With the emerald ash borer beetle devastating ash tree populations throughout the United States, solutions to help fight the insect are critical. Thanks in part to research from the University of Delaware and the USDA’s Agricultural Research Service, a host-specific parasitoid wasp from Russia — Spathius galinae — has been approved for release to help control the invasive beetle. Some of the research findings were recently released in the May edition of the journal Biological Control.
Timothy Watt, the lead author on the paper, said that the researchers looked at the effects of temperature on the parasitoid’s development in reproductive biology.
“Insects in general are ectothermic — they’re basically controlled by temperature,” he said. “Their physiology and metabolism are strongly influenced by ambient temperature, almost like they’re programmed in a way.”
The researchers also spent a great deal of time making sure that the parasitic wasp was host specific to emerald ash borer and wouldn’t impact any other similar species.
“There’s a lot of behavior and ecological mechanisms to prevent this wasp from attacking other insects,” said co-author Jian Duan. “Prior to the regulatory approval, we conducted extensive host specificity testing against 14 different non-target beetle species in the quarantine laboratory. Only one of the 14 non-target beetles was impacted, and that was the gold spotted oak borer, which itself is a serious invasive pest of oak trees in California. But that’s under laboratory conditions. In general, this is one of the most host specific wasp species of emerald ash borer natural enemies.”
According to Watt, it can take up to four or five years of research conducting non-target testing before a biological control measure is even considered for release.
“A lot of our work focuses on non-target testing, looking to see if the parasitoid might seek out other insects that live in the same habitats or are taxonomically related to the target pest,” he said. “There is a very rigorous testing model in place to make sure that these organisms aren’t all of a sudden going to go attack another insect that’s out there once we release them into the wild.”
But wait, it gets better. These wasps do not sting.
“These wasps do not sting human beings,” said Duan. “They don’t even sting ‘naked’ emerald ash borer larvae dissected out of the bark. They simply lay eggs on it.”
“People worry because it’s a wasp,” said co-author Douglas Tallamy. “They wonder ‘will it sting my kids?’ They’re picturing bigger wasps. These are tiny. Nobody would look at them and recognize them as a wasp. They’d think it’s a little gnat or something. They will never sting you. They couldn’t sting you.”
Now that the studies have been completed, the Spathius galinae has been approved for release and is currently being reared in the USDA Animal and Plant Health Inspection Service lab in Michigan.
“Because we have done all these studies, we have developed an effective rearing program and USDA-APHIS approved it for release in the United States as of May 2015,” said Duan. “The parasitoid colony has been transferred to a USDA-APHIS lab in Brighton, Michigan, where APHIS has a mass rearing facility for all emerald ash borer parasitoids, including this one. The plan is, they’re going to produce tens of thousands of these parasitoids and send them to northeastern states to release.”
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