Dothistroma needle blight of Austrian pine
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.
Dothistroma needle blight is caused by the fungus Mycosphaerella pini. This common pine pathogen kills needles of all ages and can weaken or kill Austrian pine trees. The main symptom is dead needle tips beyond the yellow to tan needle spots that enlarge to form distinct brown to reddish-brown bands. The black fruiting bodies of the fungus can be seen in the dead spots or bands on the needles. The spores spread by wind and rain and can infect needles throughout the growing season. New needles are susceptible once they emerge from the needle sheaths. The black fruit bodies appear in the fall; however, the spores are released the following spring and summer.
The best protection of new needles can occur when applying copper-based materials as the new needles emerge from the needle sheaths and as the spores are released from the fruiting bodies. This is usually June and July. To protect foliage from infection, apply a registered fungicide such as Basicop in mid-June through mid-July. This year you might start earlier since trees are ahead of normal. Repeat the application two or three times as needed at 7 to 10 day intervals. Before spraying in June, the best management plan would include checking all trees in the plantation and nearby windrows in the fall, and if you find any Dothistroma needle blight then, consider spraying in June the following year. Help yourself by not planting Austrian pines near windbreaks composed of Austrian pine. Reports suggest that removal by pruning of infected branches helps reduce disease.
Dr. Fulbright's work is funded in part by MSU's AgBioResearch.