Sphaeropsis blight of pine has become one of the most common landscape diseases in Illinois. It causes death of branch tips, browning of needles at branch tips, and sappy cankers that girdle branches. With a little work on infected pines now, you can make a big difference in the appearance of those trees this summer, while reducing inoculum to other trees.
The causal fungus, Sphaeropsis pini, survives over the winter on infected needles, stems, and cones. If your tree is infected, take a close look at the cones. Each cone will be covered with hundreds of black fruiting bodies of this fungus. They appear as black, pinhead-sized structures embedded in the cone. It is easy to see that each cone could serve as a very effective source of inoculum for further infection. Infection occurs with warm, wet weather, when new needles begin to emerge. The succulent new growth is a primary infection site. For these reasons, removal of infected material is usually done in the dormant season. If you have not already done so, remove infected material now! If possible, wait until foliage is dry.
Infected tissues include cones, brown needles, and dead stems. Rake and remove cones from the site. Prune out dead branch tips that can be reached. Remove cankered wood where possible or where doing so does not disfigure the tree.
Research has shown that drought-stressed trees are more prone to infection than healthy trees. Be sure to water pines in periods of drought this growing season.
For details on this disease refer to a past HYG article, “Sphaeropsis Blight of Pine,” no. 1, 2001. Also consult Report on Plant Disease, no. 625, “Sphaeropsis Blight or Diplodia Tip Blight of Pines,” available under horticulture publications at http://www.ag.uiuc.edu/%7Evista/ or in your local Extension office.
There has been debate over the last few years as to the value of fungicide protection of pines against Sphaeropsis blight. Read details in HYG, no. 4, 2002, before you decide whether to invest this time and money. The first sprays should be applied at bud break, so do not delay this decision.