Hidden infestation: Why the American grapevine leafhopper threatens viticulture

The American leafhopper sucks on grapevines. This alone does not harm the plants. However, in doing so, they absorb and spread the pathogens that cause Flavescence doreé. Photo: Gernot Kunz

The spread of the American grapevine leafhopper is making headlines in Styria. The concerns of winegrowers are justified, says University of Graz biologist Gernot Kunz.

More and more vines in Styria are affected by Flavescence dorée. The leaves change colour and curl, the berries shrivel and do not ripen. "The only way to combat the disease is to grub the vines up," confirms biologist Gernot Kunz. The bacterial infection is spread exclusively by the American grapevine leafhopper, which is currently spreading in our region. "The animals pick up the pathogens when they suck on an infected vine and infect other vines after an incubation period of three to four weeks," explains the researcher. The tricky thing is that plants can carry the disease years before they show symptoms. The extent of the impending epidemic is therefore still difficult to estimate.

Old acquaintances
The five to six millimetre long leafhoppers are not new to Styria. They were already detected in Klöch in 2004. "It took around ten years for the first damage to occur there," reports Kunz. The biologist first spotted the animal in Graz in 2019. "The high density of individuals in private gardens and abandoned vineyards is definitely a problem here," he warns.

Remedy
Countermeasures exist, but are limited: "With expertise, the adults can be attracted and removed by artificial light sources on warm summer nights," the researcher explains. However, as the insects can cover long distances in flight, they keep coming back.

Dagmar Eklaude

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