Review on the possible interactions of pests, diseases & weeds in cereals grown in organic and conventional agriculture

Summary

Background
The demand for organically produced food is outstripping the ability of UK farmers to supply it and the majority is imported. Furthermore, there is a major shortfall in home-produced organic cereals and cereal products, including straw. In response to this need, the consequences of increasing the area of organically produced cereal crops on pests, diseases and weeds require evaluation. Furthermore, as the area of organic cereals increases, crops may be grown more in the major cereal production regions. This could have consequences for both the organic producer and farmers growing cereals conventionally.
Objectives
(i) review the current state of knowledge on the status and distribution of pests, diseases and weeds in organic and conventionally grown cereals,
(ii) assess the likely rate of expansion of organic cereal production and the areas where this is most likely to occur, together with any likely or consequent change in the distribution of conventionally grown cereals,
(iii) assess the distribution of specific cereal cultivars and species in organic and non-organic production in relation to their impact on disease, pest and weed distribution. A specific sub-objective will be to assess the likely impact of the increased use of organically produced seed on seed-borne diseases,
(iv) try to forecast whether or not the changes in cereal production will affect the current status and distribution of pests, diseases and weeds, and, if so, in which major directions,
(v) make recommendations for future research, both to ensure that the forecast under paragraph (iii) is correct and that any negative trends are highlighted and, if possible, dealt with.
Methods
A literature review was undertaken to identify potential risks to conventional and organic production cereals on an extension of the organic area on risks of pests, diseases and weeds.
See main report for results.
Future work
Monitoring of the more important pests and diseases in organic production would be prudent. Any problems for non-organic cereal producers are unlikely to arise for several years because of the small scale and slow increase of organic cereal production, but this should be regarded as a ‘grace’ period to allow for development of appropriate solutions before any potential problems become important in practice.
Problems for organic producers may emerge more quickly; these need to be monitored so that cultivar and other recommendations can be developed. It is likely that the best spectrum of cultivars for non-organic and organic production will differ, which would help in restricting disease interactions between the two production systems. Any constraints on production of seed for organic cereal growing should be removed so far as possible.
Development of the system of bi-cropping, both for organic and non-organic production, should be continued since there are good indications that this can restrict problems due to slugs, aphids and BYDV, septoria leaf and glume blotch, and probably take all.
The importance of using disease resistant cultivars needs to be still further stressed for both organic and non-organic production. The influence of sowing date on disease development, particularly in the autumn, needs more attention. Renewed efforts to develop and introduce production of cultivar mixtures, particularly for organic cereal production, would help to restrict disease development.
Fundamental studies on the biology of the major perennial weeds are still needed. Although seed spread can be minimised by frequent cutting, the effects of this on the spread of roots and rhizomes is poorly understood.
It is important to maintain a regular watch or survey for indications of any increase in the key seed-borne diseases that may occur in organic cereal production and to determine the reasons for any such increase.
Technology transfer
The report will be suitable for wider dissemination among researchers and the agriculture industry. All contributing organisations have means by which this information can be made available through press briefings, Web-sites and at farming events.