Kites, canons, predatory birds and Mylar tape all have one thing in common: they are used by growers in an often futile attempt to scare away birds. However, the birds only get used to them in time. Experts agree the only sure and humane method is exclusion. This is where bird netting comes in.
"As far as I'm concerned bird netting is the only thing that works," said Glen McGourty, University of California winegrowing advisor in Mendocino and Lake counties. "These bird-scaring devices just annoy your neighbors."
Around the world, increasing numbers of vineyard growers are netting their vineyards. Twenty years ago a typical California trellis system consisted of sprawling canopies that hid the fruit; nowadays, the popular vertical shoot position is a bonanza for both the wine industry and birds. These trellis systems may translate to positive benefits in terms of airflow and filtered light penetration, but also make the fruit more visible and attractive to foraging birds.
Higher populations of birds will generally be found in (1) urban areas where birds thrive on garbage or other food, (2) nearby forests and woodlands that provide habitat for birds, or (3) animal production sites, such as farms and dairies
"The biggest problem at Cal Poly is from our school's dairy operations," said Keith Patterson, professor of viticulture at California State University Cal-Poly San Luis Obispo. "The sky is just black with flocks of birds 50,000 strong, and they can pick my little vineyard clean in a couple of days."
It's hard to project with certainty who is going to have a bird problem, Patterson says. Besides proximity to urban areas and animal operations, there are other signs of bird habitation and congregation. If Patterson finds himself parked in front of a vineyard that is surrounded by oak trees or with lots of power lines overhead or near wooded areas, this often means birds are nearby.
Larry Smyth, owner of Carriage Vineyards, south of Paso Robles, says his location near a wooded area is definitely a high bird area. He says netting is the only thing that works for him; his 27 acres calls for 22 miles of net.
In Sonoma County, Rhonda Smith, viticulture UC farm advisor for the University of California Cooperative Extension sees the need for netting as an individual determination, noting that the shiny Mylar tape and kites may be somewhat effective in low-pressure situations. In general, she mostly finds growers netting in small vineyards abutting trees and wooded areas. "In the vast majority of areas, you don't usually need bird protection if you have large, open, flat areas, such as in Dry Creek or Alexander Valley," she said. However, some large valleys may be along the migratory path of bird flocks looking for food for their journey.
Steve Tillmann, who directs field research and development for Minnesota-based Plantra, Inc., makers of Bare Hand™ Bird Nets, says there are numerous growers who net large vineyards. He said there are several operations in the North Coast area alone netting thousands of acres; one grower in Santa Barbara County has 600 acres of netted vineyard.
Bunch Rot Avoidance
The types of problems caused by birds are two-fold. In some areas, without netting there would be no crop to speak of. Gregarious birds that fly in large flocks can strip a small vineyard in a day. Tillmann says it's not just about the missing berries, which alone can cause significant economic loss; protecing grape flavor and the impact on wine quality, he says, is really the bigger issue. The focus used to be on the grapes the birds took, but today, in the face of growing market pressure to deliver quality, more attention is being paid to the damage the birds leave behind.
Historically growers have looked at bird netting to protect the crop from being physically taken away. However, many bird species such as starlings and finches (or linnets) are too small to actually take the whole grape, so they just peck at the fruit. Their sharp feet pierce the berries. This sets up a whole process of fungal infections, degradations, rot and off-flavors in the wine, and fruit flies attracted to that oozing juice spread the bacteria around to other berries. Yellow jackets, which are hazardous to the pickers, also may be attracted.
Once the crop is harvested, undesirable fruit is mixed with intact fruit, and the bacteria is spread. From this standpoint, netting is absolutely worth the cost, Patterson says.
"It doesn't take many of those grapes to ruin a whole lot," he said. "Basically you are just inoculating the entire bin with bad grapes. Wineries will look for that; and if they see a whole lot of damage, they could reject the lot."
According to Patterson, a consistent flavor that customers can count on may be absent in the face of Volatile Acidity issues. It is hard enough to produce a similar wine from a particular vineyard's varietal without adding an off-flavor.
Keith Striegler, director of the new Continental Climate Viticulture and Enology Center at University of Missouri in Columbia, agrees that the bigger issue from bird feeding is the bunch rot.
"Bird netting has become the standard cultural practice for us in Missouri, especially for high-value grapes," he said. "A lot of growers are doing it more and more; maybe not every vineyard but I certainly do it for my research plots."
Striegler, formerly with the Viticulture and Enology Research Center in Fresno, California, says in cooler climates, such as the Midwest or California's northern winegrowing areas, the main culprit is bunch rot. Then if you have a little rain, you can get sour rot on top of that. Whichever type of rot grapes have, it's always a bad thing, Striegler says.
As more and more growers go to mechanical harvesting, removing "bad" grapes is nearly impossible. Even with hand-picking, sending crews into vineyards to drop the bad grapes is a very expensive operation; workers paid by harvest weight would be loath to drop crop. The best solution is to stop rot before it happens and not put quality wine at risk.
Susceptible varieties
Certain varieties are more susceptible to bunch rot, and should be watched and protected carefully, Striegler said. "Vignoles is a very, very popular wine back here in the Midwest, but it is a tight-clustered variety and is more susceptible to bunch rot."
Some California-grown winegrape varieties with bunch rot susceptibility are Pinot Noir, Chardonnay, Riesling, Chenin Blanc and Zinfandel.
McGourty says he sees variety preference. At an experimental vineyard he runs with 46 Mediterranean varietals, birds turned out to be connoisseurs with a marked preference. Because McGourty had a randomized experimental design, he was able to observe that the birds particularly liked Pinot Gris, possibly because they were first to ripen. "They would just fly down and clean out the berries in a day," he said. "In our region, starlings are probably the worst."
Proper timing is critical
Typically, the netting is applied right at veraison or four to six weeks before harvest. Timing is important, said Patterson. "You have to get the netting out at the very first sign of any color. That's what attracts birds."
Patterson says once the birds realize that grapes are ready and have a taste of the fruit, they will try just about anything to get at the fruit, even with netting. Some growers tie the netting up at the bottom with simple twists that are easily removed. Others use light staples that come off easily.
"In a perfect world, a grapevine stops growing at veraison," Patterson said. "That may be hard to do on a high-vigor site. In some cases it doesn't matter what you do, the growth is not being controlled."
Applying netting at veraison makes staying on top of all the vineyard operations especially crucial, says Striegler. Once the netting is on, you don't really want to remove it until right before harvest so birds have absolutely no chance to feast on berries. Fungicide sprays can also be applied with the netting in place. Removal is fairly simple with specialized equipment available from dealers, or in some cases fabricated or adapted using existing pull implements.
Small investment for
big relief
Some people complain about the price of netting, but Tillmann says prices are exaggerated. The cost can be amortized and depreciated over the lifespan of the netting and can work out to less than $300 per acre per season for single-row applications. This estimate includes purchase of netting, application and removal labor and use of a tractor. Not included is the cost of specialized apparatus to apply the netting. A simple netting applicator, supported by a three-point hitch, can be purchased for as low as $1,000 or less.
In the Central Coast region of California where growers are getting $1,000 to $1,500 and more a ton for quality winegrapes, it certainly pencils out, especially in a situation with bird pressures. In other areas, particularly in the bird-prone North Coast, where growers get upwards of $3,000 per ton or more, one doesn't even need the pencil to immediately find the worth.
Multi-row and selective netting
In Australia, where it is standard to find the whole vineyard netted, multi-row netting is common practice. This can save quite a bit of money, Tillmann says, by slashing labor and material costs and significantly reducing the required investment compared to netting one row at a time.
Simon Graves, with Southcorp Wines in Paso Robles, says he can drive his ATV down his dual row vineyard. "I would like to do three or four rows at once rather than two. The problems are just getting the net wide enough, though you can custom order your netting."
You may not have to do the whole vineyard, McGourty says. If your problem is spotty or localized, he says, you may just want to concentrate on the first few rows near power lines, trees and brushy areas. Patterson noticed in Sonoma County that some people are just using a three-foot strip of netting across the side of the vines where the clusters are. "When you want to pack it up, you just take that netting and tie it to your lower wire," he says. wbm
Bird Netting Suppliers
Company Location Phone Website
Bird-B-Gone, Inc. Mission Viejo, CA 800-392-6915 www.birdbgone.com
Bird-X, Inc. Chicago, IL 312-226-2473 www.bird-x.com
Nixalite East Moline, IL 888-624-1189 www.nixalite.com
Plantra, Inc. Atascadero, CA 805-462-2767 www.plantra.com
Spec Trellising Ivyland, PA 800-237-4594 www.spectrellising.com
Sutton AG Enterprises, Inc. Salinas, CA 866-280-6229 www.suttonag.com
Melinda Warner is a freelance writer based in Fresno and a former editor of Grapegrower.
