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Thwarting tree damage from fall cankerworms requires diligence, annual effort

In a file photo, cankerworms climb an oak tree in Edgehill Park just across the street from trees that have been banded in resident’s yards in the 800 block of Edgehill Road North.
In a file photo, cankerworms climb an oak tree in Edgehill Park just across the street from trees that have been banded in resident’s yards in the 800 block of Edgehill Road North. jsimmons@charlotteobserver.com

Fall cankerworms are again poised to make their annual appearance in Charlotte, forming a chow-line for area hardwood trees.

The females lay their eggs on branches and twigs where caterpillars hatch in the spring. They feed on emerging leaves, weakening trees and making them more susceptible to stress, drought and disease.

“The mature females are actually tiny wingless moths that ascend trees after the first hard frost, usually in late November or early December,” said Donald Booth, who recently retired as research entomologist with Bartlett Tree Research Laboratory in Charlotte.

Their target is usually oaks. But they are also seen in maples, dogwoods and fruit trees such as crabapple and cherry, Booth said.

We are particularly concerned this year as we experienced some defoliation with the drought. Additional defoliation this upcoming spring would mean extra stress, and we want to avoid that.

Erin Oliverio, tree canopy program manager for the city of Charlotte

The cankerworm population has continued to grow for the past three decades, city arborists say. The city began aggressively managing the population in 1992 with banding and aerial spraying using a biological pesticide, spraying twice more in 1998 and 2008. Charlotte’s large willow oak population may help promote the infestation, according to the city.

Booth has another theory: urban growth has caused a decline in the Fiery Searcher Beetle, a cankerworm predator.

“This large, green beetle with enormous jaws is the T. rex of cankerworm predators,” he said. “It thrives in forest-like environments, where decaying trees and leaves are their preferred habitat. They simply devour cankerworms.”

Residents can help support the beetle population by mulching around trees, Booth said. “Don’t have them exterminated,” he said.

Shortage of prevention treatment

Adding to this year’s challenge is a shortage of one popular prevention treatment method. Tanglefoot, a brand of sticky tree-banding material, is used as a barrier to trap cankerworms as they climb up the trees.

Wade Goode, manager of lawn and garden supplies at Blackhawk Hardware in Charlotte, said Tanglefoot banding kits are already sold out. He expected the limited supply of 1- and 5-pound tubs to be sold out shortly.

“We are trying to find an alternative to Tanglefoot,” Goode said.

He said Tanglefoot’s manufacturer was sold and the material might not be available until next year. Blackhawk hopes to have a similar product from TreeKote available by Thanksgiving.

Another popular tree banding alternative, BugBarrier tree band, is available locally at Southern Organics in Monroe. A spokesperson said last week the store had a limited supply of 30-foot kits available. They anticipated a replenished supply by Nov. 20.

People should be cautious about banding too early, before all the leaves have fallen. Leaves can adhere to the bands to form a bridge that gives the cankerworms a barrier-free pathway to higher branches.

Erin Oliverio, tree canopy program manager for the city of Charlotte, said the city has contracted to have 5,500 street trees banded this year, beginning the week of Thanksgiving.

“We are particularly concerned this year as we experienced some defoliation with the drought,” Oliverio said. “Additional defoliation this upcoming spring would mean extra stress, and we want to avoid that.”

Oliverio noted areas along Wilkinson Boulevard, South Boulevard, Eastway Boulevard and Sugar Creek Road showed the largest level of cankerworm infestation this past spring.

“It is unpredictable from year to year,” Oliverio said. “We encourage homeowners to band especially their larger trees.”

An effective alternative to banding involves spraying in the spring after the emergence of the caterpillars, Booth said. It would cost $150 to $300 to spray a large oak, he said.

Cankerworm event

The Charlotte Chapter of the North Carolina Wildlife Federation (CROWN) is hosting a free community program discussing cankerworms. Tree expert Patrick George with Heartwood Tree Service will lead the discussion and answer questions. Go to http://bit.ly/1SgYh2B for a list of retailers with tree-banding supplies.

When: 7 p.m. Thursday.

Where: McClintock Middle School, 1925 Rama Road.

Details: www.crowncharlotte.org.

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