The yellow-bellied sapsucker (Sphyrapicus varius) is the primary cause of sapsucker damage on trees in the eastern United States (Ostry and Nicholls 1976). This migratory bird winters in the south and summers in northern states. In the Carolinas, U.S., the birds cause damage from November through March. Insects are a major part of this species diet; however, it is best known for making small wounds in stems and large branches and feeding on either phloem or xylem sap that oozes from the wounds. Phloem sap is the main source during the summer breeding season (Tate 1973; Eberhardt 2000), whereas xylem sap is more readily available from deciduous trees after leafdrop in the winter. Sapsuckers will test many trees and select only those that have the highest quality sap to feed on repeatedly. Sugar and amino acid levels are often highest on trees that have injuries that restrict sap movement (Kilham 1964; White 1984). Similarly, sapsuckers are thought to choose trees in poor health (Eberhardt 2000).
Symptoms of repeated feeding are horizontal rows of 1 cm (0.04 in) diameter holes in the bark. These wounds ooze sap that the bird feeds on. Excess sap may run down the surface of the bark and promote the growth of dark-colored fungi, a condition called “Black bark” (Minnesota Department of Natural Resources 1999). Insects and animals, including squirrels, porcupines, hummingbirds, ants, hornets, and wasps, are also attracted to this sap food source (Minnesota Department of Natural Resources 1997). Some of these may cause more damage to the tree.
Although most trees do not exhibit severe decline from sapsucker attack, some studies have found a loss of growth and crown dieback associated with severe girdling (Erdmann and Oberg 1974; Eberhardt, 2000). Sapsuckers have also been found to cause damage, which results in ring shake and the entrance of wood decay (Shigo 1963).
Wrapping trunks and branches with burlap is the traditional method to deter sapsucker wounds (Minnesota Department of Natural Resources 1999). However, no published studies could be found that quantify the effectiveness of this treatment. This study was undertaken to determine the effectiveness of two different trunk wrap materials, burlap and polypropylene tree wrap, for preventing sapsucker feeding.
MATERIALS AND METHODS
Fifteen sugar maples (Acer saccharum) with evidence of active sapsucker damage were selected at the Bartlett Tree Research Laboratories in Charlotte, NC, U.S. Mean trunk diameter measured at 1.4 m (4.6 ft) was 23.7 cm (9.5 in) with a standard deviation of 13.1 (5.1). Black electrical tape was used to divide affected tree trunks into three 60 cm (24 in) sections.
One of three treatments was randomly applied to each section on each tree on 9 February 2006. The treatments were:
Nontreated control;
Natural burlap fabric; and
Polypropylene tree trunk wrap 76 mm (3 in) wide (DeWitt, Sikeston, MO).
Burlap was cut into the largest piece that would cover an area of the trunk and stapled into place with T-32, 7.8 mm (0.31 in) staples (Arrow Fastener Co., Saddle Brook, NJ). Edges of the burlap were overlapped approximately 2 cm (0.8 in) when multiple sections were used. The trunk wrap was spiraled around the trunk with approximately 25% overlap and stapled at both ends. Additional wrapping and stapling was used as needed to keep wraps close to the trunk and to reduce gaps around branches.
On each stem section, the numbers of “active” and “bleeding” wounds were counted on a weekly basis. Active wounds had exposed live phloem with no evidence of callus growth. Bleeding wounds had the characteristics of active wounds plus they had sap flowing from them (Figure 1). Trees were evaluated before treatment on 9 February 2006 after treatments were applied on 16 and 24 February and 3 and 10 March 2006 by counting the active and bleeding wounds on each treated and untreated section of stem. After treatments were removed on 11 March 2006, all previously covered areas were inspected for the presence of previously undetected sapsucker damage.
A bleeding wound in the bark of sugar maple (Acer saccharum) created by sapsucker (Sphyrapicus varius).
Data were analyzed using an analysis of variance with separation of means using the Student Newman-Keuls procedures (SPSS, Chicago, IL; P = 0.05).
RESULTS
Burlap was much faster to install and easier to work with than the tree trunk wrap. This was because of the larger pieces of burlap that could be used as well as the pliability of the burlap. With the tree wrap, there were many large gaps between the bark and the trunk that need to double-wrapped or fastened down with additional staples to reduce the gaps.
There were highly significant differences in the number of active and bleeding wounds between treatments and the controls. Both the tree wrap and burlap treatments completely prevented feeding by sapsuckers in the protected areas of the trees (Figures 2, 3, and 4). There were no significant differences in the number of bleeding wounds before treatment or at the 10 March count. No wounds were found under the burlap or trunk wrap after it was removed at the end of the trial.
The number of active wounds created by Sphyrapicus varius before and after trunk wrapping treatments on 60 cm (24 in) sections of Acer saccharum stems. The mean number of wounds was significantly different after 16 February 2006.
The number of bleeding wounds created by Sphyrapicus varius before and after trunk wrapping treatments on 60 cm (24 in) sections of Acer saccharum stems.
Sapsucker (Sphyrapicus varius) feeding on control treatment between tree wrap (top) and burlap (bottom) of Acer saccharum stem.
DISCUSSION
The traditional trunk wrapping treatment for sapsuckers works extremely well to both stop ongoing attacks and prevent new damage. Increasing attacks on the control areas may indicate that the bird has changed its feeding habits, going from the treated area to the control area. This may have implications for susceptible trees near treated trees.
There are anecdotal reports that sapsuckers in the western United States are not deterred from damaging trees wrapped with burlap. A study of western sapsuckers is required to clarify the effectiveness of wrap treatments in that area.
It was thought that using a trunk wrap instead of burlap might speed the installation process and be more effective than burlap, but that did not turn out to be the case. Burlap was easier to install and remove, and both products were equally effective at preventing sapsucker damage.
Although trunk wrapping did protect treated trees, it is a very time-consuming operation and the treatment could be considered unsightly by many consumers. Further study is needed to find effective treatments that can be applied more rapidly.
Acknowledgments.
We express our appreciation to Robert A. Bartlett Jr. and the Bartlett Tree Expert Co. for their support of this research and to Bruce R. Fraedrich, Director of the Bartlett Tree Research Laboratories.
- © 2007, International Society of Arboriculture. All rights reserved.
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