Control thistles to combat orf

UK - May 26, 2009

Getting rid of thistles in sheep pasture with a herbicide such as Thistlex, significantly reduces the spread of orf says Duncan Connabeer, a grassland weed specialist for Dow AgroSciences. 

“Orf costs the Welsh sheep industry dearly in vets’ bills, poor animal performance and lost days’ work for staff who unfortunately pick up this highly contagious virus,” says Mr Connabeer. “Sheep become infected when they brush past sharp objects such as thistles, which act like dirty hypodermic needles, injecting and spreading orf within the flock.”

With no effective treatment once sheep develop the disease, and preventative vaccination failing to offer long term control, removing the thistle population is the best way of reducing the risk of infection.

David Hormann farms 106 ha near Llandovery in the Brecon Beacons National Park, with 300 Lleyn and crossbred ewes as well as 40 Limousin cattle. The lambs are finished on the farm.

Orf had been a problem for several years, and Mr Hormann was vaccinating routinely. However, after using Thistlex to tackle creeping thistles on sheep pasture six years ago, the incidence fell dramatically,

“Five years ago half our lambs were affected,” says Mr Hormann. “But by killing the thistles we removed the main way the virus spreads, and for five years did not have to treat at all. We saved money on the vaccine and the lambs were in much better shape at weaning.

“We had tried to get rid of thistles before with MCPA – but by late summer they came shooting back,” Mr Hormann explains. “By the next spring it looked like they had never been treated. Thistlex gives complete control for two to three years, with just a bit of spot treating required in year four – that’s all.”

Mr Hormann carries out contract spraying for other producers in the area, and says the effect Thistlex has on reducing orf is clear to see on other farms, not just his. “Where fields have been sprayed lambs stay orf-free; where they have not been sprayed, orf remains an ongoing problem.

For more information on thistle control contact the Dow Hotline on tel: 0800 689 8899.