Timing key to cleavers contrrol in oilseed rape

UK - January 20, 2006

Cleavers are widespread in this year’s winter oilseed rape crops so growers should be prepared to spray as soon as the weather warms up, according to Dow AgroSciences.  

“It just takes a brief warm spell in the next six to eight weeks and cleavers will take-off, competing with the oilseed crop,” warns Dow’s technical specialist Rene Pollak. 

Mr Pollak recommends Galera (clopyralid + picloram) to suppress cleavers and control any mayweeds and sowthistle. However, timing is critical and in recent years conditions have been right for its use in early February. 

“I’ve seen growers caught out in the past couple of seasons. When the weather warms up, the optimum winter oilseed rape growth stage for Galera has sped by,” says Mr Pollak.  “But remember that Galera works most effectively in warmer conditions, ideally above 6°C during the day.  Sharp frosts, during or after treatment, are likely to reduce activity against cleavers.” 

If cleavers are frost-hardened, wait for the first new growth on cleavers to ensure good herbicide uptake.  If the crop is open, having lost many of its leaves to frost, then the cleavers should be a good target.  In thin non-competitive crops just one plant/m sq can cause a 5% yield loss.  The very best results have been achieved where the crop canopy closes over two to three weeks after treatment, enhancing Galera’s activity.   

If the crop is forward and thick, cleavers can still be a problem.  Yield losses occur with populations as low as 3 plants/m sq as cleavers continue to grow, even in poor light conditions. 

“Canopy penetration by the spray is essential to reach the target.  It is most important to follow label recommendations and apply Galera in a minimum of 200 l/ha of water as a medium spray,” advises Mr Pollak.