Hitting weeds while they are still small should be the main aim where spring blackgrass control is required, regardless of product choice, advises Nick Myers, national agronomy manage at distributor ProCam.

“The next few weeks are going to be crucial. With blackgrass, there will be decisions to make about whether to spray at all, as well as timing and tank-mix dilemmas,” he says.

Unfortunately, what Mr Myers describes as an “irritating smattering of blackgrass” can become a much bigger problem once the weed begins to grow away, with each plant capable of producing 20-30 tillers.

“Even 90% blackgrass control won’t solve the problem in many situations. The remaining plants are quite capable of causing a yield penalty.”
Nick Myers, ProCam

“Even those growers who drilled their wheat a bit later, into good seed-beds, and then applied pre-emergence stacks and sequences are wondering whether their efforts have been good enough,” he adds.

These growers are right to be concerned, he believes, as getting 80% control from this early action isn’t sufficient.

“Even 90% control won’t solve the problem in many situations. The remaining plants are quite capable of causing a yield penalty,” he adds.

However, where stacks and sequences of residual herbicides were applied in the autumn in good conditions, there has been a benefit on other weeds, reports Mr Myers.

“Their effect has been to reduce the overall weed burden and push it a bit later. So that gives growers an opportunity to apply a blackgrass-specific treatment before they have to tackle broad-leaved weeds,” he adds.

So what are the options?

Atlantis is at the top of the list. Even where there’s doubt about its efficacy against blackgrass, it does have activity on other weeds, says Mr Myers, so may appeal to growers for that reason.

“Some will spray it anyway, hoping they get something on blackgrass. Remember that this is your last chance,” he says.

The best results come from applying it when there is active weed growth and a dry leaf surface.

“You need some moisture and sunny conditions, as well as small weeds. That can be a compromise, but spraying needs to take place sooner rather than later,” he adds.

Unite is an alternative choice. “It also needs to go on small weeds as there’s a cut-off of up to GS24 of the blackgrass,” Mr Myers says.

Unite will also control a range of other grass- and broad-leaved weeds and has better tank-mix compatibility than Atlantis.

“Of course, the same restrictions apply, in that growers can only use one ALS inhibitor with grassweed activity on each crop. So it is an alternative to Atlantis, not an addition,” he says.

Otherwise, there are the fops, dims and dens, with products such as Topik being available.

“Unfortunately, ACCase resistance is at such a high level that this group of chemicals often results in very poor control now,” he says.

Other weeds

Cleavers are the other main spring weed target, as they tend to escape the grassweed herbicides, says Mr Myers.

In addition, crane’s bill seems to be on the rise and both polygonums and wild oats will respond to the very cold week at the beginning of February by breaking dormancy.

Wild oats can be picked up by the treatment used for other grassweeds, he says.

“Or there are specific products such as Axial that can be applied in the spring if this control opportunity hasn’t occurred,” he says.

The T0 timing is a good fit for broad-leaved weed control, he points out, with fluroxypyr/florasulam mixes such as Starane XL and Spitfire being very useful where cleavers need controlling.

“Clopyralid can be added to these, if appropriate, to bring in other weeds such as mayweeds and thistle. There’s also the option to use straight florasulam, which tends to be better in cooler conditions,” he says.

Sulfonylurea products such as those based on metsulfuron have a wide-ranging role against broad-leaved weeds. “There are various products that can be used, according to the weed spectrum present,” he says.

But Mr Myers sounds a note of caution about the broad-leaved weed species that are becoming resistant to sulfonylureas, such as poppy and chickweed.

“It’s not a widespread problem, which is good, and it can be kept that way by using mixes of actives and robust rates.”

In these weeds, target-site resistance has been identified, which means control from the sulfonylureas will be very poor if it is confirmed in weed populations.