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Sphaeropsis or Diplodia Blight Clean-up

October 17, 2006
Now is the time to try to clean up pines infected with Sphaeropsis blight (Diplodia blight). This disease was discussed in issue no. 7 of this newsletter. By now, infected trees are showing death of stem tips and needles. There may be areas of sappy cankers, as shown in the image.

These areas are easy to see in the fall. Prune out as many as possible while still maintaining a pleasing tree form.

The causal fungus is known to invade cones, where it can overwinter in fruiting bodies. The black, pinhead-sized structures on this image of pinecone are the fruiting bodies of the Sphaeropsis fungus.

There are hundreds of these fruiting bodies on this one pinecone alone.To help reduce spring inoculum that will infect new growth in 2007, rake and remove fallen cones. You can even remove cones on the tree if that is feasible.

Research has shown that drought-stressed pines are more susceptible to infection by this fungus. Therefore, give your pines some TLC and keep them watered in periods of drought lasting 2 weeks, especially in the heat of summer. Mulching with shredded bark or similar natural mulch is also recommended to help maintain soil moisture around these trees. That makes cone removal more difficult, but it is still possible, as I can attest. I think the advantage of using mulch is worth the extra effort to remove fallen cones in the mulch.

Fungicides may be used to help manage this disease, but fall applications are not recommended. So, for now, follow the above advice to help your pines look better in 2007. For more information on this disease, visit the Extension Vista Web site at http://www.ag.uiuc.edu/%7Evista/horticul.htm, and scroll down to “Sphaeropsis Blight or Diplodia Tipblight of Pines,” Report on Plant Disease (RPD), no. 625.