An insect with the potential to destroy vine harvests is spreading in western and southern Switzerland.

The yellow leafhopper (Scaphoideus titanus) was observed in 2008 for the first time in the central part of the southern canton of Valais and at the western end of Lake Geneva, the Agroscope agricultural research station said on Friday.

It was already entrenched in the southeastern canton of Ticino, canton Geneva and along the northern edge of Lake Geneva.

In itself the insect is harmless, but if it feeds on a plant suffering from the "grapevine yellows" disease, it can spread the bacteria in epidemic proportions.

The infection, also known as flavescence dorée, can kill young plants and greatly reduce the productivity of older ones. In infected plants the flowers and fruit clusters shrivel up and drop off. Since there is no known way to eradicate it, efforts are focussed on getting rid of the leafhopper which is its vector.

Ticino is so far the only area where both the disease and the insect have been found. But chemical treatment of all vine nurseries has been made compulsory to halt the further spread of the insect.

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