What are the horizontal holes on my trees?

Sap suckers, a close relative of woodpeckers, cause damage to trees that is often attributed to wood boring insects. They visit a tree many times, feeding on sap accumulated in the holes they have drilled. Sap sucker damage appears as rows of holes circling or running vertically on the trunk or larger limbs of the tree.

This contrasts with emergence holes of borers that occur in a random pattern on the trunk or in limbs of a tree. Contrary to popular belief, these birds rarely, if ever, dig through bark to capture wood-boring insects, but rather feed on cambium and sap in the phloem. The tree species most attacked by sap suckers are pine, sugar maple, birch, willow, magnolia, apple, and pecan.

In Oklahoma, the yellow-bellied sap sucker is the most common species that damages trees. They winter in the South and spend the summer in the northern part of the United States. Thus, they often cause damage during their migrations in the spring through early summer, and again in fall in Oklahoma.

Control – Woodpeckers are classified as migratory, non-game birds and are protected by the Federal Migratory Bird Treaty Act, so killing them is out of the question. To protect trees from sapsuckers, wrap barriers of 1/4-inch (0.6-cm) hardware cloth, plastic mesh, or burlap around injured areas to discourage further damage. This method may be practical for protecting highvalue ornamental or shade trees. In orchards and forested areas, it may be best to let the sapsuckers work on one or more of their favorite trees. Discouraging them from select trees may encourage the birds to disperse to others, causing damage to a greater number of trees.

Frightening Devices – Visual. Stationary model hawks or owls, fake and simulated snakes, and owl and cat silhouettes are generally considered ineffective as repellents. Toy plastic twirlers or windmills fastened to the eaves, and aluminum foil or brightly colored plastic strips, bright tin lids, and pie pans hung from above, all of which repel by movement and/or reflection, have been used with some success, as have suspended falcon silhouettes, especially if put in place soon after the damage starts. The twirlers and plastic strips rely on a breeze for motion. Large rubber balloons with owl-like eyes painted on them are included in the recent array of frightening devices used to scare woodpeckers.

A good deal of attention has recently been given to round magnifying-type shaving mirrors installed over or adjacent to damaged areas to frighten woodpeckers with their larger-than life reflections. Success is sometimes reported by those using the method and this encourages further testing.

Sound. Loud noises such as hand clapping, a toy cap pistol and banging on a garbage can lid have been used to frighten woodpeckers away from houses. Such harassment, if repeated when the bird returns, may cause it to leave for good. Propane exploders (gas cannons) or other commercial noise-producing, frightening devices may have some merit for scaring woodpeckers from commercial orchards, at least for short periods. Because of the noise they produce, they are rarely acceptable near inhabited dwellings or residential areas.

Around homes, portable radios have been played with little success in discouraging woodpeckers. Expensive high-frequency sound-producing devices are marketed for controlling various pest birds but rarely provide advertised results. High-frequency sound is above the normal audible hearing range of humans but, unfortunately, above the range of most birds too. Woodpeckers can be very persistent and are not easily driven from their territories or selected pecking sites. For this reason, visual or sound types of frightening devices for protecting buildings — if they are to be effective at all — should be employed as soon as the problem is identified and before territories are well established. Visual and sound devices often fail to give desired results and netting may have to be installed.

Repellents – Taste. Many chemicals that have objectionable tastes as well as odors have been tested for treating utility poles and fence posts to discourage woodpeckers. Most have proven ineffective or at least not cost-effective.

Odor – Odors such as from naphthalene (mothballs) and wood treatments, such as creosote and pentachlorophenol, are of doubtful merit and do not resolve the woodpecker problem.

Tactile. Sticky or tacky bird repellents such as Tanglefoot, 4-The-Birds, and Roost-No-More, smeared or placed in wavy bands with a caulking gun on limbs or trunks where sapsuckers are working, will often discourage the birds from orchard, ornamental and shade trees.

These same repellents can be effective in discouraging birds if applied to wood siding and other areas of structural damage. A word of caution: some of the sticky bird repellents will discolor painted, stained or natural wood siding. Others may run in warm weather, leaving unsightly streaks. It is best to try out the material on a small out-of-sight area first before applying it extensively. The tacky repellents can be applied to a thin piece of pressed board, ridged clear plastic sheets, or other suitable material, which is then fastened to the area where damage is occurring.

Trapping – Live traps have been tried in attempts to capture woodpeckers for possible relocation rather than killing the birds. None of those explored were very successful, and more research is needed to develop an effective woodpecker live trap.