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Vineyard manager uses bluebirds to control blue-green sharpshooters
A female and a male bluebird are in a nest-building mode atop a birdhouse at Spring Mountain Vineyards. The growth in bluebird population at Spring Mountain over the past year has been consistent with the decline of blue-green sharpshooters. Bob Minenna photo

If you build it they will come — or words to that effect — is what a friend told Spring Mountain Vineyards Manager Ron Rosenbrand a year ago.

The friend was “Amigo Bob” Cantisano, a sage of organic farming, and he wasn’t talking about laying out a baseball diamond in the middle of an Iowa cornfield to attract the ghosts of Shoeless Joe Jackson and Ty Cobb, et al. Cantisano was talking about building birdhouses to attract bluebirds to the Spring Mountain vineyards to combat the blue-green sharpshooter, which, as a smaller cousin to the more notorious glassy winged sharpshooter, is sometimes called “the wine bug.” Sharpshooters spread Pierce’s disease, which dehydrates the vines and kills them within two or three years.

What Cantisano told him, Rosenbrand recalls, was that there isn’t a good natural insect predator to attack the sharpshooters, but he might try bluebirds.

“I said, ‘OK, that sounds great, but where do I buy bluebirds?’ He said, ‘You don’t buy them — you just build houses for them and they will come,’” said Rosenbrand.

Bluebirds work

One year and 500 birdhouses later, Rosenbrand said, the results are growing ever more conclusive in Spring Mountain’s 135 vineyard blocks that the bluebirds really work.

“Bluebirds are our best friends when it comes to clearing out the sharpshooters,” he said.

Rosenbrand began the bluebird experiment a year ago this month. By summer he had put up 300 houses.

“When we first put them up, the bluebirds started using them and nesting,” he said. “By summer they were all over the property and reproducing.”

The decline in population of the sharpshooters has been consistent with the spike in the number of bluebirds.

“In April last year we saw quite a few sharpshooters,” Rosenbrand said. “When the bluebirds started coming we were monitoring all our charts and in July found almost no sharpshooters. That’s traditionally a time when you find 50 to 100 per plot.

“It was just amazing to me to think that the bluebirds did that much,” he added. “I’m really interested in going through this spring to see what happens because I don’t honestly know if it was the bluebirds; it could have been something else.”

He expects to get conclusive data by the end of this month.

The beauty of the bluebird houses is that the entryways are so small that only one other bird — swallows, also believed to attack sharpshooters — are known to use them. Bluebirds won’t have it any other way, and, in fact, won’t nest in birdhouses with entryways large enough to accommodate other birds.

In the total build-out, the houses are spaced about 100 feet apart, “because when bluebirds are nesting they tend to fight with one another when they’re too close together,” Rosenbrand said.

Temecula lesson

The damage sharpshooters are capable of wreaking on vineyards cannot be taken lightly. A decade ago they wiped out a large number of vineyards near the town of Temecula in Southern California.

“We learned a lesson that Temecula taught everybody,” said Rosenbrand. “You need to control (sharpshooters) as soon as you start seeing them.”

A negative experience with spraying a few years ago prompted Rosenbrand to become a devotee of the biocontrol of insects.

“We had to sign a compliance agreement with the Ag Commissioner’s office to use certain chemicals and treatments that would control the vine mealy bug,” he said. “I sprayed everything they told me to spray, which were really tough insecticides. I was worried for myself, worried for my employees and for my neighbors, because we were spraying stuff that was really toxic and after three years my mealy bug problem was worse than it was when we started.”

Since then, Rosenbrand has used parasitic wasps, predator mites and cryptolaemus (beetles) to effectively control invading insects. But never, until now, birds.

“I don’t know how many other people are into bluebirds for pest control,” he said, “but I do think it has promising aspects. We’re excited about our results so far. It’s something that will help us get totally away from insecticides.”

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