In the bleak mid winter, there is still opportunities for weed control in wheat

The late season has meant that little weed control has been applied to date in wheat and those recommendations that have been made will probably have to be changed as conditions and label restrictions dictate, says Reuben Morris, Technical Manager for Cropwise.

"Wheat crops fall into two distinct categories this year. The first on light well draining land was drilled in good time and is growing well. Crops on heavy land were drilled late and have been slow to develop. One reason that these crops haven’t been treated with a herbicide is that they are not big enough."

Dr. Morris points out there are large acreages of wheat that have been totally unsprayed to date and that there will be a large spray opportunity to go for in January/February time, providing the rain stops falling.

"Last year was the first year we used flumioxazin, SumiMax, and it performed well on Annual Meadow-grass and a good range of broad-leaved weeds when applied in February-March time. If we have a dry and cool February, there will be plenty of opportunity to apply this herbicide this winter. And with the slower growth and moisture it could do an even better job. Unlike flufenacet-containing herbicides that can’t be used after the 31st of December, flumioxazin has a growth stage cut off of 5 leaves on the main tiller (with no date cut-off), which means growers can continue to use it through the winter period," says Reuben.

Dr. Morris offers some pointers for SumiMax users. "It doesn’t have activity on wild-oats and would not be able to cope with heavy populations of black-grass alone, although it is from a different group to other grass-weed herbicides. You should also stick to the full rate for best performance. I would always use it its full rate of 100 ml/ha. Normally it would be applied alone, with no other herbicide partner, but it is usually mixed with an insecticide, preferably a flowable or EW formulation, and with manganese. It is important that the tank is treated with a proprietary tank cleaner after use."

At the start of the New Year many, if not all, weed control recommendations made in the late autumn will have to be reviewed and reconsidered. The late autumn didn’t present many spray opportunities, but the early New Year may well do so, says Dr. David Stormonth Technical Manager of Interfarm UK Ltd.

He advises growers not leave it all to Atlantis which will need to be applied much later in the year when the crop and weeds are actively growing, but to consider using a robust "holding" spray such as flumioxazin until the programme is completed at the beginning of spring.

"SumiMax can be used well into the New Year as its cut-off is according to crop Growth Stage - before GS 15 or five leaves on the main tiller and not according to any calendar date. Other herbicides, particularly those containing flufenacet, have an end of year cut-off date for use, meaning that they can’t be used after the 31st of December."

"SumiMax, which is a contact and residual acting herbicide, works well in the cool and moist winter conditions. The cold weather this year has meant that crops have had the opportunity to harden off, an opportunity that they didn’t get last autumn. Ideally weeds should be between 1-3 leaves at application. But the timing for broad-leaved weed control is not as critical as SumiMax controls a full range of broad-leaved weeds from germination to the 4-6 leaf stage, depending on the species. It has an excellent broad-leaved weed spectrum including charlock, chickweed, cleavers, poppy, field pansy, fumitory, groundsel, speedwell, mayweed, red deadnettle and Shepherd’s purse," David says.

Where grass-weeds are an issue, SumiMax can be tank-mixed with a suitable graminicide in order to strengthen its grass-weed control. "Applied at the 1-2 leaf stage SumiMax will give control of 90% plus of Annual Meadow-grass on its own. It will also give a good effect on black-grass. If weed populations are particularly high or if conditions are marginal, you can always add in a low rate of isoproturon or chlorotoluron after the 31st of December," advises David.

SumiMax contains 300 gms ai/litre flumioxazin formulated as a white, non-staining, easy-to-use suspension concentrate, packed in a 500 ml pack. (These features of SumiMax were reported in a survey as being of major benefit.) Recommended in winter wheat, it can be used pre or post-emergence up to before GS 15 for the control of a wide range of broad-leaved weeds, including charlock, chickweed, cleavers, common field speedwell, common poppy, field pansy, fumitory, groundsel, ivy-leaved speedwell, mayweed, red deadnettle and Shepherd’s purse, and grass-weeds, including Annual Meadow-grass and loose silky bent. It is recommended at 100 ml/ha in 200 litres of water, with one application per crop. It has residual and contact activity. It is compatible with a wide range of autumn products but should not be used with any adjuvants. It can be sequenced with any product including sulphonylureas, but a 14 day interval should be allowed. Flumioxazin is available as SumiMax, Digital and Guillotine.

For further information, please contact Dr. David Stormonth, Technical Manager, Interfarm UK Ltd. on 01354 741414 or 07818 036506 (mobile) or via e-mail david.stormonth@interfarm.co.uk