SPHAEROPSIS BLIGHT ( Sphaeropsis sapinea ), also called Diplodia Tip Blight
The fungus which causes Sphaeropsis or Diplodia tip blight may be both saprophytic and pathogenic. It often colonizes plant tissues weakened or killed by other pests, but it may also invade and kill healthy tissues. Although this fungus may colonize many hosts including: red and eastern white pine, Douglas-fir, and Blue, Norway and white spruce, it is a more serious pathogen of Scots and Austrian pines. It rarely attack the others unless they are located near heavily infected Austrian and Scots pine.
Fig. 1. Pine with Sphaeropsis tip blight.
Common symptoms include tip blight and death of low branches. Branch death may be caused by thorough destruction and death of buds and shoots or by lesions. Although it is uncommon, infections which occur where the stem has been wounded can cause girdling cankers which may kill the upper 1/2-3/4, of the tree. Damage from Sphaeropsis resembles many other insect and disease problems. Damage from pales weevil, pine root tip weevil, and spittlebugs can also cause shoot death. Dead, hollowed out shoots may be the result of tip or shoot moth activity, and cankers on trees in the Adirondack region may be caused by Scleroderris.
Infection occurs in the spring when shoots start to grow. The infection may start on a bud or on the newly expanding, succulent shoot. The fungus enters the tree through the needle stomata or through the stem. Small lesions develop which soon enlarge. Buds or shoots that were elongating, stop growing and fade to a pale green or straw color.
To control this disease, try to prevent stresses that may weaken the trees. Also, during dry Autumn days, prune and destroy infected plant tissues such as branches, twigs and cones. Fungicides are available to control this disease where other management practices fail.
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