As all soil disinfection methods tend to be harsh on the soil and costly, they should only be carried out when pathogen levels are sufficiently high to justify their use. LINK/HDC project CP 6 aimed to develop a method of measuring when the level of pathogens in the soil had reached such a level that losses to disease would be greater than the cost of treatment. The project also investigated the potential benefits of supplementing disinfested soil with compost preparations.
New DNA-based diagnostic methods were developed for quantifying soil-borne strawberry disease Verticillium wilt. Thirteen naturally infested soil samples were tested and compared with current detection. The new molecular techniques offered more accurate detection and were faster and more efficient.
When soil is disinfested, including being steamed, it is likely that beneficial soil microorganisms will be killed as well as pathogens, pests and weeds. Three types of composted material (cattle manure and waste straw, household wastes and a mixture of green waste and cattle manure) were added to steamed soil.
All composts showed a degree of suppressive activity towards Pythium ultimum, but cattle manure-based composts were the most suppressive. No composts showed activity against Fat hen weed seeds, nematode (PCN cysts) or Sclerotinia. Results showed that compost addition after steaming is beneficial, improving soil structure and adding micro-organisms.