Testing decisions for black-grass viability

Cereal growers are being urged to spray off patches infested with black-grass now, before more plants set viable seed. The stress of hot dry weather has brought forward seed maturity, with viability set to accelerate over the next few weeks.

Viability testing of black-grass seed heads from the Syngenta Barton Black-grass Innovation Centre, near Cambridge, has shown up to 23% of seed is already viable in some heads, with an overall average of 7%. Some heads, however, have yet to show any viable seeds.

Patches of heavy black-grass infestation mapped for burning out with glyphosate need to be targeted quickly, advocated ADAS grassweed specialist, Dr Sarah Cook.

“Continued hot dry weather means we expect to see the results from viability testing accelerating,” she reported. “With the range of viability we’ve seen, growers can still have a beneficial effect, but don’t leave it too late.”

She believes that viability testing of the Barton black-grass population gives a good indication of the situation across the eastern counties.

The early timing of black-grass seed viability this season is also expected to have an impact on subsequent seed dormancy, warned Syngenta Technical Manager, Georgina Wood. Whilst weather conditions around Wimbledon Week are typically considered to define rates of black-grass seed dormancy, it could be set two to three weeks earlier this year.

“With the forecast settled for continued hot and dry weather for the foreseeable future, the early indications are for relatively low dormancy year – with the implications that has for cultivation, establishment and herbicide options,” she said.

Syngenta grass weed experts will continue to monitor and report black-grass seed viability with ADAS over the coming weeks, followed by dormancy testing of seed to give growers an in-season update of the challenges they are facing this autumn.

“Previous years of integrated weed management trials at the Barton Black-grass Innovation Centre have given a clear picture of what techniques can help growers manage difficult weed populations.

“In-season testing of seed dormancy enables growers to take appropriate action to better target black-grass in the autumn and help enhance long term sustainable population management.”

Burn out action

Miss Wood added that where black-grass weeds are currently stressed and heading into senescence, growers need to focus on glyphosate application techniques to aid rapid herbicide uptake for more successful burn-out results.

“Pay attention to application rates, water volume, use of adjuvants and nozzle choice to hit weeds as effectively as possible,” she advised. “But above all, the key is timing to minimise the risk of viable seed set.”