Iowa using stingless wasps to help control emerald ash borer

Iowa using stingless wasps to help control emerald ash borer

EAB is killing the state's ash trees; to control it Iowa experts are trying something different.

Emerald Ash Borer has been chewing through the state’s ash trees killing a number of them in recent years. To control this tiny insect pest, state officials say they are going to try something different. They are going to release thousands of parasitic wasps.

At Whitham Woods near Fairfield state scientists and insect management specialists think the wasps will lay eggs inside the EAB larvae and inside the EAB eggs. Once the wasps lay their eggs, the eggs start to grow and consume the EAB, and they basically kill off the EAB egg or the larvae stage of EAB. The wasps don’t have stingers. State officials say they are reintroducing the EAB wasp pest to its natural predator.

BAD BUG: Emerald ash borer is a green insect that kills ash trees. EAB has infested 31 of Iowa’s 99 counties, and large areas of the United States. Iowa officials are now beginning to use beneficial insects, a natural enemy of EAB, to attack EAB.

Beneficial insect being released to help manage ash borer

Beneficial insects that will help battle the emerald ash borer, a highly destructive pest of ash trees, will soon be released in Jefferson County in southeast Iowa. State entomologist Robin Pruisner says over the next few weeks several thousand stingless, parasitic wasps will be released at Whitham Woods near Fairfield. This is the first release of the natural enemies of EAB in Iowa.

When EAB was accidentally introduced into North America from Asia, its natural enemies, unfortunately, did not accompany them. This effort is being made to reunite pest and natural enemies to help suppress EAB populations. Following rigorous testing and research one or more parasitic wasp species, native to Asia, have been released in 23 of the 25 states where EAB has been detected. The parasitoids were produced and supplied by the USDA EAB Parasitoid Rearing Facility in Brighton, Mich.

Parasitic wasps won’t be a ‘silver bullet’ for the EAB problem

“Due to the current situation of EAB in and around Fairfield, biocontrol seems justified at this point in time,” says Mike Kintner, the Iowa Department of Agriculture and Land Stewardship’s EAB and gypsy moth coordinator. “The use of biocontrol will not be a ‘silver bullet’ for the problems we face with EAB, but the natural enemies will serve as a long-term management strategy to lessen the impact of EAB.”

The two species of parasitic wasps available by USDA Animal Plant Inspection Service target the larval and egg stages of EAB. Tetrastichus planipennisi female wasps, which are about the size of a grain of rice, lay eggs inside EAB larvae, terminating their development into adult beetles. Oobius agrili female wasps, which are the size of a gnat, lay eggs inside EAB eggs, parasitizing them before given the opportunity to hatch. Both species are harmless to people.

More sites will be approved and used for release of wasps

According to the USDA Forest Service, Iowa has an estimated 52 million rural ash trees and approximately 3.1 million more ash trees in urban areas. State officials say additional suitable sites in Iowa will be approved for release of the wasps used for biological control.

Across the nation, tens of millions of ash trees are dead or in decline because of the emerald ash borer, according to USDA. In Iowa, several cities including Des Moines, Waterloo and Davenport will remove or treat thousands of ash trees in public areas to eliminate possible injury to people or property. Des Moines estimates it will cost about $8.8 million over a decade to remove and treat thousands of ash trees.

More information about USDA’s Emerald Ash Borer Biocontrol Program can be found at

More information about EAB and other pests that are threatening Iowa’s tree population, go to Please contact any of the following members of the Iowa EAB Team for further information on EAB: 

* Mike Kintner, IDALS EAB coordinator, 515-745-2877, [email protected]

* Robin Pruisner, IDALS state entomologist, 515-725-1470, [email protected]

* Paul Tauke, DNR state forester, 515-725-8450, [email protected]

* Tivon Feeley, DNR forest health coordinator, 515-725-8453, [email protected]

* Emma Hanigan, DNR urban forestry coordinator, 515-725-8454, [email protected]

* Jesse Randall, ISU Extension and Outreach forester, 515-294-1168, [email protected]

* Mark Shour, ISU Extension and Outreach entomologist, 515-294-5963, [email protected]

* Laura Jesse, ISU Extension and Outreach entomologist, ISU Plant and Insect Diagnostic Clinic, 515-294-0581, [email protected]

* Donald Lewis, ISU Extension and Outreach entomologist, 515-294-1101, [email protected].

* Jeff Iles, ISU Extension and Outreach horticulturist, 515-294-3718, [email protected].

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