29 December 1995

Clean shave for old mans beard

OLD mans beard is a growing threat to hedges old and new and warrants more research to avoid wasting public money.

So says Hants-based farmer group the Grasshoppers, which is investigating chemical control methods.

Too many growers replanting old hedges and putting in new ones, usually with grant aid, find their efforts thwarted by old mans beard (Clematis vitalba), says research committee chairman Roy Shepherd.

Chris Harper of Manor Farm, Whitsbury, near Fordingbridge, has no doubt that it is a "serious problem". He blames a demise in hedge-laying for the OMB "explosion". "We thought we had the answer in Roundup." But the herbicide provides only temporary respite, the weed re-invading from its extensive root network, he explains.

Three years Grasshoppers-funded work by David Clay of Avon Vegetation Research has found some alternatives. But none gives adequate selective control within an existing hedge – the most difficult challenge.

"Old mans beard can be really quite debilitating. You can get whole areas completely suppressed which may never revive," says Mr Clay. Wiltshire FWAG officer Andrew Moorhouse says the plant has few virtues apart from its fluffy autumn display.

A screening trial in 1992/93 tested 13 foliar-acting herbicides on pot-grown plants at Long Ashton Research Station and in the field. It highlighted the potential of Arsenal (imazapyr), Ally (metsulfuron-methyl), Dow Shield (clopyralid) and Quantum (tribenuron-methyl). All went into trials on Manor Farm.

Arsenal and Ally (with wetter) did best, both outperforming Roundup for eradicating well-established OMB from a fence line. The treatments were sprayed on to one side only in August 1994. By this summer the "Roundupped" areas contained a lot of re-growth, especially from the unsprayed side.

Another trial this year tested Arsenal at two doses in a badly infested ancient parish boundary hedge. Treatment in spring or summer followed manual clearance of most of the vegetation.

"The late March treatment seems to have been very effective, especially at the higher dose," says Mr Clay.

Despite the apparent success, he warns it is too soon to claim eradication. "The key question is how soon can we replant?"

Having spent "several £1000s" over the past three years, the Grasshoppers want official recognition of their initial research. "It now needs a better-funded and more broadly-based organisation to take it up," says Mr Harper. Without more effort much grant cash could be wasted, he says.