Timing critical for blackgrass control

Timing of herbicide application and delayed drilling is crucial for effective blackgrass control – this is the advice being given to growers as they enter one of the most crucial stages in controlling the grassweed.


According to combinable herbicide’s manager Chris Cooksley at Bayer CropScience, evaluating germination data of blackgrass gives you the main knowledge needed to time cultivations, drilling and pre-emergence herbicide applications to best effect.


“On average, less than 5% of viable blackgrass seed germinates in August. More than 20% germinates in September and again in October. Germination rates then tail off in November when 5-20% will emerge.”


Using this information you can time your glyphosphate application to take out the highest number of blackgrass seedlings as well as timing your pre-emergence sprays and when to drill.


NIAB TAG agronomist Andrew Chell believes delaying drilling takes a lot of nerve, but will pay dividends this autumn. He advised drilling the worst fields in October.


“It’ll allow 45% of blackgrass to be taken out with a non-selective herbicide. If you drill earlier more blackgrass must be dealt with in-crop,” said Mr Chell.


“You can’t go on too early with Liberator, it can follow the drill,” he added. “Pre-emergences are really important and catch October-November germinators, killing them or making them susceptible to post-emergences.”
Chris Cooksley, Bayer CropScience

Following drilling, speed is vital when applying pre emergence with Mr Chell advising application within 48 hours of drilling.


Mr Cooksley explained the problem with going on too late when blackgrass had emerged means 10-20% efficacy could be lost.


“Residuals such as Liberator (flufenacet + diflufenican) are taken up through roots and shoots as they grow through the soil layer that contains the active substances. If the shoots are above the soil surface it is likely the roots are beyond the reach of the product too.


“You can’t go on too early with Liberator, it can follow the drill,” he added. “Pre-emergences are really important and catch October-November germinators, killing them or making them susceptible to post-emergences,” he added.


When considering the timing of post-ems it’s growth stage and growing conditions that are important.


“Atlantis (mesosulfuron and iodosulfuron) and other post-emergence products work best on actively growing blackgrass plants at the one to two leaf stage,” said Mr Chell.


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