Durham News

June 27, 2014

City, Duke ask help to combat cankerworms

Chronic infestations of cankerworms, a.k.a. inchworms, pose a threat to the willow oak trees that line many of Durham’s inner-city streets and grace the Duke University campus. So, the city and Duke University are organizing a “cankerworm initiative” to fight the pests and hope Durham residents join in.

DURHAM Chronic infestations of cankerworms, aka inchworms, threaten the willow oak trees that line many of Durham’s inner-city streets and grace the Duke University campus.

“It is a mess. It is a frightful mess,” said Alex Johnson, the city’s urban forest manager.

So, the city and Duke University want to do something to combat the worms. They’re organizing a “cankerworm initiative” to start in September and looking for Durham residents to join in.

“As responsible neighbors, we want to make sure we keep our city beautiful,” said Katie Rose Levin, the university’s natural resource manager.

The willow oaks that predominate neighborhood street trees were planted in the 1930s. They are nearing the end of their natural lifespans which are shortened by stress elements of their urban environment such as car exhaust and restricted space for roots to grow.

Cankerworms add another stress that helps kill the trees prematurely, for willow oaks are their favorite places for adults to lay eggs and for the young to feed. Their feeding may not kill the tree outright, Johnson said, but repeated defoliation is “like a death by a thousand cuts, one more nail in the coffin” and can lead to other problems.

“Like falling over,” he said.

Levin showed a map with locations marked of dozens of trees on and near East Campus that the worms defoliated last year.

“Worms up here are going to blow into neighborhoods over there,” she said. “It really is kind of a community issue.”

The initiative plan is to disrupt the worms’ reproductive cycle with sticky “bands” around the trees.

“The females are the ones we want to get,” Johnson said, explaining the plan at last week’s InterNeighborhood Council meeting. “They can’t fly and they get stuck, and if they get stuck before they lay eggs then we don’t get eaten.”

Other than banding, he said, the only control option is spraying with an organic insecticide, which kills benign insects and can poison songbirds that eat sprayed bugs or worms.

Some neighborhoods began banding programs last year, inspiring the idea for a wider-spread program. But Durham and Duke have thousands of willow oaks. Hence the appeal to spread word of the initiative through neighborhood organizations.

The initiative is still in an organizing stage, but Levin said the plan is to hold an information workshop for the public in September, make up banding kits in October, band trees in November and apply the glue in December in time for the fall worms’ emergence in late fall and early spring.

In April, Levin said, they’ll “take the trash off our trees” – because bands left on too long hold moisture against the trees’ surface, creating a friendly site for other infection, Johnson said.

Cankerworms are a native species to North Carolina, he said, but they have become a particular problem only in recent years.

Previously, Johnson said, migrating songbirds “graciously” kept the worm population in check, but changes in the seasonal weather cycles, such as springtimes arriving earlier than in years past, have thrown the worms’ emergence and the birds’ migration out of sync.

“We can’t really expect nature to figure this out and solve the problem for us,” Johnson said. Unfortunately, cankerworm control is going to be an ongoing endeavor.

“It’s like ticks; you stay vigilant,” Levin said.

It may be hard to get excited about worms, Levin said, but Mike Shiflett, an INC delegate from Northgate Park, pointed out that they’re not just a problem for trees. As they proliferate, they come indoors.

“You crawl in bed with your wife and you find a cankerworm crawling on her or on you, you get excited for another reason,” he said. “If they’re making it into your bedroom, they’re making it into your kitchen.

“If they’re not in your neighborhood, they’re coming,” he said. “It is gross.”

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