Wheat growers seeing big surges in blackgrass emergence are being advised to carefully assess crops before ripping them up and redrilling.

As a result of the summer’s prolonged drought, some early drilled winter wheats are facing a heightened weed burden.

This is after the dry conditions prevented pre-emergence herbicides from working effectively, says Mike Thornton, head of crop production for agronomy firm ProCam.

See also: Crop Watch: Beet moth problems and blackgrass flushes

“Despite being a distant memory, the summer’s dry and hot conditions are still having an effect on the new cycle of cereal crops,” Mr Thornton explains.

“Some wheats which were drilled ahead of schedule or on lighter land have suffered from a lack of soil moisture, which has prevented soil-acting pre-emergence herbicides from working to the best of their ability.”

As a result, some winter cereals are currently facing heightened competition from out-of-control weeds which, in the most severe cases, could threaten the crop’s viability and profitability.

Mr Thornton recommends that each field should be assessed on a case-by-case basis to decide if the current crop, or part of it, should be sprayed off and redrilled.

This could be either with a replacement winter crop or with a subsequent spring crop.

Where the weed burden is excessive or contains difficult-to-control competitors, such as blackgrass, ryegrass and brome, it could be quite an easy decision to make, he says.

For example, if grassweeds have made it to the two-leaf stage or beyond, they will be very difficult to control as most contact herbicides have been rendered ineffective by mounting resistance.

Admit defeat

“In the most severe cases, it will make sense to admit defeat sooner rather than later and to write-off the current crop so that weeds can be burned off ahead of a replacement crop being established.”

For many growers, Mr Thornton says it’s still not too late to get a replacement winter crop into the ground. For others, deferring to a spring-sown cropping strategy might be the better option.

“In both cases, growers should be aware of the restrictions imposed by certain active ingredients on replacement crops.”