Pea growers turn to post-emergence herbicide options

With virtually no rain across eastern and southern England since March, the results of pre-emergence residual herbicides have been severely compromised on dry soils. Growers looking to now use a post-emergence Skirmish and bentazone mixture will need to do so before the crop reaches the 2nd node stage.

"Most pea crops were drilled into excellent seedbeds and generally don't look too bad," reports Jim Scrimshaw of PGRO this week (30 April). "But they need rain soon, and that could also trigger a real flush of weeds." With little movement of pre-emergence herbicides into the germinating weed root zone where they take effect, post-emergence applications are now the key option.

"Some growers had waited for forecast rain since drilling before applying their pre-emergence herbicides, but the crop is up and we are into post-emergence treatments," he advises. "The good news is that weeds have also been slow to emerge; if there are none present then there is no advantage in adding the contact bentazone with Skirmish," he adds.

If there are weeds competing with the emerging peas, Syngenta Herbicide Technical Manager, Jason Tatnell, advocates growers include 0.3 kg/ha of bentazone with Skirmish whilst weeds are still small, but increase the rate to 0.6kg/ha if weeds are larger and growing aggressively on moisture retentive soil.

"Moisture in the seedbed is required to kick-start the residual activity of Skirmish, which will control a broad-spectrum of late germinating weeds when it eventually rains," he adds.

Mr Scrimshaw reports many growers did at least use up stocks of those pre-emergence herbicides in their last season of permitted use - such as Opogard - which would otherwise have incurred disposal costs. "The options for post-emergence weed control will be further reduced from next year, when cyanazine is no longer available and further mix options are lost," he adds.