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New Weapon in Emerald Ash Borer Detection Found

A type of wasp has been found to be effective as an early warning device for Emerald Ash Borer infestation.

The partnership of the Morton Arboretum and Illinois Parks and Recreation Association has discovered a new predator in the fight to stop the Emerald Ash Borer (EAB). Researchers confirmed that Cerceris fumipennis (Cerceris), a native wasp that preys on EAB, was found at Emerson Park in suburban Skokie. Now, researchers hope that the wasp will serve as a sort of “canary in the coal mine,” or an early warning system for EAB infestation, in areas where EAB has not yet been found, said Dr. Frederic Miller, research associate at the arboretum.

“By the time humans are able to detect EAB visually, the infestation is usually well-established. We hope this wasp will serve as an effective monitoring tool, giving us an earlier read as EAB makes its way across the country,” he said.

Researchers hope that earlier detection will help communities’ better control and manage infestations.

Cerceris wasps nest in the ground, commonly in open areas of hard-packed sandy soil with ash trees nearby. Athletic fields, such as ball diamonds, volleyball courts, horse shoe pits, and even parking lots are common nesting locations. The nests are characterized by pencil-diameter holes on top of little mounds of sand. The wasps are most active during summer months, when they feed on a whole family of wood-boring insects called Buprestid, of which EAB is a member, said Devin Krafka, research assistant at the arboretum.

“Cerceris is a parasitic wasp. It goes out to find a buprestid, or a wood-boring insect like EAB, stings it and brings one back to its nest. Later, it will lay an egg on it and place it in its own chamber. When the egg hatches, the larva will eat the beetle,” Krafka said.

To help in the hunt for the wasp, The Morton Arboretum set up a new "biosurveillance" program. The Cerceris Identification and Awareness program (CIA for EAB) enlists the help of park district staff and park users to look for wasp nests and EAB carcasses near them. The Cerceris wasp is a good candidate for this pilot program, because it doesn’t harm humans. This new program asks the community to be "citizen scientists" to help fight invasive pests.

“We need park professionals and residents to watch ball fields for signs of ground-nesting wasp activity or the actual nests,” said Edith Makra, Community Tree Advocate at the arboretum, who leads the CIA citizen science effort. “We first need to locate and confirm the presence of Cerceris so that we can enlist citizen scientists in future monitoring that can help manage EAB to protect ash trees.”

Once park districts alert the arboretum about possible nests, Krafka and other research assistants will confirm they belong to Cerceris wasp. This was the case in Skokie. John Gacki, parks supervisor for the Skokie Park District, noticed nests and colonies in the ground when doing work on the baseball field. He immediately contacted arboretum and that’s when Krafka went to check it out.

“First I saw it flying around, and identified it visually,” Krafka said, “Then I saw the dead EAB carcasses on the ground.”

The Cerceris is different from the Oobius wasps the city of Chicago recently released to fight EAB. Cerceris is native to the area and can thrive in the environment here. Tiny, almost invisible, the Oobius wasps are from China. Federal officials introduced Oobius wasps in hope they will reduce the number of EAB in the city. Whereas researchers hope Cerceris, a much larger wasp easier for biosurveillance, will help them locate EAB infestations early.

Scientists never really paid attention to Cerceris since the 1800s. It wasn’t until it was discovered that the bugs preyed on EAB that the insect was back on their radar. Across the northeastern U.S., from Minnesota down to Missouri, east to the Atlantic Coast, researchers are on the lookout for the wasps. As the local leader in this national effort, arboretum staff discovered Cerceris Illinois this summer.

As of now, EAB has only been found in northeast Illinois, as far west as Winnebego County, and as far south as Champaign and Vermillion Counties. But people are bracing for the first discoveries of EAB further south and west in the state of Illinois. The discovery of the Cerceris wasp could help communities not yet affected by EAB early detect a potential infestation.

EAB is native to Asia and is suspected to have arrived in this county in cargo utilizing wood packing material. In its native range, EAB attacks and kills trees that are weakened by stresses such as drought, disease, and mechanical injury. Unfortunately, in North America, EAB also attacks and kills healthy trees. This invasive pest is so aggressive that virtually all ash trees are at risk, and trees may die within two to four years after they become infested. Already, tens of millions of North American ash trees have succumbed to this borer. If EAB is not contained, the devastation to our ash trees may be similar to that of  American elms, which were decimated by Dutch elm disease. The potential impact from EAB in Illinois is significant. Ash trees account for 6 percent of forests statewide, and 20 percent of residential trees in the northeastern part of the state, or approximately 130 million ash trees.

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