Many Austrian pines have been arriving in the Plant Disease Clinic showing symptoms of the disease Dothistroma needle blight. This fungal disease causes yellow to reddish-brown spots or bands on needles. Needles die from these banded areas to the tip. Diseased needles will eventually fall from the tree. Infection by the fungus usually occurs first on lower branches and spreads upward. For photos of disease symptoms, refer to Pm-1528 "Common Diseases of Conifers in Iowa".
To control Dothistroma needle blight:
- Apply Bordeaux mixture or other copper-containing fungicides in mid-May and again 4 to 6 weeks later.
- Improve tree vigor through mulching and watering, as needed.
- Do not shear trees when foliage is wet.
- Promote good air circulation by adequate spacing.
- Avoid planting Austrian pine.
This article originally appeared in the April 28, 1995 issue, p. 49.