Barrie Hunt, UK and Ireland development manager for Gowan Crop Protection Ltd is well aware that most arable farmers, after last year’s difficult planting conditions, will be wanting to plant as much wheat as they can this autumn, but he warns them that early drilling brings a number of problems. “If you look at the germination pattern of black-grass it normally peaks in mid-October, so the earlier you drill the more weeds you will have to cope with within the crop. However with a crop drilled on 15th of October you can deal with much of the black-grass through an application of glyphosate. By bringing the drilling date forward, the amount of black-grass that has to be controlled in-crop escalates and will put pressure on the performance of the herbicide stack applied pre-emergence. Early drilling can also mean dry seedbeds, not ideal for many residual herbicides,” he says.
“Growers need to weigh up their options and the best approach may be to avoid drilling in September. However, you need to be prepared. If you are going early, your pre-ems need to perform well and for a long time, to make sure weeds are controlled. Tri-allate, the active ingredient in Avadex products, has physical chemical characteristics which mean it has a greater tolerance of dry seedbeds than some other autumn herbicides such as pendimethalin, prosulfocarb or flufenacet. Of the Avadex products, Avadex Excel 15G is better suited to drier early season use and growers should aim to apply it within 48 hours of drilling. If it is bone dry and nothing is growing, there is no rush; you can wait for the rain to allow the black-grass to germinate. Avadex Factor fits better on later drilled crops in October/November when there are good pre-em conditions and good seedbeds and moisture.” he advises.
Avadex also has good staying power as indicated by its half-life in soil. Tri-allate’s half-life in soil is around 3 months compared with the half-life in soil of flufenacet which is 20 days and prosulfocarb which is just 12 days. This means tri-allate has good longevity which will be needed in the autumn, especially if drilling earlier.
Although the focus is so often on black-grass, do not forget the excellent wild-oat control that Avadex brings as well as useful activity against rye-grass and brome species.
Recent work by Agherba in Bristol shows that Avadex will control these grass weeds well if conditions are optimal. It also brings a very useful contributory control of some key broad-leaved weeds including cleavers, charlock, chickweed, poppy, field pansy, speedwell, forget-me-not, fumitory, mayweeds and red deadnettle.
“It is good product stewardship that before drilling, growers ensure that their granule applicator is calibrated correctly to apply 15 kg/hectare and that the granules are applied evenly across the boom width. The correct amount of herbicide granule must be delivered down each pipe and Barrie recommends that a patternation test is carried out along with the calibration. “Black-grass is such a competitive weed that accurate and even application is essential,” he says
Avadex granules can be used in all varieties of winter and spring wheat and barley and has EAMUs for winter rye, winter triticale and winter and spring linseed. Avadex Factor can be used in winter wheat, winter and spring barley, with an EAMU for use in winter and spring linseed.