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Wet weather at the end of September has kick started black-grass germination. But growers need to be patient before spraying off then drilling as there is likely to be further germination in October.

Black-grass typically has two flushes, one in late September and another by mid-October. Deciding to drill before the second flush is a recipe for a high weed pressure crop.

“After last autumn, it isn’t surprising to find so many people anxious not to leave their drilling too late this time around,” says Mr Thomas Scanlon of Bayer. “But, on high grassweed risk fields, in particular, all the evidence points to sowing before effectively eliminating the main annual grassweed flush is potentially creating major problems in trying to control grasses post drilling’.

Drilling after 15 October is a good rule of thumb for avoiding any further germination in the crop. But closely monitoring weed germination can allow farmers to pinch a couple of days drilling if they think the second flush is over.

Once the decision is made, having a plan to spray Round Up, drill and then get back with the pre-em within 48 hours gives the smallest window possible for any additional germination.

“If there is a long delay between spraying off and drilling, you always have the option of including an approved glyphosate in the pre-em mix. This is something you should seriously consider wherever drilling is delayed for more than a few days after your pre-planting spray. A lot of black-grass can emerge in a very short time under the right conditions and it won’t be touched by most residuals. So, it can be a valuable extra string to your control bow.”

Mr Scanlon advises growers to use rates of 540–720g /ha when applying Round Up (glyphosate). Using a modern Round Up formulation maximises control giving the winter wheat crop the best possible start. This is especially important because there are reports of noticeably poorer performance being seen from many of the generic alkyl phosphate ester (APE) formulations replacing the now-withdrawn Ethoxylated tallow-amines' (ETAs).

“Attention to detail in spraying practice is every bit as important in making your pre-planting applications work as hard as they can. It really is vital not to rush the job, and get your water volume, nozzle type, spray pressure and boom height spot on.”