In the increasingly tough fight against grass weeds, tackling them early is critical, according to ADAS’ James Clarke.

In most instances, early pre and post-emergence treatments will deliver superior control than approaches based on either “wait and see what weeds emerge” or “delay until all weed seeds have flushed”.

“As grassweeds, especially blackgrass, pose an increasing challenge, farmers need to use the whole array of control measures including crop rotation, cultivations and sowing date. However, when it comes to using herbicides the key is a full programme and early applications,” said Mr Clarke.

The pre-emergence treatment is the vital foundation of any weed control programme and early application will pay dividends in most instances.

“Putting the herbicide in place before weed seeds germinate will ensure the optimum benefit from any pre-emergence treatment,” he explained.

Similarly, autumn post-emergence sprays perform best when applied relatively early to small and actively growing weeds. Not only will this control weeds, but it will also protect against yield loss as infestations compete with the crop.

“There is a misconception that delaying post-emergence treatment will allow more weeds to emerge,” says Mr Clarke. “Most grass weeds emerge in a fairly short period of time. Ryegrass, for instance, is nearly all autumn germinating. There are usually few late emergers.

“Those that do emerge late are much less competitive and produce less seed. It is far better to get good control of the bulk of the flush early, rather than wait for every last seed to germinate and get poor control of them all.”