Chris Hastings expected to give his clients a “slam dunk” when he sold them on applications to treat hemlock woolly adelgid in the southwestern North Carolina mountains. The results over the last three years, however, have been more like a jump shot that bounces around the rim keeping the shooter and spectators on edge before finally falling in the basket.
As a result, Hastings, a board certified master arborist, shares his experiences with other tree care professionals, as he has done at several arborists meetings on hemlock woolly adelgid (HWA) throughout the region. “I’ll give away the bank,” he says, addressing about 20 tree care professionals at a Valent Professional Products-sponsored event in Highlands, N.C., on May 17. “I believe this is an important issue and there are enough trees for us all to work on.”
HWA entered the Pacific Northwest in 1924. In the 1950s the pest was introduced to the eastern U.S., most likely by way of nursery stock or birds, says Joe Chamberlin, entomologist and field market development specialist for Valent Professional Products, Walnut Creek, Calif. The pest is difficult to control because it has no natural predators in the U.S. Currently, officials are investigating the use of predatory beetles as a biological control to HWA.
HWA invaded the western North Carolina mountains about five years ago. There are several reasons this pest so difficult to control here, Chamberlin says, including lower winter mortality than northern regions and the enormity of the hemlock population in the Nantahala National Forest.
About three years ago after working for a national tree care company, Hastings started his own business, Alpharetta, Ga.-based ArborMedics. Several of Hastings’ Atlanta clients have second homes in Highlands and Cashiers, N.C. These resort towns, like many others in the southern crest of the Blue Ridge Mountains, are plagued by the presence of HWA, an Asian fluid-feeding insect that feasts on Eastern and Carolina hemlock trees throughout the eastern United States, causing the trees to lose their needles, turn a sickly gray-green color and die in about five to 10 years.
About three years ago, one of Hastings’ Atlanta clients told him he received a $1,000 quote to treat a 75-foot tall tree with soap and horticultural oils, which is originally the method state extension agents recommended. The cost was so high because the company would need to bring in a bucket truck to perform the application, which required excellent coverage for efficacy. Curious about why no one recommended a $150 pesticide treatment, Hastings traveled to Cashiers to talk with his client’s property owners’ association.
This POA had a unique challenge. Due to preservation standards in the community, located at the world-class Wade Hampton Golf Club, homeowners aren’t permitted to cut down trees unless they’re dead. Many homeowners’ hemlocks weren’t dead yet, but were heading that way after several years of HWA infestations. In addition to strict preservation standards, many of the homeowners were personally interested in saving their trees, as the beauty of the landscape was their reason for purchasing a home in this area of the country in the first place. Losing the hemlocks one by one would likely begin to affect the entire ecology of the area. For example, the death of shade-providing hemlocks would cause the temperature in the rivers and streams to rise, killing off trout populations and trickling down to the rest of the aquatic species, says David Bates, executive director of the Jackson-Macon Conservation Alliance, an environmental organization based in those two counties.
After speaking with the Wade Hampton POA, Hastings contracted with the association to treat hemlocks within 10-feet of the community’s common road and he was also hired by other homeowners to treat sickly hemlocks on their individual properties.
LESSONS LEARNED. The first year Hastings treated, he completed basal drench imidacloprid applications in August, and returned in late fall to evaluate his work. The white “fuzz” indicating the adelgid nymphs resumed development was present, and Hastings was left with what he calls a “customer service nightmare” because the clients could also still see the woolly substance that gives the pest its name. For the next year, Hastings was on edge, afraid he’d overpromised his service capabilities. He constantly reassured clients that the treatments were working, but it was taking a long time for the trees to react to the pesticide and to resume new growth.
Hastings wasn’t scamming his customers – about 90 percent of the treatments were in fact working. He often climbed to the top of clients’ trees to bring them down samples that proved new growth was occurring. While many of the trees had some new growth at the very top, many of the lower boughs were slow to react and a lot trees required extensive pruning, which thinned them out considerably and created an added cost that Hastings hadn’t prepared his customers for. But more critically, these weren’t the graceful, magnificent hemlocks his clients remembered. “It was working, but I was struggling with the impression of failure. Even if I killed all the adelgid, it still takes as many as five years for the tree to come back.” he says.
After coordinating studies in the region with University of Georgia entomologist Kris Braman, Hastings began using a systemic insecticide with the active ingredient dinotefuran, which is a neonicotinoid.
Imidacloprid works, Hastings recognized; however it’s effective for smaller landscape trees and high sunlight conditions. The dinotefuran-based product works quicker on the massive hemlocks in shadier, forested areas due to its high level of water solubility, which theoretically means there will be more root uptake and faster transport in the vascular system.
His cost for Safari, the dinotefuran product he uses, is $1.50 per diameter inch (he spends about $300 per $3-pound jug of material, which he uses at a rate of 42 ounces per 100 gallons).
Today, most of the trees Hastings has treated are clean and he’s now just monitoring these trees. Now Hastings isn’t concerned about residual adelgid outbreaks. Instead, he's keeping on eye on them in case of spider mite outbreaks or reinfestation. He recommends that tree care professionals consider following up HWA treatments with a monitoring service for about $75 or $100 per trip.
After several years of trial and error, these results are much closer to the slam dunk Hastings hoped for during his first trip up the mountain.