Flag leaf spray timings must be right

By Charles Abel

FAST-GROWING wheats could catch cereal growers out this season, warn agronomists.

Although some crops have only just received T1 sprays, flag leaf spraying must be applied on time.

“After the difficult conditions in April, many growers have only just applied their first sprays, and may be reluctant to go back.

“But flag leaves are starting to emerge and disease remains a threat,” says ADAS head of arable consulting Julian Hayes.

That could be a particular concern where corners were cut with T1 sprays, he advises.

“Anybody using older chemistry or recommendations written some time ago could have failed to achieve full protection of the crop.”

Growers now face the prospect of a rapid return to protect emerging flag leaves. Soissons had flag leaves showing last weekend and early-September drilled crops are close behind, he notes.

“In many cases crops had final leaf three and even final leaf two emerged when late T1 sprays went on,” says Mr Hayes. “More astute growers upped triazole rates to get more kick-back to keep those clean. Anyone who has used a strobilurin-only programme could have a problem.”

In East Anglia many crops appear to be little further forward than GS32, but leaf production is running well ahead of nodal development, says Colin Myram of Suffolk-based CropCare.

He urges growers to ignore the traditional four week gap between T1 and T2 sprays and to be prepared to go back as soon as the crop needs protection.

Many growers waited for GS32 to apply their first spray and after last weeks wind and rain have now missed T1 altogether, notes Dick Neale for Wisbech-based distributor Hutchinsons.

With flag leaves starting to emerge, he says forget earlier recommendations and apply a robust flag leaf treatment instead.

If a strob is being used, stay above three-quarters rate, and add at least a half rate of appropriate triazole, he urges. The only further spray then needed may be a “sniff” at ear emergence.

Where a T1 spray did go on flag leaf spraying can be delayed until full emergence, provided a robust triazole rate was used, he notes “But dont wait until ear emergence – thats just too long this season.”