The HGCA's fusarium risk assessment for wheat has been improved to allow growers to more accurately determine the likelihood of exceeding the legal mycotoxin limits in grain.

The main changes have been to include T3 fungicide choice and dose within the assessment and to enlarge the options for the cultivations section to include different types of non-inversion tillage, according to Simon Edwards of Harper Adams University College.

Four options are now available for cultivations: Direct drilling, standard non-inversion tillage, intensive non-inversion tillage and ploughing. Crop debris is an important source of fusarium, he explains on a newly-updated HGCA topic sheet.

"Complete burial by ploughing reduces risk to the greatest extent, while direct drilling is the highest risk. Intensive non-inversion tillage (three or more cultivations with discs, tines, or chisel plough) is more effective at reducing risk than standard non-inversion tillage (one or two cultivations).

"The division of non-inversion tillage into those three categories accounts for the differential benefits of chopping and burial of crop debris during some min-till operations."

The assessment is also now ordered chronologically and split into two sections to allow growers to assess risk pre-flowering so fusarium control can be factored into T3 fungicide choice. That has been included for the first time this year, Dr Edwards says, to account for the benefit some T3 fungicides can make in reducing fusarium ear blight and mycotoxins.

"Growers can reduce their risk score by two points by using an appropriate fungicide at half to three-quarter rate, and by three points for three-quarter rate and above."

The new assessment also clarifies what is meant by high rainfall at flowering and pre-harvest.

A retrospective analysis of harvest 2007 samples showed the modifications would reduce the number of samples that the risk assessment suggested would be high risk, but, in fact were below the legal limit for DON of 1250ppb.

Performing a fusarium risk assessment is required by crop assurance schemes and became mandatory as part of the grain passport for wheat during 2007. "But it is important to remember the scheme is only a guide to risk and growers should consider having grain tested if aware of high fusarium incidence in crops," Dr Edwards stresses.

Fusarium risk assessment

• Updated risk assessment published
• New HGCA topic sheet
• Includes T3 fungicides
• Increased cultivation options
• Clarifies rainfall requirements