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Since I have had a rash of reports about strange rows and columns of holes in trees, I thought it would be a good time to update the subject for everyone. There are those who say that holes drilled in limbs and trunks is just cosmetic and doesn't hurt the tree. That's incorrect on two accounts. The drilling indeed does hurt and can kill trees. Secondly, the work of these woodpeckers indicates serious stress in the trees.

    

The following are quotes from the book in the chapter on Yellow Bellied Sapsuckers - under "Relation to Wounded Trees".

Sapsuckers feed on a wide variety of trees. Regardless of the tree utilized, it is not always clear why they concentrate on a few, leaving others untouched. In the summers of 1962 and 1963, I found three places in Lyme that seemed to provide answers. One centered on a row of paper birches bordering a dirt road and badly bruised by snow plows.

Practically all of the birches with sapsucker holes were ones with scars. Other birches of similar size and adjacent to them, but unwounded, had none. Two feeding trees stood back from the road. Although untouched by the plow, they had extensive injuries of unknown origin below their bands of drill holes.

I found sapsuckers making small bands [of holes] on healthy birches nearby. These bands were at the same height as the main feeding holes, but drilling was casual, as if not more than a displacement activity.

I watched sapsuckers where hundreds of unwanted or weed trees had been girdled by foresters. Most of the trees in one area, not much affected by being girdled the previous winter, still had canopies. Trees in another region, in contrast, in a second summer after girdling, were either dead or dying by August. The dying trees were the ones that attracted the sapsuckers, which drilled just above the girdles.

The three patterns, encountered on a single species, show that the drilling of sapsuckers is related to the underlying physiology of the tree.

Sapsuckers obtain theirs [sap] by repeated wounding. This leads to an increased flow of nutrients, an effort of the tree to repair the injury that nutrients will accumulate above a girdle, as indicated by a layer of thickened wood. 

Sapsucker Damage

The injury from these birds is a solvable problem. First, splash hydrogen peroxide on the wounds, then smear on Tree Trunk Goop which is one third each of compost, soft rock phosphate and natural diatomaceous earth. Then apply the Sick Tree Treatment to improve the health of the tree.  As Kilham’s research would suggest, the birds will no longer be attracted to the trees.

To help keep these beautiful pests from damaging your trees in the first place, use gentle organic fertilizers only; use none of the high nitrogen synthetic stuff; make sure the soil is aerated rather than compacted; avoid physical damage to trunks and limbs; maintain the proper soil moisture, and remove the soil from the root flares. Arborists can do this work with the Air Spade or Air Knife.

The damage shown below is a different pest. The bleeding and random holes indicates borer beetle larvae.
  

Here are some web sites with additional information on sapsuckers:

http://birds.cornell.edu/wp_about/biology.html

http://www.na.fs.fed.us/spfo/pubs/misc/sapsucker/ne-136_concern.htm

                                                  

    Sapsucker damage on ginkgo trunk.
                                    

QUESTION: I have two ornamental pear trees that are more than 17 years old. I recently noticed four rows of almost perfect holes, one row on top of the other, on one of the tree trunks. I have heard woodpecker sounds, but I also worry that I may have insect pests. G.M., Sherman

ANSWER: Sapsuckers are woodpeckers that drill holes in rows and columns. They are seeking concentrated sugars that accumulate in stressed trees. Even if your trees look healthy, the bird damage indicates that the trees need help. Use my Sick Tree Treatment.