Tiny Wasp to Help Battle Emerald Ash Borer Beetles

Posted on May 27, 2016

Spathius galinae

A tiny wasp species, Spathius galinae, will be introduced in an attempt to control the emberald ash borer beetle. The beetle has been devastating ash tree populations across the United States. Research conducted by the University of Delaware (UD) and the United States Department of Agriculture (USDA) Agricultural Research Service (ARS) found the parasitoid wasp could help in the beetle battle.

Timothy Watt, who received his master's degree from UD in 2014 and worked at the USDA Beneficial Insects Lab on campus, was the lead author on a research paper about the wasp. Watt says, "You've got to know the biology but then you also have to know the environmental factors and for this one, we just focused on temperature because you can start to get into all sorts of other studies and data analysis when you add other variables."

The researchers tested five different temperatures and found 25 degrees was the most optimal temperature. This temperature will minimize the wasp's immature development time and maximize female reproductive output. The researchers also spent a great deal of time making sure the parasitic wasp was host specific to the emerald ash borer and won't impact any other similar species.

The wasp is currently being reared in the USDA Animal and Plant Health Inspection Service (APHIS) lab in Michigan. The wasp locates the emerald ash borer larvae first by smelling the ash tree. The wasp then walks on the tree's trunk and uses sensors in its legs to detect the vibrations of the emerald ash borer larvae feeding. Once a wasp feels larval vibrations it uses its ovipositor (about 3-5 millimeters long) to drill through the bark and lay eggs on the surface of the larvae. Once the parasitic wasp larvae hatch, they begin to feed on and suck the juices out of the emerald ash borer larvae.

A research paper on the study can be found here in the journal, Biological Control.

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