Winemakers in Australia's Clare valley are facing disaster with the imminent arrival of locust swarms, which could destroy the entire crop, according to industry leaders.

Locusts were reported as far south as Robertson, near Burra, yesterday, and according to Australian reports, depending on the wind could reach Clare Valley within days.

A spokesman for the Clare Valley Winemakers Association, Andrew Hardy, said the "worst case" scenario was that the entire grape crop could be lost - some 25,000 tonnes potentially worth $260m.

However, the danger is lessened by the relative maturity of most of the crop, with clusters of grapes already beginning to form.

"If they came earlier, it probably would have been worse but that worst case scenario still looms over us," said Hardy.

He hoped that government spraying programmes further north had significantly thinned the swarms and that the green grass and weeds on the ground might prove more attractive to the locust.

The threat of the locust is also a worry for winemakers averse to using pesticides. The fear is that spraying would also kill off beneficial predators such as lacewings and ladybirds, which protect vines from the serious threat of light-brown apple moths.

John Barry, vineyard manager for Jim Barry Wines said he would wait and see the extent of any initial damage before deciding whether to spray.

Barry said: "It's a waiting game. If the locusts are causing damage I will have to use these chemicals even though it will wipe out a couple of beneficiaries as well. It will not be the first time locusts have reached the valley but the huge numbers in the present swarms mean the potential for damage is much greater."