Minnesota is counting on a ground-nesting wasp known as the smoky winged beetle bandit to detect new locations where ash trees are coming under attack from the emerald ash borer.
Starting this summer as part of a $447,000 state government program, more than 100 citizen volunteers in at least 17 counties will search for colonies of the beetle bandits or spy on sites where the wasps are known to forage for bugs in trees. By netting the wasps or staking out their nests, volunteers will gather samples of beetles that the female wasps prey upon to feed their offspring.
In Connecticut and elsewhere, the wasps have tipped off researchers to new infestations of emerald ash borers, one of the most destructive non-native pests in North America. Such early detection efforts are vital to curbing the bugs in a state where about 1 billion ash trees are susceptible to killing by infestation, program leaders said.
“We’ll be watching one insect to discover another,” said Jeff Hahn, an entomologist at the University of Minnesota. “It’s another tool in our arsenal.”
Minnesota Wasp Watcher program coordinator Jennifer Schultz said a network of trained volunteers will allow the state to cover more ground in its surveillance of the spreading ash borer. The insect first arrived in Minnesota in 2009 and is now found in eight counties: Anoka, Dakota, Fillmore, Hennepin, Houston, Olmsted, Ramsey and Winona. Wasp watchers have documented a new infestation near Rushford in Fillmore County.
In Michigan and Ohio, ash borer infestations have killed 99 percent of all ash trees within six years of initial infestation. By comparison, the ash borer has killed off very few trees in Minnesota, but cold weather hasn’t stopped the bugs from spreading, according to a summary of the project written by agriculture officials. Funded by a grant from the Environment and Natural Resources Trust Fund, the project was proposed by the Department of Agriculture and U Extension Service.
Schultz said the sooner state scientists can detect ash borer infestations, the easier it is to slow them down with tree removal, quarantines and other management practices. One of the control measures is to release a different species of wasps that kill ash borer larvae.
“Minnesota is faring fairly well … but we have to be very proactive,” Schultz said. “Early detection allows for better management.”
The smoky winged beetle bandit wasp is native to Minnesota and is about the size of a yellow jacket. The insects are docile around humans but sting tree-tunneling beetles into a state of paralysis before hauling them back to the nest. When netted, the wasps drop their prey.
Schultz said underutilized baseball diamonds are ideal sites for the wasps to congregate. The insects are solitary nesters but flock together in hard-packed, sandy soil environments — often located near human activity.
One goal for the wasp watchers is discovering how far north the beetle bandits will nest. Currently, the northernmost sites known to the program are in Ham Lake and Andover.
Current funding should carry the program through mid-2017, but organizers will likely seek to extend taxpayer support. Besides targeting the emerald ash borer, the wasp-watcher program also will screen for other unwanted insects. One of those high-risk, tree-killing beetles is the European oak borer. It hasn’t been detected in Minnesota, but it has been picked up on a trap in Michigan and detected with biosurveillance in Ontario, according to an outline of the wasp-watcher program.
“If it’s there, we want to know about it,” Schultz said.