Brown Needles on White Pine
White pines with brown foliage have been more common than normal in 2007. The most common problems are conspicuous, but not serious. Most of the affected trees are likely to recover.
Brown Spot Needle Blight is the most common disease this spring.
Symptoms: At this time, only old needles are brown. The new needles, produced on shoots this spring, are green and healthy. The heaviest browning is usually on the lower branches. In a group of white pine trees, some may have a lot of brown needles, while others are mostly green.
Cause: This disease is caused by a fungus. Like many fungus diseases, the foliage is infected when it is growing in the spring, during wet weather. We have had several years with wet springs, so this disease has been building up. With some moist spells this spring, as well, we will probably see this disease again in 2008.
Management: Brown spot needle blight is seldom serious to tree health. Control is rarely necessary, since brown needles fall off the tree by early summer. This should make the trees look a lot better, although the foliage may be thin. Spacing trees improves air circulation around them, and reduces moist conditions for needle infection. Collecting and removing fallen needles may be helpful around landscape trees.
Pine Leaf Adelgid
Symptoms: Affected white pines have dead shoots from top to bottom of the crown. The dead portion is about 4" long, and brittle.
Cause: Pine leaf adelgid is an insect that alternately feeds on pine and spruce. As described in the Maine Forest Service newsletter, “The adelgids have a complex life cycle that takes two years to complete with two hosts, white pine and spruce - both red and black . The adelgids form galls on the tips of spruce branches that resemble cones during the first year. In the second year of the life cycle the adelgids feed on pine branches. Winged females line up on needles and lay eggs in June, then die and remain attached through the summer so their presence would indicate a continuing infestation. Young pine can be killed by heavy infestations while older trees may have branch dieback.”
Management: Because the insects that caused the damage to pine are now on spruce trees, no additional pine shoots should be damaged this year. This gives the trees a chance to recover naturally.