Dow AgroSciences’ Hotline is coping with numerous queries on how to control broad-leaved weeds that have come through pre-emergence herbicides in winter oilseed rape and are potentially affecting yield and interfering with crop management. “It is an unusual situation this year,” says Sarah Hurry of Dow AgroSciences, “But we are getting a lot of telephone calls about broad-leaved weeds that have come through the pre-ems, probably due to the dry conditions in September and which need to be controlled now. The main weeds seem to be mayweeds, groundsel, thistles, marigold, redshank – odd as it is usually a spring germinator – fumitory and fool’s parsley.”
Sarah remarks that some growers have rape crops which are already advanced in terms of size and leaf numbers, but they don’t want to wait for a propyzamide application which is normally in November when conditions are suitable for this active. “We no longer have registration for any straight clopyralid herbicides, including Dow Shield, for use in the autumn in rape any more. Luckily we have an autumn solution in Galera, based on the active ingredients clopyralid and picloram – a proven post-emergence herbicide to control mayweeds, cleavers and other broad-leaved weeds.”
She explains that the spray window for Galera is from the 4 leaf stage of the crop to before flower buds just visible above the crop canopy. “Most rape crops are now beyond this stage. It also works well when crop and weed are growing well, which they are. In terms of target weeds, cleavers and mayweeds are label recommendations, but anecdotal information would include all the weeds we have been asked about – thistle, fool’s parsley, fumitory, groundsel, redshank, sow-thistle – as well as black nightshade, black bindweed, coltsfoot, volunteer peas, volunteer beans and weed beet. Galera would be expected to deliver good activity on all these non-label weeds.”
