Managing Lophodermium needlecast
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
It’s time to think about management of Lophodermia needlecast disease of Scotch and red pine, caused by the fungal pathogen, Lophodermium seditiosum. The management of this needlecast disease is slightly different than other needlecast diseases found on Douglas fir and spruce. This disease can kill red pine seedlings and causes browning and massive amounts of needle loss on Scotch pines. Scotch pines infected with this disease have needles with brown spots surrounded by yellow margins, yellow needles or brown needles, especially at the bottom of the tree.
If you see Lophodermia needlecast on your trees right now, you must remember that what you are seeing is from infection events that took place last summer or fall. Therefore, now is the time to begin managing this disease for next summer. You cannot do anything about the amount of disease you see this year. In fact, the dead needles that are currently falling off the trees this summer (June, July and August) will be providing the inoculum (spores) that will spread throughout the trees in your plantation or nursery. These spores will infect this year’s crop of needles from August to October. Even though you won’t see the result of those infection events until next year, the fungus will stay in those healthy looking needles all winter until spring, when, again, those needles will begin the process of yellowing, browning and dropping off. To break this disease cycle, the time to manage this disease is in late July and throughout August, even into fall, if it stays warm and moist.
To initiate control, you must begin now. Look for needle spots and brown foliage on the lower branches of 50 or more trees scattered throughout the plantation. If ten percent of the trees are infected, consider treating the entire plantation by the first week of August. To reduce Lophodermium needlecast, plant long needle Scotch pines that are more resistant such as those from Germany, Belgian, Poland and Czechoslovakia; remove the branches of pine from cut stumps where spores are likely to be produced; and, make sure all the older pines have been removed from windbreaks near nurseries or plantations. These pines can serve as sources of fungal spores. Apply a registered, preventative fungicide three or four times, once every two to three weeks from late July through October.