9 March 2001

Take-all seed treatment can rescue wheat yields

By Andrew Blake

A NEW take-all seed treatment looks as though it can retrieve about half the yield lost between first and second wheat crops, according to NIAB trials sponsored by Monsanto.

The firm hopes to have UK approval for silthiofam, in time for next autumns cereal sowing. It is already sold as Latitude in Eire.

Last years NIAB work confirmed that some varieties perform better than others as second wheats. There were also signs that they varied in their response to the treatment, says pathologist Rosemary Bayles. In trials on second or third wheats at four sites the new treatment boosted yields by 0.36-2.35t/ha (0.14-0.95t/acre) depending on take-all severity. That represents a yield response of 3.5-42%.

In Devon, which saw the greatest response, the disease came in early and was severe. "It was remarkable that the treated crop looked normal, whereas the untreated plots were thin and stunted," says Dr Bayles.

Comprehensive fungicide programmes ruled out the effects of foliar diseases and eyespot.

Silthiofam clearly does not provide 100% control of take-all or restore yields to first wheat level, says Dr Bayles.

Comparisons with the way varieties performed as first wheats in 1996-2000 Recommended List trials suggest the average yield recovery of 1.06t/ha (0.43t/acre) represents about half of the expected loss in second wheat situations.

Varieties which yield well as first wheats tended to be among the highest yielders in the second wheat trials. But there were exceptions.

The relative performance of Consort, Soissons and newcomer Tanker seemed largely unaffected by which slot they occupied. But certain others did substantially better or worse than might have been predicted from their roles as first wheats (see table).

"We can clearly identify varieties which suffer more as second wheats," says Dr Bayles. "But they do not invariably give the best responses to silthiofam. Thats because there will be factors other than take-all at work. Its a very complex area. &#42

SILTHIOFAM TRIALS

&#8226 About half take-all loss recovered.

&#8226 Signs of varietal interaction.

&#8226 Better second wheats highlighted.

&#8226 More interaction work needed.

Variety performance as second wheat

Better than expected: Aardvark, Charger, Cockpit, Deben, Napier.

Worse than expected: Claire, Equinox, Hereward, Malacca, Oxbow, Shamrock.