DNR scrutinizes widespread browning of pine needles
Widespread needle tip browning on red pine has been observed for the second consecutive year across much of the upper Great Lakes region. No tree mortality has been associated with the condition, but the Wisconsin Department of Natural Resources (DNR) is monitoring it. The condition is heavier in some places than others, but once in a stand or location, it tends to be evenly distributed.
For trees with the condition, needle tip browning is common on the lower half of mature red pine crowns. On two- to three-year-old needles, the outer half to three-quarters of the needles appear reddish brown to straw-colored while needle bases remain green. Black or dark brown bands and spots are often present on needle tips. Lower crown thinning is also common on affected pine.
Newly impacted needles will gradually lighten in color from reddish brown to straw-colored as dead needle tips dry out through the growing season.
Causes and potential impacts of this needle tip browning were investigated by the DNR last year, but no conclusion was reached.
At present, there is not enough information available to determine whether this region-wide episode of red pine needle tip browning is caused by wet weather aggravating one or several needles diseases, weather-related tissue injury or a combination of both. Loss of needles in the lower crown due to this condition will likely reduce leaf area and productivity and may lead to tree stress over time. Follow-up monitoring this season will hopefully provide additional answers on potential causes and impacts on tree health.
Residents are asked to report red pine needle browning to their local DNR forester and regional forest health specialist so the extent of this condition can be tracked. This information will help determine if sites should be further evaluated for forest health considerations.
Paul Cigan is a forest health specialist with the Wisconsin DNR, working out of Hayward.