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Causal organism - Gaeumannomyces graminis
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Most farmers employ cultural control of take-all by ensuring a sensible
crop rotation
. A one year break from susceptible
crops will usually prevent the disease causing problems in the subsequent
cereal crop. Early drilled crops are particularly prone to severe disease
attacks. It is therefore advisable to sow first wheat crops first, long-term
wheats next and second and third wheats last. Seedbeds should be well consolidated
and fields well drained with good soil structure, particularly in light soils.
Volunteers and grass weeds should be controlled to prevent carry-over of the
disease when non cereal crops are grown. If successive cereal crops are grown
take-all will generally build up during the second or third years. However,
take-all will almost invariably decline during subsequent years until it reaches
a stable position when yields are acceptable. The yields of long term cereals
where take-all
decline is established are never as high as those of a first wheat
but may allow the crop to continue to be grown economically. If a run of continuous
cereals is broken by a non- susceptible crop, the process of take-all decline
will be repeated in subsequent cereal crops. A set-aside break is usually
not sufficient to destroy the take-all decline position and cereals can often
be re-introduced without suffering yield loss.
Disease resistance
in wheat, barley and oats to the respective subspecies of G. graminis
is low. However, G. graminis var. avenae is not widespread in
the UK and in most areas it is possible to exploit the resistance of oats
to take-all and use the crop as a break crop in a rotation. There is some
evidence of good levels of resistance in some triticale varieties.
There are two main fungicide seed treatments available for the control of
take-all - silthiofam and fluquinconazole (Latitude and Jockey). Seed treatment
with triadimenol + fuberidazole
(Baytan) can suppress the autumn phase of the disease, which can be damaging
in early-sown crops in high risk situations. However, the use of Baytan does
not give good enough control to allow crops in very high risk situations.
Biological
control of take-all is an area of considerable interest, mainly because
of the lack of any other method of control in continuous cereals. Many biological
agents have been investigated, particularly Pseudomonas fluorescens,
which has been used as a seed treatment against take-all. Yield increases
of up to 15% have been observed in the USA using Ps. fluorescens, but
results in the UK have been much less successful. The difficulties of introducing
a single fungal or bacterial culture into the complex ecology of the soil
have not been easy to overcome. Success is likely to come with a mixture of
several micro-organisms, possibly delivered as a seed treatment.
The phenomenon of take-all decline is thought to be a type of biological control,
and numerous attempts have been made to isolate the organisms responsible
for the decline of take-all in the field. Results in the UK have not been
very successful but work on Phialophora, Ps. fluorescens and other
antagonists continues.
