of major importance. The edgegrowch is assessed as a parasite and predator reservoir and, in the crop, the edges and centre of the field are compared in respect of edgegrowth effects. Physical effects of shelter on the growth of the host plant and the adverse effects on the aphid's reproductive rate are discussed; also the deposition of aphids from air currents. Heavy predation at the open edges is considered due partly to the invasion of predators from the edgegrowth and partly to heavier oviposition by Syrphidae near flowers which provide food for the adult females. Conclusions are given on the general role of uncultivated land in a pest infestation of a crop, with particular reference to the pest species studied and the strips of edgegrowth immediate to the crop.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:602135 |
| Date | January 1962 |
| Creators | Van Emden, Helmut Fritz |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/13587 |
Page generated in 0.0119 seconds