Establishing biofumigation as a sustainable pesticide replacement for control of soil-borne pests and pathogens in potato and horticultural crops.

Our research is designed to help UK farmers control soil pests which damage crop production cheaply and effectively at the same time as reducing dependence on conventional pesticides which might harm the environment. The most damaging of these soil pests are microscopic nematode worms. There are different species of nematodes: some attack potato plants whilst others can infect a range of plants, including carrots and soft fruit. The most prevalent economically important species of nematode, and so the one that has the highest economic impact on UK farmers, infects the roots of potato plants and is consequently termed potato cyst nematode (PCN). There are disproportional impacts on our potato industry because of a higher incidence of PCN in the UK than in most of Europe. EU legislation has resulted in the recent loss of two major chemicals used to control nematode pests, termed nematicides, in response to the environmental concerns their use raised and plans to amend the legislation regulating pesticide use still further are likely to remove the three remaining nematicides, possibly quite suddenly. This is causing major concern to the British potato industry because it is doubtful if new pesticides, which are effective but also meet appropriate environmental safety standards, can be developed in time to replace the pesticides being phased out. One alternative control method that could be adopted in the limited timeframe available to UK potato growers is a strategy known as biofumigation, which suppresses pests by incorporating mustards and other types of plants into soil. Potato Council Ltd (which safeguards the interests of the UK potato growing industry) and the Horticultural Development Company (which promotes the UK horticultural sector), in conjunction with potato businesses, have now committed to support research to understand exactly how biofumigation works and how the potential of this technique can be exploited most effectively under field conditions. Our preliminary work has characterised a number of different plant species that produce natural chemicals which detrimentally affect PCN. We have shown that biofumigation can be used to stop the eggs of PCN from hatching into worms which subsequently attack potato plants. We have identified different types of mustard plant that could be used in biofumigation because of the range of natural anti-nematode chemicals they produce. However, inconsistencies in the effectiveness of these plants and a lack of detailed data on how best to deploy biofumigation under a range of agronomic situations prevent the widespread uptake of this sustainable pest control technique. This project will address this knowledge gap by elucidating the fundamental biochemical and metabolic processes underpinning effective biofumigation. It will characterise the profiles of the active chemical compounds, called glucosinolates, of different biofumigant mustards and determine how these vary with plant development stage and environmental factors. It will identify novel active compounds potentially effective against pests but not, as yet, evaluated in biofumigant field trials. We will analyse the effects of biofumigant plants on a range of pests both in glasshouse studies and in multiple field trials. We will use a novel plant growth technique that makes soil appear transparent allowing us to observe the effects of biofumigation on some of the nematode species for the first time. It must be shown that biofumigation does not adversely affect UK soils before the approach can be endorsed by the Potato Council, DEFRA, EU or certifiers of organic produce. We will therefore analyse the impact of biofumigant crops on beneficial organisms in the soil when deployed in the field. Outputs of the research will allow optimal deployment of biofumigation strategies for maximum efficiency over a range of field conditions, providing a sustainable pest control option for both conventional and organic farmers.