From Russia; A Wasp To Save Americas Ash Trees.

The biological control of pest species is becoming a ecologically friendly, cheap, and sustainable way to help invasive species, if done right.

So with this in mind many scientists are now scouring the globe looking for bio-controls that will help to maintain invasive species being introduced. Dr  Jian J. Duan, took this search to Russia, in the Primorsky Krai region. This region is known for its undisturbed hardwood and conifer forests, known to be the last stronghold of the Siberian tiger. What Duan was looking for in these forests was much harder to find then evident tracks of tigers, although they did not see any.

looking under loose bark of natural crevices found in the trees of the ancient forests. Going from tree to tree, they finally found them.


These eggs belonged to the well known Emerald Ash Borer beetle (EAB), well known & hated within both the UK & USA. Originating in northeastern China, Japan, the Koreas and the Russian Far East, this beetle has killed tens of millions of ash trees in the United States of America alone after is detection in 2002.


The eggs that Duan has spent time looking for were off these beetles, but they were looking for a particular type of egg from these beetles, black eggs, More importantly Parasitized eggs.

These eggs had turned black, meaning that they had been visited by a particular wasp. This wasp turned out the be a previously unknown species of EAB parasite, the team later found that it was taxonomically seperate from a known look-alike after much painstaking research in USDA labs back in Delaware.

These two parasitoids are tiny little sting-less wasps that are of the genus Oobuis, they are so morphologically similar to others that they need to be identified by segments of the antennae & ratio of the length to width. The distinguishing of these species is an extremely hard task and not 100% full proof given the animal is the size of a gnat. But genes never lie, by comparing genomes of the animals they showed that they were distinct at a molecular level, as well as showing distinct behavioural differences.

The new species was named O .primorskyensis, after the area were it is found.

The other species that the O. primorskyensis is so closely related to is the O. agrili. O. agrili along with O. primorskyensis are both parthenogentic, a type of asexual reproduction in which the offspring develops from unfertilized eggs. The use of O. argrili has been used since 2007 in the U.S.A to control EAB.

The use of these animals as biological controls is based on their paritisation of the EAB eggs, which proved food for the wasps larvae. With both wasps being used and their specific behavioural changes during winter, with O. agrili preferring becoming dormant to over winter, allows for a constant year long attack on the invasive animal. With the two wasps ecological differences Dr. Duan has sugested that O. primorskyensis could be a more powerful weapon in the fight against EAB, especially in cooler climates. Behavioural observations of the species has shown that its behaviour & life cycle follow the EAB closer then the O. argrili.  In a nutshell, almost a full generation of O. primorskyensis larvae overwinters and then emerges as adults in July, ready to parasitize the EAB when it is laying the bulk of its eggs, a period of only 10 to 120 days at most. These finding back up the hypothesis that under cooler conditions, O. primorskyensis could destroy a significantly large proportion of the seasons’s EBA’s offspring. In comparison O. agrili can produce two or three summer generations, but only a fragment diapause for overwintering, so they may be found to be more effective if deployed in warmer southern area, were the EAB eggs are laid for a longer period.


Hopefully pest control managers will be able to tailor the use of each wasp to its most efficient geographical climate to prevent or remove the threat of EAB. O. primorskyensis is currently still in quarantine, and is being evaluated for its possible deployment in the field in the soon future. If approved, this species can be a real aid in halting the spread of EAB and managing outbreaks, complementing the work the O. agrili has already done in the fight against this invasive species. By understanding the changes that a few details in genetics can have on an animals behaiviour, despite being nearly identically morphologically, has proven it could have a practical payoff of immense importance in the effort to save the ash trees of the U.S.


Please be aware that the photos in this post are of the EAB, unfortunately there are no photos of the O. primorskyensis available to the public yet.

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A Behavioral entomologist. I love the little things that are often overlooked.

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3 Responses

  1. Avatar Quinn says:

    Do you have supporting documentation for your statement, “The use of O. argrili has been used since 2007 in the U.S.A to control EAB”? Because I am in the US and have been seeing warnings and alerts about EAB for years, but this is the first I’ve heard that we are controlling EAB with imported wasps. Thanks.

  2. Avatar Quinn says:

    My question from 2 weeks ago is still “awaiting moderation”?

  3. Avatar Quinn says:

    Okay, I give up on ever getting a response and won;t check back again.
    I do wonder why you even bother having a “Comments” section!

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