Agriculture Reference
In-Depth Information
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Sound rotational practice can have an important part to play in the control of
soilborne diseases and the high priority given to it in ICM systems is certainly
justified. It does not, of course, provide a complete answer to such diseases -
especially where the pathogen can be introduced from surrounding areas by
means of airborne spores. It must, moreover, be linked with effective weed
control. In an ICM system, mechanical methods may form the basis of the weed
control programme but the development of certain infestations (e.g. of couch
grass) may necessitate the use of a herbicide to reduce build up of take-all in
wheat. In the warmer regions of the world, solarization can provide a very
effective and environmentally acceptable method of reducing the inoculum of
soilborne pathogens of horticultural crops.
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Phoma canker and eyespot illustrate the need for a sound understanding of the
biology of crop protection problems in ICM. A tactic designed to reduce
inoculum levels (such as ploughing) can be counter-productive if it increases
susceptibility to the disease (as in eyespot) or exacerbates another crop
protection problem (sclerotinia stem rot). Disease control strategies which
integrate rotation and cultivations can make a substantial contribution to the
success of disease control.
•
Sound hygiene practices to reduce debris-borne inoculum in individual fields can
be of value in ICM but are likely to be less effective if inoculum is also present
in the surrounding area.
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Effective hygiene will reduce inoculum and may delay the onset of an epidemic.
However, abundant production of airborne spores provides the potential for
small amounts of inoculum to cause significant crop damage if weather condi-
tions are favourable to individual diseases at key stages during the growing
season.
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Avoiding excess nitrogen application is likely to restrict disease development
and reduce waste.
•
Biological control offers considerable potential in sustainable systems. The intro-
duction of specific biological control agents is likely to be of limited application.
Manipulation of the substrate to favour naturally occurring pathogen antagonists
offers a better prospect. At present, attempts to control diseases by introducing
specific BCAs have met with little success in agriculture but successes in both
horticulture and forestry suggest that further research in this area is fully
justified. The potential will only be achieved by understanding the ecological
interactions between pathogens and antagonists.
•
Genetic resistance offers the best prospect for non-chemical disease control. It is
essential that we maintain the broadest possible base of genetic resistance in
crops. Advances in gene technology provide the prospect of durable crop resis-
tance to disease by importing external resistance sources.
ACKNOWLEDGEMENT
We are indebted to Bill Clark, ADAS Boxworth for helpful comment.
