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Sphaeropsis of Pine: Should You Spray?

May 15, 2002

Sphaeropsis blight of pine is a fungal disease that commonly infects Scotch, Austrian, and mugho pines in Illinois. Until a few years ago, we traditionally saw infected stem tips die with brown, withered needles remaining attached throughout the season. The disease was, until recently, a tip blight. Unfortunately, a new pathotype of this fungus "invaded" a few years ago. It causes a damaging, sap-oozing canker on limbs of affected trees. Often, the branch dies beyond the canker, resulting in a very unpleasant-looking tree.

Managing this disease is difficult. Some of the most intense infection takes place in the spring as new growth emerges. This growth is very susceptible, especially in wet weather, until about mid-June. It helps to remove dead wood and needles to reduce the amount of the fungus in the area. Do this when the tissue is dry so you don't increase disease spread. It helps to get rid of cones. On an infected tree, the cones are usually full of fruiting bodies of the fungus. Because drought-stressed trees are more susceptible to canker infection, we recommend watering infected trees in periods of extended drought.

Chemical options are available to control this disease. The recommendation is to use a systemic product and apply it three times, following label directions. Usually this is as buds begin to expand, at half candle, and at full candle. In central Illinois, we are currently at about half candle. This means the new growth (the candle) is elongating, but needles are not yet expanded. I have heard testimonials from a few local growers that chemical applications protected their trees in the year they sprayed and that infection was heavy in an unsprayed year. I have also heard from people who say sprays did not work. Recent research has shown that even symptomfree foliage is often infected. That research questions the use of chemicals intended to prevent infection. In summary, it is still very much recommended that you follow the cultural controls discussed. The use of chemicals may still be of benefit but should be used in addition to cultural controls. Choose a systemic product from those listed in the Illinois pest-management handbooks and follow label timing precisely.

For details about this disease, consult Report on Plant Disease (RPD) no. 625, "Sphaeropsis Blight or Diplodia Tip Blight of Pines," available in Extension offices or on the Illinois Extension Vista Web site.

Author: Nancy Pataky


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