Bean growers get new option for winter weed control

With simazine set to be withdrawn later this year, winter bean growers need to be looking to adopt alternative herbicide strategies, advises Jim Scrimshaw of PGRO. He reports a SOLA (Specific Off-Label Approval) for Defy in winter beans now gives a new option for pre-emergence weed control this autumn.

Mr Scrimshaw believes the opportunity to drill winter beans into better seedbed conditions, using modern min-till equipment, will enhance the effectiveness of pre-emergence herbicides. "Winter beans are especially susceptible to weed competition during the early stages of establishment and through the winter period," he warns.

He highlights the particular strengths of Defy for cleaver control, along with other important broadleaved and grass weeds - including annual meadow grass, fumitory and forget-me-knot - should enhance winter bean agronomy. "It will prove a useful mix-partner for many of the remaining herbicides and, in well chosen combinations, should be able to offer broad spectrum weed control for most situations." The SOLA permits an application rate of up to 5.0 l/ha.

Mr Scrimshaw points out that the only product for post emergence broadleaved weed control, bentazone, is both expensive and has a limited control spectrum.

TAG agronomist, Jon Bellamy, advocates that in the post-simazine era, bean growers may look at a sequence of straight Defy pre-emergence, followed by carbetamide post-emergence. "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 OSR and charlock which can pose a real threat in winter beans; it is difficult to get the timing right for effective Bentazone applications in the spring."

He adds that the split application strategy will give growers the reassurance of weed free crop establishment with pre-emergence Defy, and then to check they have a decent crop potential before spending on the post-emergence application.

Mr Bellamy believes that for speed and cost most crops in the east midlands will still be established by ploughing in and then leveling or harrowing the soil surface. Where there is still a cloddy surface, spray application will be important to achieve good results.

Syngenta research into pre-emergence Defy application in a range of crops has shown that application using angled nozzles, alternated to face forward and backward along the spray boom, improves overall coverage of the soil surface and clods - resulting in better weed control. Defy may be applied using Hawk nozzles in a water volume of up to 100 l/ha, or using the Syngenta Potato nozzle at up to 200 l/ha.

• Jim Scrimshaw highlights that improved pulse prices have helped margins for winter bean growers this season, with the opportunity now for additional premiums for the variety Wizard, grown for human consumption. "Beans offer many agronomic advantages for growers and still have an extremely valuable role in the rotation."