Now is the time to be taking measures to control Diplodia tip blight.
Diplodia tip blight is a common serious disease on Austrian, ponderosa, and mugo pine in Iowa, and also occurs less destructively on Scots pine. It is caused by the fungus Sphaeropsis sapinea. Symptoms range from tip blight, cankers on branches or trunk, death of cones, and blight of seedlings. Tip blight occurs when the fungus infects buds or shoots. Stunted, brown shoot tips with short needles result. Tissues are often resin-soaked. In the fall, small black fruiting structures of the fungus can be seen on needle bases. The annual death of buds and shoots causes trees to decline gradually from the bottom branches upward. The fungus may also penetrate young stems and cause cankers which eventually girdle and kill branches. Fungal spores are spread during wet weather from early spring until fall. Infected cones serve as a source of spores.
- Avoid planting Austrian pine.
- Promote good air circulation by adequate spacing and weed control.
- Trees may be pruned to improve their appearance, but this does not control the disease.
- Spray chlorothalonil, benomyl, thiophanate-methyl, Bordeaux mixture, or other appropriately labeled copper fungicides at bud swell, then repeat twice at intervals of 10-14 days.
This article originally appeared in the April 29, 1992 issue, pp. , 1992 issue, pp. 67-68.
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