Issue link: http://read.dmtmag.com/i/72545
VINEYARD By Gregory A. Giusti, UCC Extension ird damage in wine grape vineyards is a worldwide problem. The species of birds or the variety of grapes may be different, but the result is the same regardless of whether you're growing grapes in California, Ontar- io, France, Italy or Greece. Birds eat grapes. Starting in the late 1960s and '70s, the scientific literature begins to address in earnest the problems reported by growers who were fac- ing increasing bird damage in their vineyards. In those early papers the authors wrote how "the indus- try" was changing from Vitis labrusca stock to V. vinifera, and the varieties they were working with had names such as Concord, Seibel and ruby cabernet. Much of the work involved attempting to identify whether different varieties were more attractive to birds than others. As the work evolved, the empha- sis changed to focus on developing, testing and registering "bird repel- lents" as a means to lessen over- all damage. As was the mode du jour, people naturally considered a chemical solution to the problem. Extensive testing focused on devel- oping a spray-on, chemical taste 54 VINEYARD & WINERY MANAGEMENT JULY - AUG 2012 aversion to minimize palatability of grapes to birds. The active ingredient Methio- carb was known by the trade name Mesurol and was eventually reg- istered for cherries, bush berries, grapes and artichokes (for snail and slug control). The product persist- ed through most of the 1980s, but eventually lost its registration due to changes in chemical registration requirements and associated costs. Wine grape growers (at least in California) were always a bit skep- tical about putting a "taste aver- sion" on their fruit for fear that it would affect the final product and thereby cause an aversion to their wines. Since this time, most work on reducing bird damage to wine grapes has focused on non-chemi- cal products. WHO ARE THE CULPRITS? A number of bird species have been reported in scientific literature as having an affinity for eating wine grapes. In North America, in order of importance, the most commonly cited bird pests are: the European starling, American robin, house finch (linnet), cedar waxwing and American goldfinch. In my own vineyard I have personally observed Western bluebirds, California quail and mockingbirds feeding aggres- sively on the ripening fruit. There is a 1973 report that examined the feeding behavior among the most common pest spe- cies. Not surprisingly, the results showed that the larger bird spe- cies (European starling) ate more grapes than the smaller one (house finch). However, the study went on to report how species' flocking behavior affects the overall damage caused by one species over anoth- er. In other words, even though a robin may eat more berries per foraging event than a house finch, chances are good that there will be far more house finches in a par- ticular vineyard, since they tend to aggregate in flocks, while robins are more solitary in their behav- ior. Likewise, though robins and starlings are about the same size, starling flocking behavior may have hundreds of birds descending in a vineyard, causing far more damage than the more sparsely distributed robins. ASSESSING DAMAGE Leave it to some "bird nerd" to articulate the type of damage inflicted by different species of AT A GLANCE Bird damage is a problem in vine- yards all over the world. In North America, the most com- mon bird pests are European star- lings, American robins and house finches. The flocking patterns of bird spe- cies will impact the amount of damage they inflict. Diligent record keeping can help growers determine the damage- reduction method that works best for their situation. WWW.VWM-ONLINE.COM