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.

Soil-borne pests, including nematode and fungal species, are major constraints to crop production. Nematode control in agricultural crops is expensive, often ineffective and reliant on synthetic chemicals. Many chemicals have been withdrawn, with the remaining three likely to be withdrawn gradually or abruptly due to EU legislation. Chemical control of soil-borne fungi is also problematic. New approaches that have broad efficacy and are suitable for use on a wide range of crops are urgently required. Biofumigation involves the incorporation into soil of brassicaceous plants, which produce a range of secondary metabolites, including glucosinolates, which are able to control pests. However, inconsistencies in efficacy and a lack of detailed data on optimal deployment under a range of agronomic situations prevent the effective, widespread uptake of this pest control technique. This programme will address this knowledge gap by elucidating the fundamental biochemical and metabolic processes underpinning effective biofumigation strategies. It will characterise glucosinolate profiles of different biofumigant brassicas and determine how these vary with plant development stage and environmental factors. It will identify novel secondary metabolites potentially effective against pests but not, as yet, evaluated in biofumigant field trials. The effects of biofumigant plants on a range of pests both in glasshouse studies and in multiple field trials will be determined. We will use a novel plant growth system that allows visualisation of plant-feeding nematode species for which there is little information regarding the effects of biofumigation. In addition we will evaluate the impact of biofumigation on the non-target below-ground fauna. Outputs of the research will allow optimal deployment of biofumigation strategies for maximum efficacy over a range of field conditions, providing a sustainable pest control option for both conventional and organic crop production.

A: Beneficiaries from this research
Improving the environmental sustainability of agriculture whilst increasing food production is a key aim of the Government's food security agenda; finding more environmentally acceptable methods of pest control will make an important contribution to this objective. Our research is designed to help UK farmers control key soil pests more cheaply and effectively at the same time as reducing dependence on conventional pesticides.
A1: Commercial private sector. (i) Suppliers of planting material to the UK potato industry: The Potato Council estimates the UK potato industry is worth £3 billion p.a. Our proposed research supports suppliers of inputs for potato cropping: It will provide planting material of biofumigant crops with assured efficacy to all growers at less cost than the alternative of chemical control. (ii) UK potato growers: They urgently need new, more economic approaches to control Globodera pallida. The pesticides used to control this nematode are the largest variable cost of the growers who use them and currently 23% of the UK potato acreage is treated each year. This is unsustainable given EU plans to phase out these pesticides. Our novel biofumigation approach is cheap, effective and compatible with both conventional and organic production. (iii) Supermarkets: Major supermarkets such as Waitrose, see value in removing even the theoretical risk of pesticide residues from the potatoes they sell. Our outputs will support that policy.
A2: Policy-makers. DEFRA and SEERAD must implement EU's amendment to Directive 91/414/EEC that will reduce use of crop protection chemicals in agriculture. The Directive involves the withdrawal of pesticides from the UK market, a challenge for UK potato and horticultural production unless effective alternatives for control of G. pallida and other nematode species can be adopted in the timescale that the Directive sets. For the EU, our work would support practical implementation of their policy to replace certain pesticides. DEFRA and SEERAD must also support an EU Directive specifically aimed at potato cyst nematodes (2007/33/EC).
A3: General Public. Most of the UK population consumes the crops, ranging from potatoes to soft fruit, that are attacked by nematodes and fungi so will benefit from produce that is produced in as cost-effective and environmentally sustainable way as possible..

B: Nature of benefits from this research
B1: Benefits for UK economic competitiveness. The increasing prevalence of G. pallida has contributed to a decline in the UK potato crop of 12% between 1999 and 2012. This is a larger fall than for other major EU producers that lack this pest. Our work would help overcome the problem of PCN control that faces many UK producers.
B2: Increasing the effectiveness of public services and policy. It is relevant for those who seek to implement change in policies, such as the amendment to Directive 91/414/EEC and implementation of 2007/33/EC, to have alternative practical procedures growers can adopt.
B3: Enhancing quality of life, health and creative output. Reducing the need for pesticides carries a benefit for both UK biodiversity and the consumer. A distinctive feature of this work is the short lead-in time it requires before practical benefits can be obtained. A recent Royal Society report identified a clear need for training more researchers in agricultural sciences, so the postdoctoral scientists in this project will be trained in an area of considerable importance and recent neglect.

C: Ensuring benefits from this research reach users
C1: Communication and engagement plans. This project involves the Potato Council Ltd and Horticultural Development Company. Another eight partners from across the potato and horticultural industries are also involved, which will help ensure the outputs from the project reach the end-users as described in the 'Pathways to Impact' section of this application.