The Austrian pine has long been a staple in American landscapes, having arrived from central Europe shortly after the Revolutionary War. With its moderate growth rate, extraordinary adaptability and attractive appearance, the Austrian pine has become a favorite of landscape architects and homeowners. Highway engineers and urban planners appreciate the tree's tolerance for road salt, drought and air pollution. Another key asset has been its freedom from major disease or insect problems. Unfortunately, that is no longer true in the Midwest, where Austrian pines are being seriously threatened by tip blight and a tiny parasite. Diplodia, the fungus that causes tip blight, has made its presence obvious from Pennsylvania west to Michigan and Missouri in the last decade. It disfigures Austrian pines (Pinus nigra) and, to a lesser extent, Scotch pines (P. sylvestris) and mugo pines (P. mugo mugo). Perhaps because these trees are not native to the United States, no natural enemy is combatting the diplodia. The diplodia tip blight fungus was isolated in Europe in 1842, and was first noticed in this country on non-native pines in New Jersey in 1917. It is not usually fatal, but can seriously disfigure a tree while contributing to its decline. Austrian pine needles normally live for three to five years before dropping; trees produce new needles in the "candles" that form in spring at active growing tips. Diplodia attacks the unfolding candles of mature Austrian pines, causing an infection if needle surfaces remain wet. Needles infected by diplodia die and turn brown by midsummer, but cling to the branches, stuck there by the trees' own sap. Two or three consecutive wet springs that result in diplodia can seriously limit a tree's ability to sustain itself.
