James Boswell, of distributor Hutchinsons, says that control of this competitive weed used to come out of a chemical can, but with the increased intensity plus widespread resistance to a range of active ingredients, growers must move to cultural control methods for black-grass as their first port of call.
James says that he would normally sit down with his customers and carry out a review of black-grass across the farm. "It used to be a weed of heavy soils and winter rotations, but it is now found across most arable land. We need to get an idea of how intense the infestation is, what has worked in the past and what hasn't. Firstly, I would advise growers to introduce a spring crop, either maize or spring barley. This has a positive effect on reducing the black-grass population, as the majority of black-grass germinates around the 15th October. Germination is strongly influenced by pre-harvest dormancy and peak germination may move later by 10-14 days this year after a cold, damp start to June, meaning delayed autumn drilling will be of paramount importance this year. In really bad black-grass situations, a double spring cropping would be advisable. The worst scenario would be a first wheat with poor black-grass control, followed by a second wheat."
Lo-tillage winter oilseed rape can be a useful alternative crop as it allows the use of different chemistry to that of cereals, namely propyzamide. “This chemical has no known resistance" but chosen fields cannot be carrying significant black-grass seed reserves or it is a doomed strategy, says James.
“Dry conditions will have a negative impact on the use of stale seedbeds, which need moisture for strong impact. The residual herbicide stack applied pre or peri-emergence, and which relies on the active flufenacet either in coformulation with pendimethalin or diflufenican, also works much better with moisture available. Avadex Granules (tri-allate) could be a start to the herbicide programme in cereals, providing another mode of action to integrate into the strategy."
James Boswell reports that the best level of black-grass control “out of the can” nowadays is probably only around 50%, so growers must adopt a positive cultural control strategy.