Root Borers a Danger to Grapes in the Southeast

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University of Georgia Extension/Pictured is a grape root borer.

By Clint Thompson

The time is now for grape producers to protect their crop against the grape root borer, said Brett Blaauw, assistant professor in the Department of Entomology at the University of Georgia. He said usually in north Georgia, the grape root borers will emerge in early July.

According to the UGA Extension Viticulture Blog, if farmers have not deployed their pheromone dispensers as part of the mating disruption tactic, it is time to get those distributed.

University of Georgia Extension/Pictured is a grape root borer monitoring trap.

“Our mating disruption is probably our best option. That’s using a pheromone that basically confuses the male moths. It blocks them from finding the female moths so they can’t mate. No mating, no mates, no eggs, no larvae and then, hopefully, no disruption of the roots,” Blaauw said. “But because of its two-year life cycle, it takes a least two years for the mating disruption to start to show that it’s working in a vineyard. That can be tough because when you use something management you want to see it working right away. But the main disruption takes a couple of years to see any benefit.”

What Impact Does Grape Root Borers Have?

As the name implies, the grape root borer larvae feed on the roots. Blaauw said they have a two-year life cycle and will feed underground on the roots for almost 22 months. Unfortunately, it is out of sight, out of mind for many grape producers. Being underground, the borers go unnoticed until the vine begins to deteriorate.

“Previous research has shown that by having these larvae feeding on the roots it can reduce the vine’s yields by 50%. That’s just having one larvae,” Blaauw said. “The mature larvae are almost an inch long so they’re pretty good size larvae, a little bit like root boring caterpillars feeding for two years. Just having one can reduce yield by 50%. If you have more than one feeding on a vine, that could easily significantly reduce the survivability of the vine; it can reduce the fruit quality and eventually lead to vine death.

“Growing fruit in the Southeast is tough enough with diseases and other insects. Growing grapes is really tough. Grape vines, at least the vonifera type grapes are often subject to different diseases. One is Pierce’s Disease. Pierce’s Disease can take down vines pretty quickly, too. A lot of growers, when they have a vine that dies, they kind of assume it’s due to a disease. They’re not usually thinking about grape root borer just because it’s underground. You don’t really see what’s going on until you pull that vine out and see the roots all chewed up. Then it’s obviously too late.”

Effective Management Tool

Another effective way to manage grape root borers is to suppress the weeds under the vines. This can significantly reduce the success rate of the eggs hatching and the larvae making it to the roots. If weeds are present, they serve as protective barriers for the little caterpillars. They protect them from the sun and protect them from other insects that are going to be feeding on them.

“If you get rid of those weeds, you create a pretty harsh environment. Bare soil is not a good place for an insect, especially if you’re a tiny little caterpillar,” Blaauw said.