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Grape Index
Chapter 17. Other Vineyard Pests
In addition to fungi, bacteria, viruses, and insects there are other larger vineyard pests. Some of these including birds, pocket gophers, rabbits, and deer can inflict severe damage on vines and/or fruit. Detailed information including sources of supply of equipment can be found in the California Vertebrate Pest Control Handbook (Clark, 1975).

Birds

Birds may eat the ripe fruit before it is picked; early-ripening fruit and isolated vineyards are especially vulnerable. The commonest devices used for controlling birds such as starlings, linnets, jays, crows, magpies, robins, and so on, are automatic acetylene exploders. These devices explode with a sound usually three times greater than that of a 12 gauge shotgun blast. One gun will usually protect about 40 acres (16.19 hectares). The units should be operating before bird damage begins, and should be moved around every 3 to 4 days as the birds become more quickly habituated to sound constantly coming from the same point. Intervals between explosions should also be varied. These guns are only partially effective, and the degree of effectiveness varies with the bird variety.

Biosonics, the study of animal communicator systems, is a new and promising area for investigation. Birds have various communication signals that include assembly, distress, and alarm calls. Phonograph records of distress calls are amplified and replayed into the vineyard to frighten the birds away. Currently, however, biosonics is not commercially feasible for large commercial vineyards, although it can sometimes reduce crop losses when used in conjunction with other methods.

Cage traps can be used for starling, blackbirds, grackles, and cowbirds (Zajanc and Cummings, 1965). Birds enter slots in the center section of a V-shaped cage top, but try to escape through the outer wall of the cage instead of the top. The best baits are foods the birds feed on in the vicinity. Trapping is often used around feedlots, although it is usually ineffective in vineyards since not enough birds are caught to reduce damage significantly.

Use of mesh nets over the vines is the only sure way to keep birds from getting to the fruit, but involves a high initial expense and maintenance problems. With small plantings, ripening grape clusters can be enclosed in paper bags.

Toxic bait should be used only when damage is extensive enough to warrant more drastic steps than the use of other methods, or when noisemakers, scare devices, repellents, traps, or exclusion do not provide adequate control. Prebaiting with nontoxic bait should be done before toxic bait is used. If birds readily consume the nontoxic bait, such as various types of seeds, most of the toxic bait will be eaten over a 24 hr period (Clark, 1975). Toxic bait should not be applied to the vines. A good method is to construct troughs in the vineyards to hold the bait (Fig. 17-1). Strychnine, often used as a toxicant, may be applied only under supervision of the state agricultural commissioner.

Deer

The best way to control deer is to fence them outside the vineyard area; a woven-wire fence will usually do the job (Longhurst et al., 1962). An electric fence may be useful in the summertime.

Taste repellents can also be used, but they are generally impractical because the repellent must be renewed each time it is washed off by rain. Improved Z.I.P. (a commercial ZAC Rhodoplex product with methocel added), Arasan 75, or Arasan 42-5 may be used in winter by brush or spray application (Anonymous, 1968). In the growing season, spray applications of Z.I.P. Arasan 75, or Arasan 42-5 can be employed. It may be necessary to apply repellents frequently to cover new growth.

Pocket Gophers

These rodents can girdle vines near the soil level. They dig furrows in the soil about 2-3 in. (5.08-7.62 cm) in diameter and 4-12 in. (10.2-30.5 cm) below the surface. These furrows can cause substantial irrigation water loss and create other watering problems (Cumming, 1971). They must be killed by trapping, or the use of bait prepared with strychnine alkaloid, or other bait (Marsh and Cummings, 1974). A mechanical bait applicator has been developed.

Fig. 17-1. Baiting trough in vineyard, used for holding bait for bird control. (After Clark, 1975).

Rabbits

Rabbits can kill vines in young vineyards by chewing the bark and leaves. The best protection is to fence off the area with a mesh fence 2½ ft (76.2 cm) high with about 6 in. (15.2 cm) of wire buried in the ground to prevent burrowing (Jacob, 1950).
Continue to Chapter 18