The first-ever report of the tree-killing invasive insects known as hemlock woolly adelgid (HWA) was confirmed in mid-April by the Indiana Department of Natural Resources in LaPorte County. A concerned homeowner who noticed the distinct small, white, fuzzy insects eating the tree sap at the base of the hemlock’s needles made the report. The USDA Plant Health Inspection Service (APHIS) confirmed that the tree was indeed infested by the foreign insects.
HWAs, which are native to Asia, came to North America in the 1920s. Since that time, HWAs have infested nearly half of the native ranges of eastern hemlock in Appalachia. Named for the cotton covering its body, an HWA resembles a cotton swab attached to the underside of young hemlock twigs; but don’t let its appearance fool you. Within two years, its feeding causes graying and thinning needles. Highly infested trees will stop putting on new growth, look sickly and eventually the whole tree is killed.
“Luckily, the infestation was isolated,” said Philip T. Marshall, state entomologist for the Department of Natural Resources (DNR). “The infestation was located only in a tree planted for landscaping and not in their native territories. This will make it easier to prevent total infestation of our native trees.”
The tree was planted in LaPorte County five years ago, most likely from an infected nursery, according to Tom Swinford, regional ecologist for the DNR.
“The tree may have come from Tennessee, where there has been extensive hemlock infestation,” Swinford said. “What we really don’t want to see is this infestation to run into our substantial native hemlock areas in west and central Indiana.”
HWAs are known to be easily carried by storm winds, but much of the threat occurs from transporting the trees themselves and not taking precautions against infestation, Swinford explained. The infestation has prompted DNR ecological surveys for the next three consecutive summers to track the spread or demise of the infestation, according to Marshall. The DNR is also inspecting the severity of the infestation to determine whether or not there will have to be a full scale hemlock trade quarantine for Indiana.
Hoosiers should be aware of the symptoms of HWA infestations like those who reported the first incident and avoid using hemlock for landscaping.