||Dying branch tips on Austrian pine (Pinus nigra) caused by sphaeropsis tip blight of pines
Sphaeropsis tip blight is caused by the fungus, Sphaeropsis sapinea (also known as Diplodia pinea). It is one of the most destructive fungal diseases of pine trees in the Midwest. It is most common on Austrian pine but can also damage Scotch pine (Scots pine), ponderosa, and mugo pine. If not controlled, over a period of years, it will weaken and perhaps kill the tree.
Symptoms and Diagnosis
Tip blight most commonly affects trees 13 or more years old that bear mature pine cones, but it can also affect younger trees. The most obvious symptom is the browning and stunting of the needles of the new growth. The needles are retained on the tree. Excess resin flow builds up on the dead twigs and needle bases. Small black pimples (pycnidia) about the size of fly specks are very noticeable on the bases of the browned needles, on the dead twigs, and on the cone scales. The pimples are the fruiting bodies of the fungus. Infection usually begins on the lower branches and moves up the tree. Sphaeropsis tip blight may be confused with pine tip moth damage. In the case of the latter, the fungal fruiting bodies will not be present, but moth larvae and tunneling in the shoots will be evident.
Symptoms of tip dieback are most common in spring from April to mid-June when the young emerging needles are soft and tender. They are most vulnerable for the two weeks when the buds first open. Spores are released from the fruiting bodies (pycnidia) and are moved by splashing rain, wind, animals, and pruning equipment. They are dispersed throughout the year. Under very moist, humid conditions, the spores germinate and infect the needles. Once the fungus infects the needles, tissue is destroyed and shoots and needles are stunted. Infected second-year cones are a major source of inoculum. Infected cones are often observed on plants that show no other signs of infection. Latent infection is common and may be symptomless.
Integrated Pest Management Strategies
1. Keep trees healthy. Weakened trees are more susceptible to disease. Water during dry periods and fertilize according to soil test recommendations. Spores of Sphaeropsis sapinea are ever-present and can be found on the branches of most pine trees with the exception of white pine. Spores can infect without causing symptoms.
2. Use fungicidal sprays.Infection of new shoots may be reduced significantly with properly timed fungicidal sprays. Fixed copper or Bordeaux should be applied twice during the period when buds are opening. Apply in late April to early May, when the buds just begin to open. Repeat application in one to two weeks. Other pesticides registered for use include chlorothalonil (Daconil), mancozeb, and thiophanate methyl (Cleary 3336).
3. Replace with more resistant trees. When dead or dying trees are removed, replant with trees that are less susceptible to Sphaeropsis tip blight such as white pine, spruces, or junipers.
Using an appropriate organic fertilizer would be a viable organic approach to Strategy 1. Of the fungicides mentioned in Strategy 2, consult the Organic Materials Review Institute (OMRI™) for appropriate organic copper products.
|Close-up of dying branch tips on Austrian pine (Pinus nigra) caused by sphaeropsis tip blight of pines