Cause Mycosphaerella pini (asexual: Dothistroma septospora). Formerly Scirrhia pini (asexual: Dothistroma pini). The red band disease has caused serious losses in some Christmas tree plantings of hard pine (two- and three-needle pines), Scots pine (Pinus sylvestris), Austrian pine (P. nigra), and shore or lodgepole pine (P. contorta). Five-needle pines also are reported to be susceptible. The fungus attacks both current-season needles and needles produced in past seasons. Black, asexual fungal structures (stroma) mature 1 to 2 years after initial infection. Spores produced within the stroma are spread long distances by rain and wind to cause new infections. Usually by mid-August all spores have been disseminated. Spores germinate under moist conditions and penetrate stomata. A toxin, dothistromin, diffuses into the tissue ahead of the fungus, killing plant cells.
Symptoms Chlorotic spots on infected needles in fall and winter. Spots gradually spread, turn red-brown, and girdle the needles, killing the distal end while the base stays green. In early spring, a black fungal growth (stromata) erupts through the needle epidermis. Affected trees may defoliate during the growing season, rendering the trees useless for sale. Reduced growth rate is another result of annual defoliation.
- Avoid using seed from susceptible (off-site) tree sources.
- Prune the lowest whorl of branches at first opportunity.
- For high-value trees, remove and destroy fallen needles that collect in branch crotches and on the ground.Avoid planting in low-lying areas with poor air drainage.
- Space plants for good air circulation.
- Forest trees-thinning stands is helpful.
- Control weeds and vegetation around the bases of trees.
- Shear trees during dry weather.
Chemical control Apply just before budbreak and again a few weeks later.
- Bordeaux 8-8-100. Can be toxic to new needles. O
- Bravo Weather Stik at 5.5 pints/A. 12-hr reentry.
- Echo 720 at 5.5 pints/A. 12-hr reentry.
- Ortho MAX Garden Disease Control at 5 teaspoons/4 gal water. H
- Penncozeb 75 DF at 2 to 4 lb/A. 24-hr reentry.
- Phyton 27 at 1.5 to 2 oz/10 gal water. 24-hr reentry.
References Peterson, G.W. 1965. Dothistroma needle blight of Austrian pine: infection and control. Plant Disease Reporter 49:124-126.
Dale, A. L., Lewis, K. J., and Murray, B. W. 2011. Sexual reproduction and gene flow in the pine pathogen Dothistroma septosporum in British Columbia. Phytopathology 101:68-76.