Barclay Crop Protection

Unsettled outlook raises cleavers concern

The success of autumn herbicide programmes should not be taken as a guarantee that crops will now remain weed-free, Barclay Crop Protection has warned growers - with cleavers being a particular worry.

Grass-weed programmes have been extremely productive this year, with most growers reporting clean crops, while broad-leaved weeds have hardly been an issue thanks largely to the ongoing dry spring. But recent rain, and the unsettled, uncertain forecast for the next fortnight, has raised concerns that broad-leaved weeds could take advantage of waning residual herbicides and produce a late flush. Cleavers in particular could pose a threat both to yield and to ease of harvesting later in the year.

"In a normal year we probably wouldn't be concerned about cleaver development this late in the crop," says the company's UK sales manager Paul Haynes. "Crops should be closing over by now, but canopies are still very open at the moment.

"Not all areas of the country have been blessed with rain in recent days," Paul points out, "but where reasonable amounts have fallen, this might have been enough to start a late flush of broad-leaved weeds."

Cleavers are reckoned by many to be amongst the most damaging of broad-leaved arable weeds, with trials showing yield losses of up to 20% following heavy infestations. However, this year's late flush is less likely to affect yield loss directly; instead, if left untreated, it's harvest and drying operations that could suffer. Cleavers can slow dramatically the combine's progress through the crop and because the plant usually senesces later than cereals, cleaver seeds that make it through the combine can also have a marked effect on grain moisture content.

"Treatment may not be necessary," Mr Haynes reassures growers. "But if you decide to treat, make a careful product choice. Many crops are stressed at the moment and could become overstressed if a slightly 'hot' product is applied.

"Fluroxypyr, as in Hurler, would be a safe choice in the current conditions, as fluroxypyr is known for its 'kindness' to crops."