09-29-14 CDA News: Biological Control Enlisted to Help Manage Emerald Ash Borer in Colorado…

CEABRT-CO Emerald ASh Borer Response Team logoTetrastichus adult wasp-APHIS Tetrastichus larvae under bark-APHISBOULDER, Colo. – Stingless, parasitic wasps that target and kill emerald ash borer (EAB), a highly destructive tree pest that poses a serious threat to Colorado’s urban forests, will be releasedtomorrow in Boulder to help control the borer’s spread. More than a thousand Tetrastichus planipennisi, which target EAB larvae specifically, will be brought into an area of known infestation by experts on the interagency Colorado EAB Response Team.*


The Colorado Department of Agriculture, University of Colorado and City of Boulder worked with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) to obtain the wasps as biocontrol measures, to help suppress EAB populations in the city and manage the insect’s potential future spread. The release will occur on the East Campus of the University of Colorado.

“Biocontrols like these won’t eradicate EAB, but they are additional tools we can utilize in our integrated management approach to help control EAB in Colorado,” said Mitch Yergert, Director, CDA Plant Industry Division and incident commander for the EAB Response Team.

The release is being conducted in cooperation with APHIS and partner agencies under specific guidelines for the use of EAB parasitoids. Female Tetrastichus wasps lay eggs inside EAB larvae hidden under the bark of ash trees, and the growing parasitoid larvae ultimately kill their EAB hosts before they can mature. The stingless wasps are not attracted to people or pets.

“The wasps are hard-wired to seek out and find EAB,” said Mary Mahaffey, APHIS Acting State Plant Health Director. “Once a wasp senses an EAB larva, it uses an organ that looks like a stinger to drill through the bark, into a larva, where it can lay more than 100 eggs in a single host. Despite their appearance, the wasps cannot sting, and that’s why they are referred to as stingless.”

USDA initiated a biological control effort shortly after EAB was detected in Michigan in 2002.  In the beetle’s native range of China, three potential biological control agents (stingless wasps) were identified – Spathius agrili, Tetrastichus planipennisi and Oobius agrili. After extensive evaluation – to determine the efficacy of the wasps at killing EAB and the possible impacts on native wood borers – they were first released in Michigan. Today the EAB Biological Control Production Facility is rearing the wasps for release, and since 2007, one or more parasitic wasp species have been released in 18 of 24 states where EAB has been confirmed.

Up to two additional Tetrastichus releases are planned in Boulder in the coming weeks, dependent on weather conditions. The parasitoid wasp Oobius agrili, which targets EAB eggs laid in the late spring or summer, also is being considered for release in Boulder in 2015.

EAB, a non-native pest responsible for the death of millions of ash trees and billions of dollars in costs in 24 states, was first confirmed in Boulder in September 2013, but to date has not been detected elsewhere in Colorado. Ash species comprise an estimated 15-20 percent of all trees in the state’s urban and community forests.

More information about USDA’s Emerald Ash Borer Biocontrol Program can be found athttp://www.aphis.usda.gov/publications/plant_health/2014/faq_eab_biocontrol.pdf.

*The Colorado EAB Response Team is comprised of members from the following agencies/organizations: Boulder County, City of Boulder, Colorado Department of Agriculture, Colorado State Forest Service, Colorado State University Extension, Colorado Tree Coalition, Green Industries of Colorado, University of Colorado and USDA Animal and Plant Health Inspection Service.

EAB: What Coloradans Need to Know

  • Learn how to identify ash trees, and signs of EAB infestation in ash trees:
    • thinning of leaves and upper branches and twigs
    • serpentine tunnels produced by larvae under the bark
    • D-shaped exit holes 1/8-inch wide
    • new sprouts on the lower trunk or lower branches
    • vertical splits in the bark
    • increased woodpecker activity
  • Don’t apply unnecessary chemical treatments, and talk to a professional forester or arborist before applying any treatment. If hiring someone to apply pesticide treatments, the applicator must be licensed by the Colorado Department of Agriculture as a Commercial Pesticide Applicator. Chemical treatments are not recommended more than 5 miles from a positive detection.
  • Never transport firewood or other products from ash trees, as this is the most likely method of accidental spread. A quarantine is now in place in Boulder County and surrounding areas to try and prevent the human-assisted spread of EAB.

For current information about EAB in Colorado, including the current quarantine in Boulder County and surrounding areas, go to www.eabcolorado.com. If you think you have EAB in your ash trees, please contact the Colorado Department of Agriculture at 888-248-5535 or emailCAPS.program@state.co.us.