8 September 1995

Oil additive

claims extra weed control

RECENT work by one adjuvant maker suggests its product may enhance the effect of a widely-used autumn herbicide against broad-leaved weeds, particularly field pansy.

Trifluralin (as in Treflan) is often used in weed control programmes for autumn-sown cereals, usually as a companion to isoproturon.

Now Microcides Steve Sylvester claims two years work with the firms Codacide oil additive indicates it provides a useful boost to control, almost certainly because it cuts volatilisation of the herbicide.

David Farrant is technical adviser with trifluralin supplier DowElanco. He says trifluralin was originally developed for use on non-cereal crops in spring. Applied at that time, it needs incorporating into the soil to prevent breakdown by ultraviolet light.

He adds that using it as a surface treatment without incorporation on oilseed rape in August and September proved ineffective -probably because summer/early autumn sunshine is too strong.

"But if you use it in October and November when there is less light and more moisture it works quite well as a straightforward surface application – even better in winter."

Pre-emergence Treflan (trifluralin) is particularly useful in cereals against annual meadow grass, claims Mr Farrant. It also controls a wide-range of broad-leaved weeds including chickweed and speedwell, but not brassicas, mayweed or groundsel.

He reserves judgement on the Microcide claim until seeing detailed trials results. "An oil might help to prevent loss through UV light," he says. That could make application to earlier cereal sowings more effective, and might even make it useful in oilseed rape.

Another possibility is that the oil could give trifluralin some post-emergence activity, Mr Farrant suggests. &#42

Specific advice to include adjuvants with autumn herbicides is increasing. But straying from label guidelines could prove costly.