Many oilseed rape crops are being swamped with a wide range of broad-leaved weeds and growers are being urged not to wait before treating.
The Dow AgroScience technical hotline has been inundated with queries on how to get on top of the weeds, which have come through pre-emergence herbicide treatments.
Dry conditions through much of the autumn have hindered the uptake of pre-emergence residual herbicides, leading to mayweeds, groundsel, thistles, marigold, redshank, fumitory and fool’s parsley establishing in crops.
Many growers will be reluctant to add another sprayer pass to their autumn workload, but Dow’s Sarah Hurry says that growers should treat now rather than wait for the correct conditions for propyzamide applications.
- AstroKerb – propyzamide + aminopyralid
- Galera – clopyralid + picloram
- Kerb Flo 500 – propyzamide
“Although straight clopyralid products are no longer approved for autumn use in oilseed rape, we have Galera, which has proven post-emergence activity on mayweeds, cleavers and other broad-leaved weeds,” she says.
The product can be applied to crops from the four true-leaf stage to just before flowerbuds are visible above the canopy and in the kind autumn, many crops are at or beyond the four-leaf stage.
Ms Hurry explains that the product works well when the crop and weeds are growing well, which is the case currently, providing ideal conditions for maximum efficacy.
“The Galera label notes good control of cleavers and mayweeds, but anecdotal evidence suggests strong activity on all weeds that are causing oilseed rape growers headaches this autumn.”
As well as thistle, fool’s parsley, fumitory, groundsel, redshank and sow-thistle, that list includes black nightshade, black bindweed, coltsfoot, volunteer peas, volunteer beans and weed beet.
Although AstroKerb and Kerb Flo 500 will give growers some activity on broad-leaved weeds, their main strength is on grassweeds such as blackgrass.
“AstroKerb delivers the same weed control spectrum as Kerb Flo 500, with the addition of mayweed species and common poppy. We would also expect activity in sow-thistle and groundsel,” says Ms Hurry.