Diplodia tip blight is a serious disease of mature Austrian, Scots (Scotch), and Mugo pines in Kentucky. The disease is caused by the fungus Sphaeropsis sapinea. In the landscape, tip blight is normally not observed until pines reach about 12 years old and begin to bear cones. Continuous infections (3 to 5 consecutive years) can greatly weaken and eventually kill affected pines.
Infection occurs in spring; however, disease symptoms become more obvious in mid- to late-summer and fall. Needles in early stages of development stop growing as a result of shoot infections. These stunted needles eventually die and turn straw-colored (Figure 1). Infection progresses to healthy needles and cones.
· Apply fungicides (chlorothalonil, propiconazole, or thiophanate methyl) to trees just as buds swell in spring. Apply a second spray when the candles are about half elongated and a third spray as needles begin to emerge from the needle sheaths.
· Remove and destroy dead twigs, branches, and cones as they occur. Do not prune when trees are wet.
· Destroy all blighted needles, twigs, and cones debris as they fall to the ground. The fungus overwinters in debris, especially infected cones and diseased needles.
· Trees under stress tend to be more susceptible to tip blight. Fertilize and water trees as needed to promote vigor.
For more information on tip blight or pine diseases:
Needle Cast Diseases of Conifers http://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdf
Twig, Branch, and Stem Diseases of Pine http://www2.ca.uky.edu/agc/pubs/ppa/ppa16/ppa16.pdf
Department of Plant Pathology, Extension Publication page http://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.html