Batty Solution for Pierce's Disease?

A standard bat house occupied by Mexican free-tailed bats. PHOTO: R. Long

Mason, Texas -- While the world waits for a definitive answer to the Pierce's disease (PD) dilemma, Don Pullum of Akashic Vineyard in Mason, Texas thinks he has found at least part of the solution. Bats.

Mexican free-tailed bats, to be precise. "I have significantly fewer glassy- winged sharpshooters (GWSS) than anyone else in Mason County," he says. "Even though I don't weed aggressively, I don't use Admire, and I'm close to a creek, which means I have lots of potential."

Barbara French, the science officer at Bat Conservation International (BCI), likes the idea of using bats to control sharpshooters, but says there is no scientific proof it will work. "Bats are opportunistic eaters," French says. "They'll eat whatever bugs are available, about 2,000 mosquito-sized bugs per night. Orchards have been using bat houses for several years just for that reason." BCI is helping to get DNA tests on bat guano to see what the bats are actually eating.

A Mexican free-tailed bat in flight. PHOTO: Merlin D. Tuttle, BCI

Penny Adams, extension viticulture advisor for the Texas AgriLife Extension Service, says PD is currently affecting Texas vineyards in the north, south, east and central portions of the state. "So far, only West Texas and the High Plains are escaping the glassy-winged sharpshooter (the insect that carries PD), but they may be up there and not carrying PD and we aren't catching them because we aren't setting our traps at the right height," she says. "In fact, all of the southern U.S. from Florida to Anaheim is at risk."

Adams looked at Pullum's vineyard, and agrees that he has some risk factors, but feels that part of his success comes from not having many oak trees around. "We think the sharpshooters are wintering over in oak trees," she says. "Since Don doesn't have many, he starts out ahead."

Pullum disagrees. "There's another vineyard close to mine that has a more than 100-foot barrier all the way around, and he has a lot more sharpshooters than me."

Akashic Vineyard is an 8-acre farm in the northern part of the Texas Hill Country. Pullum is an inveterate experimenter, who likes to raise the more obscure grapes of Portugal, Spain, Southern France and Italy. He currently sells all he can grow, and serves as the winemaker for Sandstone Cellars.

"Batman" Don Pullum

His two bat houses are 20 feet in the air, placed back to back at the center of the vineyard. The total cost to put them up was $200. In his last census gathering--sitting on the hood of his truck with a glass of wine and a cigar--he counted 216 free-tail bats, and believes there are even more. Since each bat eats those 2,000 mosquito-sized insects every night, Pullum guesses the bats consume close to a half million bugs per night.

"I know we need to do more research on this before we can say my idea actually works," Pullum says. "But for $200, it's a pretty cheap experiment. Anyway, even if the bats aren't eating the sharpshooters, it's still cool to watch them come out at night."

The University of California Division of Agriculture and Natural Resources has recently published a useful 51-page guide, Songbird, Bat and Owl Boxes: Vineyard Management With an Eye Toward Wildlife. Many color illustrations, including the two reproduced here, are helpful for identifying, controlling and housing beneficial winged vineyard predators. Priced at $15 plus shipping and handling, the guide can be ordered at (800) 994-8849 or from anrcatalog.ucdavis.edu.