Thistles sap cereal yields and threaten single farm payments

UK - February 23, 2006

Leaving thistles to infest cereal crops could jeopardise single farm payments as well as depressing yields. 

Under Single Farm Payment cross compliance rule a grower must take all reasonable steps to prevent the spread of certain weeds including spear thistles, creeping thistle, common ragwort, broadleaved dock, and curled dock, on his, and onto adjoining land. 

The rule applies to all land, including cropped land, fallow land, permanent pasture and temporary grass, set-aside land, countryside stewardship land schemes, and statutory buffer zones adjoining hedges and ditches. 

Perennial thistles and annual sow-thistle seedlings are more prevalent than usual following the unusually warm autumn temperatures, says Dow AgroSciences’ Rene Pollak. However, control options are limited. 

He advises using Dow Shield (clopyralid) at 0.35 l/ha, from GS12 up to, and including, GS32.   

Sulfonyl-urea herbicides offer highly effective thistle control in cereal crops. However, there are restrictions on their use, in sequence with Atlantis, where the following crop will be a broadleaved break crop.  And this season many growers have opted to use Atlantis to control resistant blackgrass. 

“Alternatives, such as bromoxynil, are not effective once thistles have more than two true leaves.  The hormone herbicides MCPA and CMPP are an option, but their use is limited by Voluntary Initiative guidelines and they have the potential to reduce crop yield if applied after GS 30 at the rates needed for reliable thistle control.  This leaves only one herbicide which, fortunately, is a well-proven thistle killer - Dow Shield.  

“Growers cannot afford to ignore thistles.  Even without the SFP rules, both weed species are highly competitive in cereals. They are both a serious threat to yield, and will hamper harvesting,” says Mr Pollak.