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7 February 2007
Chemical pesticides on their way out?
Consumer concern about chemical pesticide residues on food is driving the search for
alternatives. New research suggests that biocontrol, using beneficial bacteria or fungi to control
plant disease and pests, could be developed as an effective alternative. The research focused
on developing a way of applying biocontrol agents to seeds before they are planted. This offers
an early non-chemical means of reducing or preventing the devastating effects of disease or
pest attack on crop production.
Before planting, seeds are routinely pre-treated with chemical pesticides to protect the plant against devastating
diseases and pests. However, UK researchers have now demonstrated that biocontrol agents can also be applied to
seeds during drum priming, a seed preparation method that is used commercially to improve germination. They
demonstrated, for the first time, that during the drum priming process it is possible to apply mixtures of fungi
(Clonostachys rosea IK726 or Trichoderma harzianum T22) and bacteria (Pseudomonas chlororaphis MA342 or P.
fluorescens CHA0), to carrot and onion seeds.
Biocontrol uses beneficial bacteria and fungi to help reduce the damage done to the young plant by pests and diseases.
The biocontrol agents work in number of ways to protect the plant, for example by triggering the plant’s natural defense
system to protect it from more harmful pests and diseases or by competing with pathogens for space and nutrients.
Because the bacteria and fungi are not toxic to other organisms, they pose a low risk to the environment.
Biocontrol agents applied to the seed need to be present in sufficient numbers to be effective once the seeds are
planted. All four microorganisms were found to grow on carrot seeds during the priming process. However, only bacteria
grew once applied to onion seeds during the priming process. The fungi remained alive but did not increase in numbers,
so higher initial doses of the fungi were required to reach a sufficient level for protection on onion seeds. Similarly,
different amounts of biocontrol agents were required for carrot and onion seeds to achieve the target amounts of
microbes on the seeds. These results suggest that the processes will need to be tailored to each plant species.
Microorganisms applied as biocontrol agents must also survive in the soil and on young plant roots if they are to have a
beneficial effect. The researchers found that bacteria and fungi survived on roots and in surrounding soil for up to 8
weeks and also that applying larger doses of microorganisms led to greater numbers on the roots and in the surrounding
soil.
The authors state that applying combinations of bacteria and fungi during drum priming is an important step towards
achieving a commercially viable way of delivering beneficial microorganisms to seeds and soil. Using combinations of
microorganisms may also improve the overall efficacy of biocontrol agents and ultimately could reduce dependence on
pesticide-based seed treatments.
The future development of these biocontrol agents and other “biopesticides” (any biologically based agent used for the
control of plant pests) will depend on changes to regulations, as the present system of regulation is designed for
synthetic chemical pesticides. The RELU1 project, conducted at the University of Warwick, and the work of the EU policy
action group, on the Regulation of Environmental Biocontrol Agents (REBECA)2 are addressing this issue.
1
The Rural Economy and Land Use (RELU) project aims to understand challenges faced by rural areas in the UK. See www.relu.ac.uk and
http://www2.warwick.ac.uk/fac/soc/pais/biopesticides/
2
REBECA is an EU policy support action to review possible risks of biocontrol agents, compare regulation in the EU and the USA and to
propose alternative, regulatory procedures. See: www.rebeca-net.de
Source: Bennett, A. J. and Whipps, J. M (2008). Dual application of beneficial microorganisms to seed during drum priming. Applied Soil Ecology
38 (1): 83-89
Contact: [email protected]
Themes: Agriculture, Soil
Opinions expressed in this News Alert do not necessarily reflect those of the European Commission
To cite this article/service: "Science for Environment Policy": European Commission DG Environment News Alert Service, edited by
SCU, The University of the West of England, Bristol.
European Commission DG ENV
News Alert Issue 95
February 2008
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