The cultivation of grapes often leads to a compromised harvest due to local wildlife. Grapes are highly attractive to animals because of their high sugar content and thin skin, especially as they begin to ripen. Protecting a crop requires a strategic, multi-layered approach that considers the specific pests in the growing environment. Successful grape protection relies on combining physical exclusion, sensory deterrence, and proactive site management.
Implementing Physical Barriers
Physical barriers are the most reliable method for preventing wildlife damage because they completely exclude animals from the fruit. Bird netting is the primary defense against the most common grape pest. Mesh sizes typically range from 10 to 20 millimeters to block small birds like starlings and sparrows. For protection against tiny insects like the spotted-wing drosophila, a much finer mesh of 1 to 5 millimeters is necessary.
The netting should be installed around the time the grapes begin to change color (veraison) and secured at the bottom to prevent ground animals from crawling underneath.
For high-value or smaller operations, individual bunch protection is a highly effective solution. This involves covering clusters with small organza or paper bags. These bags have a fine mesh that allows for air circulation and light penetration while physically blocking insects and birds.
A perimeter fence is necessary to deter large mammals, particularly deer. Non-electrified fencing should be at least eight feet tall to be effective against deer.
An electrified high-tensile fence serves as a psychological barrier for persistent large pests. A fence charged to between 4,000 and 5,000 volts can be made more effective by baiting the wire with peanut butter or molasses. This encourages the deer to touch the wire, delivering a memorable shock that conditions the animal to avoid the area permanently.
Non-Lethal Deterrent Methods
Deterrents appeal to an animal’s senses to discourage them from approaching the vineyard. Visual deterrents, such as reflective Mylar tape or shiny balloons, flash and move in the wind, creating a disorienting effect. The effectiveness of these tools relies on their novelty, so they should be moved frequently to prevent animals from becoming accustomed to their presence.
Auditory deterrents, like motion-activated sprinklers, are effective against deer and raccoons. The sudden burst of water and noise causes a startling sensory shock. These devices use infrared sensors to detect an animal’s heat and movement. While sonic devices that emit high-frequency sounds are available, their long-term effectiveness is limited because animals quickly habituate to the noise.
Repellents that target taste or smell require regular reapplication, especially after rain or irrigation. Repellents containing capsaicin make the grapes taste unpleasant to animals. Predator urine scents can also be used to create the illusion that a natural enemy is nearby, providing a temporary deterrent.
Site Management and Pest Identification
Properly identifying the pest causing the damage is the first step in selecting the most effective protection strategy.
Pest Identification
Damage from deer often appears as ragged breaks on canes and stems because they lack upper incisor teeth. Birds leave scattered, small peck marks on the fruit. Raccoons tend to be more destructive, often stripping the husks from the cluster and knocking down canes. Squirrels leave behind scattered pieces of fruit after eating only the heart.
Sanitation
Sanitation reduces the appeal of the vineyard to ground pests. Fallen fruit and other organic debris should be removed promptly, as fermenting sugars attract pests and can lead to secondary problems like disease. Removing these food sources reduces the likelihood of an infestation becoming established.
Canopy Management
Canopy management techniques, such as pruning and leaf removal, play a significant role in pest control by making the fruit less accessible. Removing leaves around the fruiting zone improves air circulation, which reduces humidity and lowers the risk of fungal diseases. A less dense canopy also makes it more difficult for birds to hide and access the clusters.
Alternative Hydration
In dry periods, grapes can become a source of hydration for wildlife, which will puncture the fruit to access the juice. Providing alternative water sources, such as a shallow water trough or a birdbath placed away from the vines, can divert animals seeking water. These water stations should be kept clean and shallow to prevent the drowning of smaller wildlife and to discourage the growth of bacteria and mosquitoes.