White Pine Needle Disease Generates Concern
State officials cite wet weather as a key factor, urge caution before thinning
AUGUSTA – Maine Department of Agriculture, Conservation and Forestry officials have received numerous calls recently regarding the extensive early “casting” of white pine needles. Callers have stressed that the white pine crowns of affected trees have turned from the dull winter green to a yellow-straw color and then quickly to tan and brown. Heavy rains resulted in the near complete removal of the affected needles from the trees, leaving crowns appearing thin. With many trees now having only the current-season needles left to photosynthesize, concerns have been raised prompting this informational bulletin from the Department.
White pine needle-drop condition
The white pine needle disease epidemic has been occurring in Maine, and in most other areas of New England and New York, for at least eight consecutive years. Above-average spring and summer precipitation patterns experienced in the Northeast for the past decade are believed to be a primary factor in facilitating needle infection, caused by the development of one or more of several pathogenic fungi.
Fungi infect needles early in spring and develop through the needles during summer and fall. The following year, when the weather warms, the symptoms on the infected one-year-old needles first appear during early to mid-June. The progress from symptom development through needle casting occurs over a very short period of time – usually about three or four weeks. The symptoms appear as a rapid flare-up of needle yellowing and casting, which has occurred throughout Maine over the past two weeks. This year, trees continue to show weakening due to the stress caused by the reduction in foliage and photosynthetic efficiency.
What is being done to address this?
State Foresters are collaborating with neighboring states and with the U.S. Forest Service to determine the scope of the problem and identify solutions. In Maine, a survey of damaged trees is currently underway and results will be compared with defoliation estimates from previous years. Early indications are that the severity of disease is similar to that in past years, but that the long-term effect of many consecutive years of the loss of the one-year-old needles has weakened some trees to the point where mortality is now occurring. Other secondary insect and disease problems have also appeared in many stands where sustained and severe damage from the needle disease complex has occurred, but these effects are not yet well-understood. It appears that for the foreseeable future, white pine will be another threatened resource unless the needle disease epidemic abates, either from a break in the weather and moisture patterns, or from some other as yet unknown reason.
What can you do?
Control or management recommendations are limited, but state foresters urge caution before conducting thinning operations. As this season progresses, current-season foliage will develop that will help to “mask” the thin appearance of the crowns. Heavily infected stands and trees in stands where mortality is believed to be the result of needle diseases may be salvaged. Thinning efforts need to be carefully considered, as thinning operations may cause additional stress and result in an increase in mortality and stand collapse. In the meantime, landowners should consult with a professional before thinning operations.
Who can you contact?
Woodland owners are encouraged to contact their licensed forester to help assess the actual impact of the blight on their woods. For yard and ornamental trees, contact a licensed arborist. If you need help finding a resource professional, contact the Maine Forest Service at 1-800-367-0223 (in state) or (207) 287-2791.
For more information about the Maine Department of Agriculture, Conservation and Forestry, go to: http://www.maine.gov/dacf/