PENTICTON - Okanagan grape growers are monitoring their vineyards closely as a late-season pest makes a sudden appearance.
Growers aren’t sure why, but some valley vineyards are dealing with an influx of wasps as harvest gets underway.
Wasps pierce the skin of the berry and suck the juice from it, leaving a grape cluster that can develop bunch and sour rot that can spread from cluster to cluster. The two conditions result in poor quality fruit that has bitter, off flavours that are difficult for winemakers to deal with.
A larger than normal number of wasps are being seen in some vineyards, resulting in the need for extra vigilance and maintenance to keep the damage to a minimum. Protection methods include spraying to prevent rot and setting of pheromone traps for wasps in the vineyard.
Ezra Cipes with the Summerhill Pyramid Winery in Kelowna says their vineyard hasn’t experienced wasp damage this fall, but the winery draws grapes from other vineyards in the valley where Cipes says he has heard wasps are an issue.
Summerhill winemaker Michael Alexander agrees.
“We are seeing wasp damage. It happens. It’s not exclusively down south, but in many of our vineyards down south it’s more noticeable,” he says.
Alexander says the cause of the sudden influx of wasps is a bit of a mystery, perhaps the result of recent temperatures or wet weather experienced so far this September.
“We didn’t seem to have them for most of the year, just during harvest they’ve come out,” he says.
Alexander says vineyards are on the lookout for the problem and working around it if necessary.
“It’s been an interesting year, with the rain we’ve had, now wasps. Every year has its challenges,” he says.
In the South Okanagan, Blasted Church vineyards manager John Bailey says he’s seen what could be wasp or possibly bird damage in one block of his vineyard. He’s spoken with other vineyard managers who are finding varying degrees of wasp damage.
“What I’m finding is my wasp traps aren’t that full but I’m seeing a lot more small birds like finches and wrens in the canopy that don’t seem to be reacting to my bird deterrents,” he says.
He says birds attack grapevines in different ways, some taking the whole berry, while others suck the juice out, leaving damage similar to that of a wasp.
“It’s hard to say which is doing the damage. One grower I spoke to called it wasp damage,” Bailey says.
Tightrope Winery’s Graham O’Rourke says wasps haven’t been an issue at his vineyard, located on the Naramata bench.
“We’re into harvest and we’re not seeing it yet,” he says.
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