The soil food web represents the interactions between organisms of different feeding groups. Evidence suggests that soils with long and complex food webs, with more trophic links and more abundant predatory fauna, can effectively suppress plant pathogenic organisms.
We propose to test this hypothesis for the damaging root pests Delia radicum (cabbage root fly, CabRF) at two, established field trials, with ancillary studies on carrot root fly (CarRF, Chamaepsila rosae) and club root disease (Plasmodiophora brassicae). The primary site is used for horticultural crops (carrot, onion, broccoli) and incorporates a fully factorial design of organic and conventional soil treatment with organic and conventional pest management. The secondary site has replicated plots of low and high input arable production. At both sites the soil food web will be quantified over an initial two year period and key soil parameters related to soil organic matter, nutrients and the microbial biomass also determined. The abundance of entomopathogenic fungi, nematodes and beetle larvae will be specifically monitored. The primary site will also be used for field evaluation of CabRF and CarRF abundance and damage. Detailed laboratory experiments will then determine the effects of soil food web complexity on CabRF and club root, growth and development in soils taken from both field sites. Further experimentation and sampling will be for the student to develop as part of their training. Communication of the results and implications to growers and the industry will be an important part of this project.