9 July 1999

Early drill and low seed rate poses a herbicide dilemma

Management messages

aplenty were to the fore at

national distributor Profarmas

trials site open days near

Biggleswade last month. Louise Impey profiles three

key messages on autumn

herbicides, hybrid wheat and

strob/nitrogen interactions

GROWERS who opt for early drilling at low seed rates this autumn will face a dilemma when it comes to herbicide choice, warns Profarmas technical manager, Craig Morgan.

"It is very difficult to keep on top of blackgrass in this situation," he advises. "The combination of early weed germination with the lack of crop competition gives blackgrass the best possible start."

Mr Morgan believes it is no coincidence that growers have been reporting more blackgrass this season. "Many of them have already started to drill earlier, but they are still relying on contact-acting herbicides for grass weed control. They must realise that they need a residual component for good control in these conditions."

He suggests that pre-emergence spraying will be needed on blackgrass land where conditions allow. "If it is too wet, then growers must use a residual with the contact-acting herbicide. Best results this year were seen with a Hawk/Lexus mix."

Broad-leaved weed control will also need to be approached differently, he says. "The DFF dose response curve was done for crops sown at 350 seeds a sq m. Now that growers are using 150/sq m they will see more weeds coming through. Polygonums are a good example."

He concludes by reminding growers to get updated advice on product choice, timing and dose rate where they are changing the way they grow the crop. "And do not worry too much about spending a bit more on weed control. The costs are nothing compared to the yield penalty blackgrass can cause."

AUTUMN HERBICIDES

&#8226 Earlier drilling and lower seed rates demand herbicide rethink.

&#8226 Faster emerging grassweeds and blws.

&#8226 Less competitive crop.

&#8226 Include residual element with herbicide sprays.