26 June 2001
Amistar fungus fears unfounded
By Tom Allen-Stevens
RESEARCH suggesting some ear sprays may favour mycotoxin development has been dismissed as “giving a false picture” by a leading cereal pathologist.
The HGCA-funded trials showed that the use of Amistar (azoxystrobin) is extremely effective against the Fusarium species Microdochium nivale.
But the work, led by Dr Paul Nicholas of the John Innes Centre, found the fungicide has a negligible effect against the toxigenic species, such as Fusarium culmorum.
“So where M. nivale levels are high and azoxystrobin is applied, it allows the other Fusarium species to dominate,” said Dr Nicholas.
“This, in turn, may increase the level of mycotoxins found in the grain. So its important that growers do not rely on Amistar alone for the control of ear blight.”
But the claims were dismissed by ADAS cereal pathologist Bill Clark.
“These are very much the results youd expect from an inoculated trial, but you would be unlikely to get them in a commercial situation,” he told FWi.
In the trials, plants were inoculated with mixtures of ear blight pathogens, creating disease levels higher than those which occur naturally.
Climatic conditions were also manufactured in order to promote F. culmorum development — warm and wet during flowering.
“The mycotoxin angle is always overplayed. The level of F. culmorum found in the field does not always correlate with that found in grain,” Mr Clark added.
He believes rotation and cultivations play a much bigger role than fungicide type in promoting mycotoxin development in the field.
“Its mainly a problem in France where wheat is grown after maize, especially in a minimum tillage situation.”
An HGCA-funded survey in 1999 showed none of 320 grain samples taken from UK farms had Fusarium-related mycotoxin levels above the EU limit for grain.
Amistar is not recommended for the control of F. culmorum, and should be mixed with a triazole, especially if high levels of the species are expected.
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