Delayed spray may cost more

4 December 1998

Delayed spray may cost more

DO not put the sprayer away because it is December – that is the advice to cereal growers with fields untreated for blackgrass.

Intentionally leaving control until spring could cost more in the long run. So every chance to spray should be grabbed, albeit with proper care to prevent herbicides, particularly ipu, getting into water, say specialists.

AICC chairman, Peter Taylor, estimates about 80% of potentially treatable crops in Suffolk have been sprayed. But colleague Geoff Dawes reckons less than one-third have been covered in his heavyland Oxon area which harbours plenty of hard-to-control and resistant blackgrass.

Mr Hawess advice to give priority to fields with the most advanced blackgrass is echoed elsewhere. Where planned Avadex (triallate) did not go on some plants already have six tillers, he notes. "Concen-trate on early sowings. Leave bigger blackgrass until the spring at your peril – there is a real chance you will struggle to get 70% control."

Most chalkland crops are sprayed up, says Bob Mills of Beds-based Banks Agriculture. "But on real blackgrass land probably only one-third is done. Unfortunately it is those that are least likely to travel.

"If you have well tillered blackgrass in wheat you ought to think about full rate Hawk or maybe 2 litres/ha with ipu. The opportunities for 1.75 litres are probably over." The main alternative, especially on fields with known target-site resistance, is Lexus DF (carfentrazone) alone or as a tank mix with 2 litres/ha of either trifluralin or pendimethalin to give a more robust approach, says Mr Mills. "But again I do not think there is much room for manoeuvre on the rate which should be 20g."

Barley, with fewer blackgrass herbicide options, merits treatment as soon as possible, he adds. &#42


&#8226 Do not give up in December.

&#8226 Still plenty of options.

&#8226 Spring approach costlier.

&#8226 Beware contact run-off.

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