NORTH KINGSTOWN — As gypsy moth populations wane, the Rhode Island Department of Environmental Management is warning that there are plenty of new pests waiting to take their place.
At a Nov. 4 workshop presented in North Kingstown by the DEM's urban and community forestry program and co-sponsored by the Rhode Island Tree Council, tree care and landscaping professionals learned about existing and emerging threats to trees in Rhode Island and throughout New England.
Nancy Stairs, cooperative forestry program supervisor at the DEM, said the purpose of the workshop was to get the latest information to the people who work with trees.
“We want to get more information out to our tree wardens and our licensed arborists and people carrying out the work in the state, providing them with some professional information and updates,” she said.
Rhode Island Tree Council technical advisor John Campanini said he hoped that getting the information to tree care professionals would raise the overall level of awareness of current and future pests.
“It’s good to get this information out especially since, I think, in the future, the threat of random weather events is going to spark a lot of these insect and pest problems,” he said. “So it’s good to get everyone on the same page with regular information getting out to the public and especially the people that are working in these arenas.”
Weakened by repeated drought, trees have been more susceptible to invasive insect pests, such as the gypsy moth, which devastated swaths of oak trees throughout Rhode Island, Connecticut and Massachusetts. After repeated defoliations by gypsy moth caterpillars, hundreds of thousand of oaks succumbed, leaving the state, the towns and electric utilities to bear the considerable expense of removing them.
Stairs presented gypsy moth data collected by DEM forest health coordinator Paul Ricard, who conducts aerial surveys of Rhode Island’s forests to assess tree damage.
“This is what it looked like last year for the mortality,” she said, pointing to a map. “You can see there are pretty broad swaths of it, mainly caused by gypsy moth.”
This year, however, the damage will be considerably less severe, partly due to a fungus that killed many of the caterpillars last year. Surveys of gypsy moth egg masses, which are deposited on tree bark, also show a decline in populations since the peak of the infestation in 2016.
In recent years, winter moth, gypsy moth and to a lesser extent, autumn webworm, have been concerns. Now, the most immediate threats are a beetle called the emerald ash borer and the spotted lanternfly.
Emerald ash borer was first detected in Michigan and Windsor Ontario in 2002. Spreading quickly, it had killed ash trees in 35 states from Maine to Texas by the end of 2018. In Rhode Island, ash trees account for less than 4 percent of forest species, but they have been widely planted as street and specimen trees. Emerald ash borer has been found in Westerly and Hopkinton as well as Burrillville, Lincoln and Providence.
Stairs said cities and towns need to decide what to do about their ash trees and allocate funds for treating or removing the trees.
“If you have any historical trees or trees of particular value or trees in certain areas of ash where we would like to do some prophylactic treatment with Emamectin,” Stairs said. “Do we have some trees that we should just take down because we know they’re already in poor shape.”
Another major threat is the Spotted lanternfly, an insect native to China, India and Vietnam that was first found in Pennsylvania in 2014 and has spread to New Jersey, Delaware, Virginia. It has also been detected in western Connecticut.
Cynthia Kwolek, Senior environment planner with the Rhode Island Division of Agriculture, explained that lanternfly egg masses are easily spread on shipping pallets or the undersides of vehicles.
“It might be something that’s easily overlooked when shipping goods,” she said. “It can also be found on stone, on smooth, manmade surfaces like vehicles or trailers, boats, all kinds of different things.”
Lanternfly nymphs have damaged apple trees and decimated grapevines.
“Vineyards in Pennsylvania have seen reductions of 80 to 90 percent of their yield. That’s since 2014,” Kwolek said. “There’s been a threefold increase in frequency of insecticide applications, so that’s incredibly costly.”
Heather Faubert an entomologist at the URI plant clinic who helps commercial growers identify and control pests, presented an overview of expected plant pests in 2020.
Bagworms, Faubert said, would continue to kill arborvitae and other conifers like junipers.
“Now, they’re really getting established and this year there’s a bumper crop of bagworms,” she said.
Ambrosia beetles implant a fungus inside trees, which the beetle larvae then feed on. Boxwood blight, a fungal disease, has been killing boxwoods in Rhode Island since 2011. Other threats include cedar apple rusts, Japanese apple rusts, walnut lace bug, and fall webworm.
One recent success, Faubert said, was the introduction of parasitic flies to control winter moth, which began attacking trees in Rhode Island in 2005 and continued to defoliate them until 2016.
“Working very closely with the University of Massachusetts, we were releasing a fly, a fly that parasitized only winter moth, Cyzenis albicans,” she said. “So we released this fly in eight locations in Rhode Island between 2011 and 2017 and so between the fly and other natural predators just building up over time, winter moth is not much of a problem.”
The urban forestry workshop, Stairs said, would probably become an annual event.
“People still need to be up to date and get refreshed and sometimes, it’s things they know, but then they can feel good about knowing what their job is and other times, they find out something new,” she said.