by Elizabeth A. Tomlin
“An accurate diagnosis is key to solving problems on tree farms,” emphasized Brian Eshenaur, Plant Diagnostician, Plant Pathology, Senior Extension Associate for the New York State Integrated Pest Management program with Cornell University.
Eshenaur, along with Dr. Elizabeth Lamb, New York State Integrated Pest Management Program/Horticultural Specialist, Cornell, and Lily Calderwood, Commercial Horticulture Educator, Cornell, presented an updated program on Balsam Woolly Adelgid and other Christmas tree diseases recently.
Lamb described Hemlock Woolly Adelgid (HWA) as an aphid-like invasive insect native to Asia that is now presenting a serious threat to forest and ornamental hemlock trees in the Midwest and Northeast. It is recognizable by the white “woolly” masses of wax that are about half the size of a cotton swab. They are produced by females in late winter and are visible at the base of hemlock needles throughout the year, even after the adults have died.
“They look like they are ‘flocked’,” Lamb commented.
The insect that targets Eastern and Carolina hemlock trees has been reported to have severely damaged some sites with losses of up to 90 percent of saplings and 50 to 69 percent of total stand density.
HWA is spread by wind, birds, humans or other animals and reproduce twice yearly. Lamb noted that no males are produced; all are female and reproduce asexually.
The disease is active during the winter, allowing it to avoid summer predators and allowing it to sap hemlock’s increased winter energy intake.
The tiny black insect lives and feeds on the hemlock. Once eggs hatch, nymphs move to new needles and attach themselves to the base, feeding from starch reserves and nutrients, causing needles to dry up and fall off and preventing growth. Hemlocks with the disease may live up to 20 years before death.
Cutting and moving the tree can cause the spread of the insect to other trees.
If you notice white, waxy material at the base of the needles on hemlock trees do not remove potentially infested material from the site in an effort to prevent the spread of HWA. Take photos, note the location and report to the Midwest Invasive Species Information Network online reporting tool at .
Beneficial insects are being investigated for controlling these diseases.
Lamb reported that due to pollinator issues, there are potential possibilities for “pollinator habitats.”
“Christmas tree growers are good stewards of the land,” commented Lamb. “There is so much interest now in pollinators.”
Due to the new diseases related to ticks, the IPM team advises growers to “keep the grass down” in tree lots, especially where folks are coming in to cut trees themselves. “There is a renewed interest in people cutting their own Christmas trees,” said Lamb.
Eshenaur spoke about root rot in their nursery stock. “There are a couple important root rot diseases that can be a problem,” Eshenaur said. “In order to take action and head off future problems it is important to know which one you have.”