RAPID DEVELOPMENT of oilseed rape crops in many areas means growers must focus on getting the best from post-emergence herbicides this autumn.

But, with crops and weeds growing rapidly, many growers may have already missed the optimum post-em timing, some experts have warned.

“The time has come to focus on early post-emergence applications of herbicides and in particular how to get the best from them under this year‘s conditions,” said Diane Heath from BASF.

Key competitive weeds that need early control in OSR are blackgrass, cleavers, chickweed and poppies, she said.

Yet higher dormancy in many weed species means growers can wait until later in the autumn or the spring for reliable cleaver control, according to Dow AgroSciences.

The company recommends using Galera (clopyralid + picloram) in the autumn, only if there are very high populations of cleavers suppressing the crop.

But early autumn control can help prevent direct yield loss from competition, seed contamination and reduce the weed burden in the following crop, Mrs Heath added.

She recommended using either Butisan S (metazachlor), Katamaran or Novall (metazachlor + quinmerac) as soon as crop rows are visible.

Latest Crop Monitor reports indicate oilseed rape crops are growing well across the country, apart from some eastern areas that suffered from poor emergence due to dry seedbeds in September.

In most of England September sown crops are at the 3-4 leaf stage, apart from some northern crops, which are slightly less developed.

Crops sown in late August are further ahead with six or more leaves, the results also show.