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Test results for black-grass viability - 3 July update

Agronomy Issues
Black grass heads and seed shedding

Black-grass seed heads have continued to shed a high proportion of their viable seed over recent days. Viability testing of black-grass seed heads from the Syngenta Barton Black-grass Innovation Centre, near Cambridge, has shown significant differences between black-grass heads in winter and spring crops.

Reports indicate many growers were reluctant to spray off badly infested areas of black-grass in crop this season - given the low area of winter wheat in the ground and earlier drought protential pushing down yield prospects. That could add a further complexity to black-grass control programmes this autumn.  

Scroll down for earlier updates and more information

** Week 5 - 3 July 2020 -  In the winter wheat crop, so many of the black-grass heads have now shed their viable seed onto the soil surface that viability testing of remaining heads is no longer relevant. In the spring crop, there is huge variability among black-grass heads. Whilst shedding of viable seed has been identified in 13% of heads, on average only 1% of seed has been shed from each head. Furthermore, viability of seed was 23%, which was lower than last week, but possibly explained by the variability in the age of the heads in this crop. Ripening of black-grass in the spring crop will be protracted. **

 ** Week 4 Phase 2 update - 30 June 2020 - Black-grass seed heads in winter wheat have continued to shed seed; an average of 26% of the head has shed viable seed onto the floor, with some heads up to 80% shed. Viability of the remaining seed is 46%. Black-grass seed heads in the spring crop are extremely variable. Some 37% of heads have started to shed seed, but on average only 3% of seed per head has dropped.  The age of heads in the spring crop is also far more variable, with an average 35% of seed remaining viable. Ripening of black-grass in the spring crop is expected to be protracted. **

** Week 4 - 26 June 2020 - Viable seed numbers of black-grass collected in winter wheat have reached a plateau. All heads collected have started to shed, with an average 68 percent of seed is viable. The range of seed viability was 17 to 91%.  Ripening of black-grass in the spring crop has continued apace. Seed viability has rocketed from an average of 2% last week, to 51% in the latest round of testing; the range is two to 87%.  Furthermore 63% of heads were identified to be already shedding. ** 

** Week 3 Phase 2 update - 19 June 2020 - Ripening now showing 97% of heads shedding seed. An average 61% of seed is now valuable - with a range of 24% to 77%. The number of samples in each viability category has tightened week on week as maturity increases (see below). **

Black-grass viability variation 3

19 June - NEW SPRING CROP SAMPLING - First sampling of black-grass heads in spring wheat show just 2% of seeds were viable on average (below) - with a range of 0 to 14%. Still time to take burn out action on infested areas. 

Black-grass seed heads from spring wheat

** Week 3 - 15 June 2020 - Ripening of heads is continuing at speed. 80% of heads collected have started to shed seed. All heads tested now have at least 24% viable seed. Up to 70% of seeds per head now viable, with average seed viability of 53% **

** Week 2 phase 2 - 8 June 2020 update - no further increase in seed viability - still 16% on average viable - range of 0 - 37%. More heads showing trend to higher percentage of viable seeds (see grapic below) **

viability vision 8 June graph

** Week 2 Testing - 4 June 2020 - viability more than doubled in a week - 16% of seed on average viable - range of 0 up to 36% **

** Week 1 Testing - 1 June 2020 - 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 at the end of May, with an overall average of 7%. Some heads, however, have yet to show any viable seeds. **

Follow updates of ADAS results for black-grass viability testing - #viabilityvision

Black-grass patch spraying

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.

Patch spraying of black-grass infestation was seen by growers as an essential integrated crop management technique, second only in importance to spring cropping, according to the Syngenta State of the Nation Survey on black-grass populations. It was utilised by 80% of growers who responded to the survey.

Black-grass IPM techniques

Dormancy set

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, 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," advised Miss Wood.

“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.” 

Georgina Wood

Burn out action

Miss Wood (above) 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.”