Diplodia (Sphaeropsis) Blight
This disease is caused by the fungus Diplodia pinea. The blight occurs on many 2 and 3 needle pines and some other conifers.
The fungus attacks young, healthy, unwounded needles of new candles. However, on stressed evergreens, twigs may be attacked. Since the fungus increases inoculum on old dead cones, trees thirty years and older are more likely to be attacked. Young trees severely stressed or growing near old infected trees may also be attacked. Browning, stunting, and twisting of new shoots and needles are the first symptoms. One side of a tree or the lower part may be the first area affected. During wet springs, every branch may have brown tips. A brown discoloration starts at the base of needles and grows toward the tip. Needles die by the time they are one half to three fourths normal length. Sometimes needles curl and twist. Infected stems often result in droopy candles (new growth). Resinous cankers may appear on stems at the youngest branch whorl or base of blighted needles. Resin from infected areas may cause dead needles to stick to the tree. Large resinous cankers may occur on older branches where wounds occur. Winter injury is a common site of branch infection.
This disease can be can be confused with low temperature, drought, winter drying or Nantucket pine shoot moth damage. Infection may occur in a few hours when temperatures are between fifty-three and ninety-six degrees fharenheight with at least twelve hours of moisture.
Management of the disease requires that all affected twigs and cones be removed. Fertilize trees stunted by the disease to stimulate vigorous growth. Fungicide sprays are recommended in conjunction with cultural controls. Three sprays are necessary: one at bud break, half candle elongation, and full candle elongation. Contact your local university extension office, garden center or arborist for the proper fungicide to use. Effectiveness of the treatments and severity of the disease are affected greatly by the weather conditions at the time of shoot emergence. Maintain healthy plants and good sanitation.
Written by James Schuster, Retired Extension Educator, Horticulture & Plant Pathology, and reviewed by Nancy Pataky, Retired Extension Specialist, Plant Pathology, Department of Crop Sciences University of Illinois at Urbana-Champaign.
Filed under plants: Evergreen Trees & Shrubs
Filed under problems: Fungal Disease