25 February 2000

Impuls hits pea weeds early

By Andrew Swallow

PEA weed control in one early post-emergence application, even where cleavers and volunteer oilseed rape are present. That is the claim BASF makes for its newly launched herbicide Impuls (bentazone + pendimethalin).

Combining the proven residual herbicide of Stomp (pendimethalin) with the contact active of Basagran (bentazone), the new twin-pack products unique first to third node timing takes out most weeds before they start to compete or become difficult to control.

That makes pre-emergence and late post-emergence sequences unnecessary for broad-leaved weed control, maintains product manager Diane Lovesy. "It is an opportunity for a new weed control strategy in peas."

Previously, the lack of any approved herbicide before second node stage of the pea crop led many growers to use pre-emergence products. But a recent agronomist survey showed 50% of pre-emergence treated crops received a follow-up post-emergence spray.

"And that could be a lot higher in a dry spring. The problem is the most frequently used pre-emergence products miss cleavers and volunteer oilseed rape," she explains.

Cleavers are controlled up to the four-whorl stage which would be after the 14-21 day window for application of Impuls anyway, she continues. A leaf-wax test on the peas is not required unless the crop is showing signs of stress.

"A key point weve had to look at is crop safety – growers are nervous of such an early application. But the maximum crop damage weve had in 26 trials is 1%."

The third-node cut-off date for the product means black-bindweed is only rated as moderately susceptible, since late emerging plants can escape control, notes PGROs Cathy Knott.

"If black-bindweed is there at the time of application you get 85-90% control," she says. Knotgrass is rated as susceptible up to two true-leaves.

Recommended application rate is 1.5 litres/ha of Impuls A (bentazone) plus 2.0 litres/ha Impuls B (pendimethalin). Each twin-pack box will treat 4ha (10 acres) at these rates. Reduced rates are regarded as a false economy as incomplete weed control could add desiccant and aggravation costs at harvest.

Though formulations are the same as the stand-alone products, growers tempted to try mixing their own version are warned they would be making an illegal application and could jeopardise crop assurance.

"Pendimethalin does not have a post-emergence recommendation in peas, so it would be an illegal use of the product," says Miss Lovesy. Adjuvants are not recommended either, as damage to the leaf wax would increase crop damage.

Price has yet to be fixed, but will be pitched to offer growers about a 20% saving on a common reduced-rate pre and post-emergence programme says BASF herbicides manager Andrew Jones. &#42

IMPULS CONTROL

&#8226 Broad-leaved weeds in peas.

&#8226 1st-3rd node timing.

&#8226 Cleavers and vol OSR controlled.

&#8226 No tank-mixes.

&#8226 No insecticide or graminicide for 7 days after Impuls.

&#8226 Not on soil >10% O.M.

Peas at first node like this will be ready for spraying with BASFs new early-application herbicide Impuls, says product manager Diane Lovesy.