Photo courtesy of the University of Minnesota Bell Museum of Natural History How to...
Identify and control sapsucker injury on trees

North Central Forest Experiment Station
Forest Service
U.S. Department of Agriculture
St. Paul, Minnesota



  Image courtesy of the National Museum of Canada
   

The yellow-bellied sapsucker (Sphyrapicus varius), a member of the woodpecker family, is a migratory bird whose summer breeding range includes the Lakes States region. The identifying field markings of adult birds are a black crescent on the breast, pale yellow belly, white wing stripe, and a crimson crown. The male also has a crimson chin and throat, distinguishing him from the female whose chin and throat are white.

Although insects make up part of its diet, the sapsucker is better known for its boring of numerous holes in the bark of live trees to obtain sap, the activity from which it derives its name. The yellow-bellied sapsucker is the only member of the woodpecker family to cause this type of injury. More than 250 species of woody plants are known to be attacked. Birch, maple, and hemlock are the preferred species in the Lakes States.


The sapsucker bores neat rows of 1/4-inch holes spaced closely together through the bark of trees along and around portions of the limbs or trunk. As these holes fill with sap the sapsucker uses its brush-like tongue to draw it out. These holes are periodically enlarged and portions of the cambium and inner bark, together with the fresh sap, are eaten.

Puncture wounds and resulting sap flow on branches and trunks of trees are the most obvious symptoms of injury inflicted by the sapsucker.

After repeated attacks on the same area of a tree, large patches of bark may be removed. If this area is girdled, the portion of tree above this point will die. Many small limbs are killed and some- times the trunk is girdled and the whole tree is killed. Sapsucker feeding on shade and ornamental trees leaves unsightly bleeding wounds that attract bees, hornets, and other insects to the sweet, oozing sap. On forest trees these wounds may attract porcupines or red squirrels that further injure the trees through feeding.

Early in the spring the sapsucker tests many trees around its selected nesting site by making sample drillings before selecting ones it prefers. These trees, because of quantity or sugar content of the sap, are visited several times a day for the rest of the season and sometimes are used as a food source for several years.

Feeding wounds serve as entry courts for a wide variety of wood decay or stain fungi and bacteria. On high quality hardwoods, sapsucker wounds cause a grade defect called "bird peck" that lowers the value of the trees. Many forest trees are attacked high in the crowns, making light feeding wounds or sample drillings less evident. A condition known as black bark may develop which results from certain fungi colonizing the sap flow and discoloring the bark, and is good evidence that injury exists. Black bands can develop on white birch as a result of a healing reaction to sapsucker injury.

Control

To discourage sapsuckers from feeding on a favorite shade tree, wrap hardware cloth or burlap around the area being tapped or smear a sticky repellent material, such as bird tanglefoot, on the bark.

In commercial forests or orchards, leave favorite feeding trees of the sapsucker untreated. Birds will concentrate their feeding activities on these favorite trees, which often protects nearby trees from serious injury.

Sapsuckers in search of nesting sites are especially attracted to aspen (Populus tremuloides) infected with Fomes igniarius var. populinus, which decays the heartwood and enables the birds to excavate a nest hole. To protect a valuable timber stand eliminate such infected trees within the stand during a precommercial thinning; this may discourage sapsuckers from using the area.

The Migratory Bird Treaty Act and Federal regulations promulgated under its authority prohibit shooting of sapsuckers. Shooting of this species would be an ineffective control anyway because transient birds tend to replace occasional losses to local sapsucker populations.



MICHAEL E. OSTRY
   Forestry Technician
THOMAS H. NICHOLLS
   Principal Plant Pathologist
   North Central Forest Experiment Station
   St. Paul, Minnesota
 
Produced in Cooperation With:
   Wesley R. Jones
   U.S. Fish & Wildlife Service
   Federal Building, Fort Snelling
   Twin Cities, Minnesota 55111

Forestry Research   Bicentennial
 
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