How to Manage Pests
UC Pest Management Guidelines
Several bird species including crowned sparrows, crows, European starlings, house finches, scrub jay, and yellow-billed magpies may cause substantial damage by feeding on ripening fruit. Crowned sparrows and house finches can also damage fruit buds during the dormant season. Bird damage usually is most severe in orchards that are adjacent to wild or brushy areas where birds find refuge, breeding sites, and other sources of food.
Regular weekly monitoring through bird counts will help you determine when damage actually starts so you can take action early. Watch for movement of birds into or within the orchard. This is particularly important for reducing damage to fruit buds as this damage is difficult to detect until bloom. Keep track of species by count and location seasonally if you have had substantial damage in the past. These records will help you plan control strategies in advance and will provide information on the effectiveness of previous control actions. As fruit begin to ripen, look for fruit that is damaged or has been knocked from the tree because this is another good technique for monitoring bird damage.
The most effective way to frighten birds from the orchard is to use a combination of noisemakers and visual repellents. For maximum effectiveness, rotate from one type of frightening device to another and do not use one combination of devices for more than a week; otherwise, birds will become used to it. Common noisemakers include roving patrols of bird bombs and shell crackers. Stationary devices such as gas cannons and electronic distress calls also provide relief. These stationary devices are most effective when you have at least 1 device per 5 acres and when they are elevated above the tree canopy.
The effectiveness of noisemakers can be increased somewhat when used in combination with visual repellents such as mylar streamers and "scare-eye" balloons. For example, scare-eye balloons may be attached to trees that are next to electronic distress call devices. This combination may increase effectiveness over using either approach by itself. Regardless of the approach used, much attention must be paid to bird responses when using frightening devices. When birds no longer respond negatively to a specific approach, you must switch to a different frightening tactic to continue to scare birds out of the orchard. At best, an appropriate rotation of frightening devices will control bird pests for a few weeks. Therefore, only use these scare tactics when needed to prevent birds from habituating to these auditory and visual repellents.
Birds that usually invade orchards in small numbers, such as scrub jays and magpies, can often be controlled by shooting. Check with California Department of Fish and Game officials before shooting any birds. A depredation permit is required if you want to shoot scrub jays. Permits are not presently required for shooting crows, magpies, or starlings that are causing damage, but it is a good idea to check with authorities because regulations may change. Where permissible, occasionally shooting at a few birds will increase effectiveness of your noisemaking techniques, because birds will begin associating loud noises with the real hazards of firearms.
Trapping can be an effective way to control house finches and starlings, especially if conducted over a relatively large area such as several orchards. The most effective trap for these species is the modified Australian crow trap. Successful trapping must take into account the behavior patterns of the birds being controlled. Place traps in suitable locations with adequate food, water, shade, and roost locations to keep the trapped birds alive. Trapping is best carried out by someone experienced with the technique. For house finches and crowned sparrows, trapping must be conducted under supervision of the County Agricultural Commissioner. Trapped birds are usually euthanized through the use of a CO2 chamber.
UC IPM Pest Management Guidelines:
UC ANR Publication 3440
R. A. Baldwin, UC IPM Program/Kearney Agricultural Center, Parlier