New crop management guidelines designed to prevent mycotoxin contamination of grain are being published to coincide with the introduction (this July) of EU limits for deoxynivalenol (DON) and zearalenone (ZEAR) in milling wheat.

Based on previous surveys, a small proportion of the UK wheat crop may exceed the maximum DON limits of 1250ppb in unprocessed grain.

The same applies to ZEAR, produced by the same fusarium pathogens.

Its limit is just 100ppb.

A new topic sheet provides an essential update to last summer's HGCA project for anyone growing milling varieties next season, stresses Roger Williams of the HGCA, who will have copies ready to distribute at Cereals 2006.

"Growers have a responsibility to show due diligence in crop management to minimise the risk of mycotoxin contamination," he says.

"Rapid, on-farm DON testing may help where there are good reasons to believe the risk may be high."

There are several DON tests on the market with appropriate sensitivity, but each is suited to a particular use.

The easiest to use are based on a "dipstick" format test and give a yes or no answer.

More sophisticated tests offer some degree of quantitative information but may not be suited to use on farm, explains Dr Williams.

"The most suitable test will depend upon the quantity of grain you're testing, the time and facilities available, and the price tag.

Regardless of the test used, mycotoxin distribution is unlikely to be uniform within a bulk and therefore careful sampling is essential to result reliability."

There is currently no "dipstick" format test for ZEAR, but recent surveys show that in most cases if DON does not exceed the limit, then ZEAR will not.

fwarable@rbi.co.uk