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Plan now to deal with potentially High Levels of OSR Weeds
Date added: 26/02/10 |
Forward planning will be essential this Spring if oilseed rape growers are to maximise use of the short spray window available to control the high levels of weeds predicted, warns Dr. David Ellerton of Procam UK Ltd.
“Most weed control in oilseed rape is done pre-emergence, but there are usually some stragglers to control or some spring germinating weeds to sort out in the spring.
“Metazachlor-based herbicides work very well, but some areas of the country suffered dry conditions at planting and so some growers didn’t manage to apply their full programme this season,” he says.
These drier areas didn’t get much moisture until November when the temperatures were rising and Kerb/Crawler products were supposed to be applied. Then we had the coldest winter for many years.
“We have now run out of time for Kerb and for Crawler. A lot of herbicide was meant to go on, but not all did. So this spring there is probably more weed control to do than for a number of years.
“It is normally the large fleshy or climbing weeds that are the main target weeds in the spring – weeds such as creeping thistles, sow-thistles and cleavers. These weeds are competitive to the crop and cause damage at harvest when they interfere with harvest.”
Dr. Ellerton points out that the choice of spring-applied herbicides in oilseed rape is relatively limited.
“There is Dow Shield (clopyralid)) for thistles and mayweeds or Galera (clopyralid and picloram) which has a broader weed spectrum including cleavers, sow thistles and groundsel. Both these herbicides need active growth to work well and this means that conditions must be warm enough for both crop and weeds to be growing.
“The manufacturers recommend that they are applied when day and night temperatures are above 6°C and rising. In practical terms, the warmer the weather, the better the results.”
The spray window for Galera and Dow Shield can be short and will probably be so this spring, Dr. Ellerton warns.
“If you have to wait for the warmer weather and then apply the products within their cut-off, which is up to flowers buds visible above the crop canopy, this can be a short time, especially once nitrogen has been applied and crops start to move again.”
Growers should go out and look at their rape fields now and make a note of which fields will require treatment once the warmer weather arrives, he says.
“It makes sense to order the necessary product and have it ready in store when conditions are more appropriate for application.”
Another spring applied herbicide is Fox (bifenox) to control charlock and some cleaver control. But Dr. Ellerton warns that this contact-acting herbicide has a SOLA only for use in oilseed rape so growers must have the necessary documentation before considering using it.
“There is also the option of using a graminicide in rape in the spring for tidying up grass-weeds. These contact-acting herbicides need to be applied before the crop canopy closes over and with the spectre of weed resistance, care is needed.”
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