There are three important needle cast diseases of Scots pines grown in Kentucky landscapes and also in Christmas tree plantings. In general, the needle cast diseases caused by parasitic fungi begin with infections during moist periods; needles then develop dead spots or bands a few weeks or months later. Within a few more months, needles turn brown and drop from the tree, leaving only the newest growth unaffected. Often tiny, black, spore-bearing fungal fruiting structures can be seen embedded in the diseased needles.
Infections of needle cast caused by Cyclaneusma minus occur in spring and early summer and needles turn brown and fall over the next winter and spring. Other fungi cause brown spot needle blight (Mycosphaerella dearnessii) and another needle cast (Lophodermium seditiosum). Diagnosing these needle diseases often requires the aid of a professional diagnostician. Other diseases such as pine tip blight and pine wilt caused by the pine wood nematode also cause Scots pine needles to turn brown, but needles are not dropped as in needle cast diseases.
Managing pine needle cast diseases in the landscape: a) If necessary, cut and remove severely infected trees, particularly old, diseased Scots pines growing in windbreaks and fencerows. b) Prune healthy trees first to reduce movement of fungal spores. c) Do not prune infected trees during wet weather. e) Remove weeds from the planting to promote better air movement. f) If fungicides are needed, apply them at the proper time to get best results.
Contact your local Extension office for fungicide recommendations.
