A mystery bug targeting Semillon and Sauvignon Blanc grapes around Margaret River is being investigated by Australia’s Department of Food and Agriculture, the West Australian reports.
Scientists said they had seen what appears to be a generic “looper bug” on grapevines, which they say has affected up to 15 percent of vineyards in the region.
Stella Bella Wines vineyard operations manager Peter Wood said he had lost nearly a block of Sauvignon Blanc grapes.
“I think they live in the eucalypt forests, and because of the unseasonal November and December, they’ve come out into the vines,” he said, noting reports that the bugs had hit mainly white varieties.
Department entomologist Stewart Learmonth said he had about 15 phone calls in December and early January about the bug, which chewed through grapes and left vines vulnerable to conditions such as botrytis and berry-rot.
The grub has also been known to attack apple crops, with reports of fruit damage in areas around Manjimup last November.
“I was surprised. We’d never had reports of it in vineyards before, but we want to get it identified,” he said.
Learmonth said his impression was the bug was native, rather than introduced, but he dismissed assertions it originated in eucalyptus forests.
“We don’t know what it feeds on, but it’s unlikely to be eucalypt,” he said. “We don’t know what it is — looper is its generic name — and we’re sending it off so we can identify it and look up the literature.”
Learmonth said the bug had affected vineyards around Margaret River, from Busselton to Yallingup, and added that Sauvignon Blanc and Semillon grapes were not the only varieties impacted.
“People have seen it on all varieties. It could affect yields and the quality of grapes if it promotes disease,” he said.
Margaret River Wine Industry Association President Leah Clearwater said there was widespread concern over the looper bugs in the lead-up to grape harvest in the next few months.
Early spraying with Avatar insecticide had killed the bugs, but spraying had to be stopped as bunches matured.
“I’ve seen them in quite a number of vineyards, and initially we weren’t too concerned because they were feeding on shot berries — that is, berries which haven’t fertilized — so we saw it as a blessing,” Clearwater said.
“But if we can’t control it, there could be significant crop losses.”