Sphaeropsis blight of pine is the disease that some may remember as Diplodia tip blight. The disease has become severe on pines in Illinois. It is the most common disease cause of tip and branch death on pines in the state. This is a disease nurserymen and gardeners alike should recognize. New needles that are emerging now are very susceptible to infection.
Sphaeropsis blight is common on Scotch, Austrian, and mugho pines in Illinois. It is rare on white pine. Infected trees may show branch tip dieback, with needles remaining attached throughout the season. Limbs of affected trees may have damaging, sapoozing cankers. Often the branch dies beyond the canker, resulting in an unpleasant-looking tree. Severely infected trees may be confused with those killed by pine wilt.
Management of this disease is difficult. Some of the most intense infection takes place in the spring as new growth emerges (now). This tender growth is very susceptible to infection, especially in wet weather, until about mid-June. We know that it helps to remove dead wood and needles, to reduce the amount of the fungus in the area. This should be done when the tissue is dry so you don’t increase disease spread. We also know it helps to get rid of cones. On an infected tree, the cones are usually full of fruiting bodies of the fungus. The final point of which we are certain is that drought-stressed trees are more susceptible to canker infection. Therefore, we recommend watering infected trees in extended periods of drought. Drought was common this winter in Illinois. Many areas still have not received much rainfall. Supply an inch or more water per week to pines in the drought stressed areas. Prune out dead branch tips and cankered wood in the next dry period. Remove this material from the site.
There are chemical options available to control this disease. The recommendation is to try to use a systemic product and to apply it three times, following label directions. Usually this timing is as buds begin to expand, just before new needles emerge from the sheath, and 10 to 14 days later. Recent research on this disease has shown that even foliage with no symptoms is often already infected; that research questions the use of chemicals intended to prevent infection. It is still recommended that you follow the cultural controls discussed above. The use of chemicals may still be of benefit but should be used only in addition to cultural controls: Do not rely on chemical control alone. Choose a systemic product from those listed in the Illinois pest management handbooks and follow label directions precisely.
For details about this disease, consult Report on Plant Disease, no. 625, “Sphaeropsis Blight or Diplodia Tip Blight of Pines.” This publication is available in Extension offices or on the U of I Extension Vista Web site.