Sphaeropsis Tip Blight
One of the most serious pine diseases in our area is Sphaeropsis tip blight. Pine trees may be seriously injured or killed by this fungal disease. Austrian, ponderosa, Scots and mugo pines are all susceptible to the disease. Tip blight is most severe on mature Austrian pines, but the disease can occur on susceptible pines of any age. Tip blight causes the death of new shoot growth in the spring, and repeated infections can result in the death of large branches or even the entire tree.
These are the symptoms of Sphaeropsis tip blight: in late May or early June, you will notice that the new, developing shoots (or candles) fail to elongate properly. Then they turn yellow or tan. Small droplets of resin often form on the stunted needles, and the infected needles remain attached to the branch. Dead shoots are more common in the lower portion of the tree crown. Sphaeropsis tip blight can be confused with winter damage or injury sustained from the pine tip moth. So remember that tip blight results in stunted, yellow to tan shoots in late spring after needle elongation has begun. In contrast, winter damage normally results in death of shoots before needles emerge in the spring and the injury may be restricted to one side of the tree. For a precise diagnosis take a fresh branch sample showing the disease in progress to the County Extension Office.
The tip blight fungus survives from year to year in dead shoots, branches and pinecones. The fungus is dispersed by water and needs high humidity to germinate and penetrate the host tissue. New shoot growth is very susceptible to infection and, therefore, most infection occurs in the spring when the candles are elongating.
The control of Sphaeropsis tip blight is aimed at protecting the vulnerable, growing shoots from fungal infection in the early spring. Tip blight can be controlled with two to three applications of the correct fungicide, if the fungicide is applied at the right time. The first application should be made about the third week of April, with a second application 10-14 days later, and a third about mid-May. Spraying after the critical period of bud break and elongation will not be effective in controlling tip blight. Call your County Extension Office for current information on those fungicides that are most effective against tip blight.
Tip blight is more severe on stressed trees. Pines should be spaced so there is ample air circulation, be grown in non-compacted, well-drained soil, and be adequately watered during periods of drought.