To net or not to net: bird netting is aggravating but effective; what growers should look for.
So why does any grapegrower bother? The answer in two words: Netting works.
Given that netting in any form is an extra vineyard expense, in what areas are growers most likely to need this form of protection? And if you do decide to net, what factors should you consider?
Bird behavior and habitat
Large, flat vineyards may not have any pressure from birds if they have no nearby woodlands or places where birds have access to shelter and food. In the East, however, many vineyards are adjacent to woods, and other types of farms may be close by. Growers located closer to suburban residences may have neighbors with bushes, trees and gardens that provide cover, and backyard birdfeeders that encourage birds to set up residence.
A major problem can be flight paths of migratory birds, generations of which have flown over the same land--long before the current owner planted grapes. In some parts of the country, the timing of migratory patterns may be changing: As the weather becomes warmer farther north for longer periods, birds migrate south on a different time schedule. Those changes may not be huge, but if a flock of birds used to pass through before grapes were ripe, and now arrives just as grapes are at their peak of ripeness, the result may be a significant loss of or damage to the grape crop.
Before looking into the possibilities for netting, a vineyard owner should determine the kind(s) of birds that are likely to be a problem. The size of the holes in the netting will not be as much of an issue if the birds landing in a vineyard are large, such as crows. However, if the birds are small, the size of the holes could be a significant factor.
There are other issues to consider before buying bird netting. Mary Jo Thaden, owner of MDT and Associates in Minneapolis, Minn., has sold vineyard supplies to growers in the East and Midwest for more than 20 years. Her first words of advice about bird control were: "If you're feeding birds at your vineyard, stop. This only encourages birds to stick around and ultimately eat your grapes."
She also tells vineyard managers to remove any nests they find tucked into the vines when they go through their vineyards in the springtime. And there should definitely not be any birdhouses in a vineyard or nearby.
Types of netting
Netting comes in many widths, lengths and types of construction. The first decision a grower must make is whether to use a net that drapes over one or multiple rows, covers only the sides of a row or creates a canopy or "roof" of net over the entire vineyard.
Over the Row Netting: The traditional netting used in the United States drapes over a row of vines or multiple rows, depending on the width of the netting. Made of extruded black plastic or woven mesh, it's difficult to apply. While protecting the grapes for weeks, leaves, tendrils and vines work their way into the mesh; consequently, removing the netting at the end of a season is even more difficult.
Side Netting: Nets that cover only the fruiting zone part of the vine have been very popular in Australia and New Zealand, and they are increasingly being used in eastern regions of the U.S. These nets have the advantage of not being as wide or cumbersome to apply, and they're not quite as expensive as the netting required to cover the entire row. Some side netting can be rolled up on a wire and left year-round in the vineyard. Michael Schmidt of Spec Trellising in lvyland, Penn., was quick to point out that it is important to fasten the netting both above and underneath the fruiting zone--otherwise the birds will figure out how to get into the grapes in spite of the net.
Overhead Netting: Full canopy overhead nets are a new way to protect a vineyard. One company that makes this type of netting is Smart Net Systems in British Columbia, Canada. In this system, an additional wire is strung from post to post down the row of vines, and the net rests like a roof on top of the wires. In a new vineyard, longer posts can be installed to carry the wire and the netting 12 or more inches above the vines. If an established vineyard is being retrofitted for this type of netting, extenders can be added to posts so the wire is about 8 feet from the ground, or 12 inches above the vines.
One of the advantages of this type of netting is that the net can be raised at the end of the rows, and a tractor or truck can be driven into the vineyard underneath the canopy. The grower can mow, apply sprays, harvest grapes or remove lugs without touching the netting over the vines.
Gary Mount, owner of Terhune Orchards in Princeton, N.J., installed overhead netting from Smart Net Systems during summer 2009. He told Wine East that he installed overhead netting on his 4.5-acre vineyard because the bird distress call system he used the year before did not keep crows from taking half his crop. "I don't have good tolerance for animals or birds taking what we grow," Mount said. "This is what we have to do, because it works."
Each net is 54 feet wide and 500 feet long. A cord is threaded through the side edges to facilitate threading onto support wires, and when the nets are in place, the sides are clipped together to secure them. "Our biggest problem in the installation was that we didn't know how tight to pull the net to get it to lie flat," Mount reported. "So before we rolled it back after harvest, we marked where each post was with a piece of colored yarn. Next summer when we slide it out over the wires, we'll know exactly where the net should be."
Factors to consider
Denier is the thickness of the monofilament, or yarn, used to knit and knot the net. Its range is usually between 410 and 540; many of the nets are about 500 denier.
Weight of a net depends partly on the denier and partly on the number of stitches per square meter or net. The more stitches, the heavier the net. Extruded black plastic net is usually lighter than woven nets.
Size and shape of the holes can affect the net's strength and also which birds are kept away from the grapes. Square holes have one stitch at each corner; hexagonal holes have three stitches per side. Some nets have a triangular hole and can have much smaller hole sizes. For example, Schmidt at Spec Trellising sells one net with triangular holes measuring only 10 mm x 4 mm. Knitted nets are usually not recommended, because they can unravel when cut or snagged.
Shading--Color is a factor that affects the shading created by netting. White nets have approximately 8% shading, green nets 12% and black nets 14%. Since they provide less shading, white nets facilitate faster ripening.
Type of Material--Nets made of black extruded plastic are more rigid and weigh less than other nets. They also have sharper edges and are more likely cut those applying or removing them. White woven nets are more flexible. They can be stretched wider or longer. Growers say that birds are able to see white and are frightened away when the white nets flap in a breeze.
There is no one best way to apply netting. Installation depends partly on the type of netting, with side netting on short rows being the easiest. Over-the-row netting can be applied from a spindle mounted on a tractor--or by using other pieces of equipment available on the farm.
Another factor is cost. Manual applicators can cost as little as $200, while fully automatic machines can cost $7,000 or more. Applicators made in Europe fluctuate in price depending on the strength or weakness of the dollar.
Corn detassler = net applicator
Keith Mckinney, owner of Clear Creek Vineyard in Colo, lowa, has 3 acres of grapes, but like many farmers in lowa, he also grows corn and soybeans. His solution to the bird problem in his vineyard was to turn to another piece of farm equipment: a corn-detassling machine that was built to straddle cornstalks. "Our trellis is 6-feet high, so we took an old corn detassler, which is a tall machine, and made it even taller." Soybean reels hold the 14-foot-wide netting, and a hydraulic motor rolls the netting back onto the reel.
"We have to have two people on either side of the row when we reroll the net," Mckinney explained. "That's harder to do than to apply it." It takes him a couple of hours per acre to apply the netting, a task that happens just after veraison.
Another netting machine was invented in lowa by two brothers, David and Paul Klodd. David Klodd is the winemaker at Summerset Winery in Indianola, and has a 12-acre vineyard with his wife Heidi. Paul Klodd is a dentist who also owns a metal fabrication company. Three years ago, David Klodd designed the "Nettergetter" machine in an act of desperation. He reported to Wine East: "Never in my life has anything made me so angry. Even Mother Teresa would get angry if she had to remove black plastic netting off of grapevines."
He told Ron Marks, owner of Summerset Winery, that he and his brother would make a machine to apply and remove bird netting more easily. The deal was, if it worked, Marks had to buy one for his vineyard. "I had an idea to make the reel work like a fishing reel. The problem was in getting the ratios right for the gears." Paul Klodd helped with the engineering and production of the machine.
"The first time we took it into the vineyard at Summerset, it was raining," Klodd remembered. "That turned out not to be a problem. The machine was mounted on a skid loader, and it worked so well I had to slow the loader down, it went so fast. Ron watched, then went back into the winery and wrote me a check."
The Nettergetter works quickly and efficiently, and it allows Klodd to apply netting when and where it is needed. "You don't want to put netting on too early or too late. This machine is both time- and money-saving, because we can apply the netting to an early ripening grape, then remove the netting and put it onto a later variety."
The Klodd brothers now manufacture three versions of the Nettergetter: manual, semi-automatic and fully automatic. All three are built on the same jig and, as a result, it is possible for a grower to purchase a manual version and several years later return it to be upgraded to an automatic machine. It can be mounted on a skid loader or a tractor, and requires one person to drive and two others to walk behind the machine to check for centering and proper draping of the netting material. The machine will apply or remove both extruded black plastic netting and woven netting.
According to Klodd, netting can last for years, depending on the quality of the net and how well the grower takes care of it. In winter, he stores his miles of netting on spools stacked in a barn. When the robins, blackbirds and starlings start to show up, he's ready for them. In the meantime, the Klodd brothers have sold Nettergetters in lowa, many surrounding states and as far away as Oregon.
Smart Net Systems sells a machine, the NetWizz Std Auto Tension, which will apply and remove bird netting in medium to large vineyards or orchards. However, since growers can slide Smart Net's overhead netting to the end of the rows and cover it for the winter, expensive machinery is not needed to remove and then reinstall the nets.
RELATED ARTICLE: Ways to extend the life of your netting
* Use post covers.
* Avoid foliage clips that can snag the netting.
* Pay attention and use great care when removing nets; Mary Jo Thaden of MDT and Associates points out that "netting always comes off second best in tugs-of-war between posts and tractors."
* Store the netting appropriately. It probably won't go back into the bag it came out of. Thaden suggests using barrels or "bean" bags (as in soybean bags with handles that measure 35 x 35 x 40 inches).
* Make sure mice can't set up housekeeping in your nets during the winter. They can reduce the lifespan of netting quickly.
Wine East HIGHLIGHTS:
* Netting is a solution that works for problems with birds in the vineyard.
* Netting can cover only the fruit zone, drape over a row of vines, or create an overhead roof.
* Net applicators come in a wide price range, from $200 to $7,000.
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|Comment:||To net or not to net: bird netting is aggravating but effective; what growers should look for.(Grapegrowing)|
|Author:||McKee, Linda Jones|
|Publication:||Wines & Vines|
|Date:||Mar 1, 2010|
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