Western North Carolina is seeing the effects of two forest pests that appear to have no plans to take summer vacation.
Most years, native forest pests munch on trees, never really causing huge disturbances or widespread damage. Natural enemies, environmental conditions, and interactions with the host plant generally keep populations low. But every once in a while, when environmental conditions are perfectly-suited, pest populations build and an outbreak can occur, catching everyone by surprise.
“Oaks in Western North Carolina, particularly red oaks, are losing leaves as a result of oak leaf blister, a disease caused by a fungus,” said Agriculture Commissioner Steve Troxler. “In addition, foresters are reporting damage from yellow-poplar leaf mining weevil, which is causing widespread browning and defoliation on yellow-poplar trees.”
Oak leaf blister, a disease caused by a fungus, is affecting the appearance of oaks across the western region. White and red oaks are both susceptible, but it is more common and severe in red oaks. When infected, leaves develop light green, yellow or white spots. As the disease progresses, the spots form yellow or brown puckered lesions or blisters. When the infection is severe, the entire leaf yellows, curls and drops prematurely.
“Oak tree leaves will have light green, yellow or white leaf spots. As the disease progresses, the spots form yellow or brown puckered lesions or blisters,” State Forester David Lane Lane said. “When the infection is severe, the entire leaf yellows, curls and drops prematurely.”
Most years, oak leaf blister is minor and outbreaks are typically associated with a cool, wet spring, and chemical control is not needed. The disease only affects the leaves and, as with most defoliating pests, a single year of defoliation will not affect the long-term health of the tree. To keep damage to a minimum, landowners are encouraged to maintain general tree health, such as watering during dry periods.
The yellow-poplar leaf mining weevil is also in outbreak status, causing widespread browning and defoliation on yellow-poplar trees. This beetle is damaging to yellow-poplars, magnolias and sassafras trees. As a result of adult and larvae feeding on the leaves, the leaves turn brown and die.
Most years, the weevil is not considered a threat to yellow-poplar timber. Sporadic outbreaks have been recorded in the Eastern U.S. since the 1960s when outbreaks similar to the ones being seen now caused significant foliage loss on yellow-poplar in the Appalachian Mountains. Foliage destruction temporarily reduces the aesthetic values of landscape trees. To manage the pest, promoting general tree health is best. The outbreak should subside on its own, especially with the help of natural enemies.