Residual plus graminicide is best for osr grassweeds

Using a contact graminicide in combination with a residual herbicide could provide better control of key grassweeds in oilseed rape than a residual herbicide on its own, according to latest trials.

Results from three years of work conducted by ADAS, Oxford Agricultural Consultants and distributors found that tank mixes of Crawler (carbetamide) with either Falcon (propaquizafop), Aramo (tepraloxydim) or Laser (cycloxydim), provided better performance than Crawler or Kerb (propyzamide) alone.

“Under ideal, low temperature conditions, there is little to choose between Crawler and the more expensive residual product Kerb, in terms of blackgrass control,” Makhteshim Agan’s Jackie Passey explained.

“However, by tank mixing reduced-rate Falcon into a full-rate application of Crawler, trials show you can lift blackgrass control from 60-65% to 95%, at a cost similar to full rate Kerb.” She said the better control was largely due to the sensitising effect of the contact-acting product.

The Crawler/ graminicide mix was best applied from mid-October onwards before canopy closure, as colder soils would prolong the activity of the residual component and take out later-emerging grassweeds, she added.

UAP technical director Chris Bean said the choice of residual depended on local conditions following application. “In a mild, wet autumn, propyzamide, which is less soluble than carbetamide, can provide better residual activity.

“However, in a drier winter, the greater solubility of the carbetamide ensures better, quicker distribution in the soil and better control.”

Mrs Passey said that a 20% fall in oilseed rape area in some regions this autumn meant effective grassweed control in osr would be particularly important in order to reduce pressure in following cereals.

Keep track of what’s going on in the field with FWi’s weekly Crop Watch reports direct from agronomists around the UK.

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