Effective volunteer cereal and grass weed control in break crops required to fully benefit from reduced ‘Take-all’ in following wheats

UK - September 20, 2006

Removing volunteer cereals and grass weeds with residual soil-acting herbicides in break crops will significantly reduce ‘Take-all potential’. 

Many growers have incomplete control of these weeds.  “Just a few volunteer cereal plant or grass weeds in rape stubble can maintain the ‘Take-all’ fungus in the oilseed rape crop,” says Bill Clark, a senior plant pathologist at ADAS Boxworth.  

“The following wheat will become infected from direct contact between infected and new crop plant roots.  The disease tends to be a greater problem in minimal cultivation systems with high soil organic matter close to the surface.   First wheats may not show obvious symptoms of Take-all but the disease may be present on the root system, carried over on grass weeds in the previous crop. The following second wheat will suffer far higher yield reductions than if it followed a ‘clean’ first wheat.”  

Experiments at Rothamsted Research confirm ‘Take-all’ in second wheats has increased.  The research has also identified grass species that act as hosts to the fungus. 

“Yorkshire fog, brome species and bent grasses are the biggest threat.  Several other grass species including ryegrass and blackgrass act as a host to a lesser degree.  The use of grass cover crops in set-aside in recent years has increased this threat,” says Richard Gutteridge of Rothamsted Research. 

He points out that wheat following a double break builds-up less ‘Take-all’ inoculum than wheat following a single break.  So second wheat are at less risk of severe ‘Take-all’. always yields significantly higher than wheat following a single break.   

He adds that complete control of grasses and volunteer cereals is needed in break crops for the following wheat to achieve its full potential.  This requires a combination of herbicides, including a long-lasting soil-acting residual herbicide. 

Dow AgroSciences sponsored trials work at ADAS Boxworth over the past five years has provided valuable information on effectively controlling grass weeds in the UK’s leading break crop winter oilseed rape.  

Used correctly Kerb Flo (propyzamide) provides almost 100% control of grassweeds including all strains of blackgrass, ryegrass, brome species, and many other grass species. Also, due to its greater residual action over all other soil-acting herbicides, it may provide control of the later germinating volunteer cereals and grass weeds such as soft brome.