Thistle patches need flagged in beet crops for future control

UK - June 05, 2006

Marking out patches of thistles now could reduce sugar beet yield losses later in the season by making it easier to check for regrowth and spot treat. 

“Spot treating thistles with DowShield (clopyralid) is common practice, usually over two applications.  But growers can fail to fully control thistles in sugar beet because they are so difficult to spot on the second application,” says Martin Lainsbury, BBRO’s technology transfer officer. 

“The thistle foliage collapses back into the crop so identifying regrowth even from the sprayer or tractor cab is hard work as the sugar beet canopy has closed over.” 

For a permanent kill of thistle and maximum yield response the second application of Dow Shield at 1.0 l/ha some three to four weeks after the first application of 0.5 l/ha is essential.  

“Sugar beet growers need to achieve 70 t/ha to match the best wheat margins. It’s well established that even very low populations of thistles can cause heavy yield losses in sugar beet crop. A normal sized thistle patch of 4 stems/m² can cause losses of up to 4 t/ha.”   

Mr Lainsbury advises growers to clearly mark out thistle patches at the first application to ensure all the problem areas are successfully treated.  He suggests simply marking thistle patches with stakes or flags or precisely position patches onto a field map with a hand-held GPS receiver, for use in the sprayer cab later.