Sorting out blackgrass fact from fiction

UK - October 26, 2006

There is a lot of talk about black-grass resistance, but sorting fact from fiction is a challenge that one agronomy company is taking seriously. 

“With so much advice and information flying around about black-grass getting the basics right has never been more important with black-grass control,” says Agrovista’s technical manager Mark Palmer.   

“From resistance strategies to herbicide choice; from choice of timing to cultural control, Agrovista is now ensuring that all staff are fully briefed and regularly updated with information drawn from own experience, independent trials as well as manufacturers’ product stewardship. Our aim is to give our customers the latest facts for their benefit.” 

With increasing black-grass resistance to a range of cereal herbicides, including Atlantis, the use of break crops, such as oilseed rape, becomes increasingly important.   

“Residual herbicides for winter oilseed rape and winter beans are the only ones still giving complete control of all resistant black-grass strains,” advises Dr Palmer.   “As long as it is used correctly, the active ingredient propyzamide (found in Precis) has provided consistently high levels of control.” 

Agrovista has worked with Dow AgroSciences on fine-tuning new information and advice on the use of propyzamide following five years of comprehensive trials with ADAS into recommendations on-farm.   

“This autumn we will use new information to ensure growers get the best results,” says Lincolnshire-based Agrovista agronomist Andrew Mellors. “With soil and air temperatures still well above average and winter oilseed rape growing rapidly we advise growers to be patient and wait until mid-November before applying propyzamide.” 

Mr Mellors has seen weed control from all late summer and autumn-applied herbicides breaking down due to the weather conditions.  Only careful application of later sprays will prevent poor weed control.   

“Applying propyzamide too early may result in reduced weed control. Lack of moisture and a high soil temperature reduces its residual action,” says Mr Mellors. 

Grower Simon Harrison relies on winter oilseed rape as a cleaning crop on his resistant black-grass infested heavy Lincolnshire fields.  Mr Mellors first recommended Precis on winter rape two years ago, combined with a move to a min-till system pre-planting.  

“Simon now achieves 100% control of resistant black-grass using Precis,” says Mr Mellors.  “The key to consistently good black-grass control with the herbicide is to use very shallow minimum tillage, and apply only after the ground is well wetted and cool which, in most seasons, is from mid-November. This advice is backed up by solid trials evidence from Agrovista, Dow AgroSciences and ADAS.”   

To ensure Simon’s oilseed rape crops did not suffer from early grass and broad-leaved weed competition Mr Mellors recommended pre-emergence Treflan with Butisan which, he says, reduced the average 250 black-grass plants/m².  An early post crop emergent application of a graminicide such as Aramo suppressed the black-grass further and controlled early emerging volunteer wheat.  This has given Simon time to wait for the correct conditions to apply Precis and fully control the black-grass.  

“With disappointing results on black-grass control from Atlantis last season, it is a relief to have the guarantee of Precis controlling all the black-grass as well as other grass weeds such as wild oats, brome and ryegrass.  Long may it last,” says Andrew Mellors.