Winter bean growers will have another pre-emergence weed control option this autumn following Specific Off Label Approval (SOLA) for Defy (prosulfocarb).

The product is effective against a range of broadleaved and grassweeds, but has particular strengths against cleavers, annual meadow grass, fumitory and forget-me-knot, according to the PGRO’s Jim Scrimshaw.

“Winter beans are especially susceptible to weed competition during the early stages of establishment and through the winter period.”

Defy would make a useful mix partner for many herbicides following the withdrawal of simazine later this year, he added. The only post-emergence broadleaved weed killer was bentazone, which he said was expensive and had limited control spectrum.

Post-simazine, bean growers could use a sequence of straight Defy pre-emergence, followed by carbetamide post-emergence, added The Arable Group’s Jon Bellamy.

“The two products are very complimentary in their different modes of action on blackgrass and will effectively cover most other problem weeds. Defy looks very useful on cranesbill, cleavers, volunteer oilseed rape and charlock which can pose a real threat in winter beans.”

The SOLA permits application rates up to 5.0 litres/ha and Syngenta research has found that spray coverage – especially on cloddy seedbeds – is improved by using angled nozzles, alternated to face forward and backward along the spray boom.

Defy can be applied using Hawk nozzles in a water volume up to 100 litres/ha, or the Syngenta Potato nozzle at up to 200 litres water/ha.