Abstract

ABSTRACT

SANTAMOUR, F.S., JR. 1982. Which white birches are least susceptible to bronze birch borer? Am. Nurseryman 156(11): 61-63.

Bronze birch borer has damaged many birches in recent years, but detailed, long-term research on susceptibility has been lacking. Several years ago, Dr. Knud E. Clausen and I reported on the four-year growth and survival of various seed sources of several of these species. Bronze birch borer (Agrilus anxius) began attacking these trees during their fifth growing season, and the insect population has remained extremely high since that time. In September, 1982, when trees were 10 years old, we surveyed the entire planting to obtain data on potential borer resistance. Survival after exposure to borer attack for each species is based on the number of trees that were alive in 1976. These tests have probably been the most extensive trials of white-barked birches for borer resistance ever conducted in the U.S. Our results clearly demonstrate that none of the major species can be relied on to provide the degree of borer resistance necessary for long-term utility in landscapes.