AUBURN UNIVERSITY – Within a few days of discovering a native parasitic fly that may reduce kudzu bug numbers significantly over time, Alabama Cooperative Extension System specialist and Auburn University researcher Xing Ping Hu has discovered a local egg-parasitic wasp.
The finding – the first discovery of a local wasp that parasitizes eggs of the exotic kudzu bug – could prove to be a game changer in the fight against this invasive species, Hu said. Along with the earlier finding of a fly that preys on kudzu bug adults, Hu said the discovery of the parasitic egg wasp doubles the frontline of defense using natural enemies to fight this pest.
“This local parasitoid wasp has demonstrated a high capacity to reduce significantly the populations of kudzu bugs in soybean fields,” she said.
The discovery was made by Hu’s research assistant, Auburn University graduate student Julian Golec, during a routine field investigation of kudzu bug damage in a soybean field. Golec noticed black masses within kudzu bug eggs – something that immediately caught his attention because the translucent eggs normally are characterized by a pinkish or yellowish tint. Even more intriguing, the black masses appeared to be moving. He suspected that he had discovered evidence of a local predatory wasp that finds kudzu bugs suitable repositories for its own eggs – a hunch confirmed through follow-up investigation.
“Using a high-speed camera, the wasps were recorded and observed under a microscope as they emerged from these parasitized kudzu bug eggs,” Hu said. “The male wasps emerged first, guarding the parasitized eggs until the females came out.”
The female wasps emerge sexually mature. As soon as the wasps emerge from the eggs, they mate and the females immediately begin laying eggs, repeating the cycle. The rates of parasitized eggs turned out to be especially high.
Hu said kudzu bugs are no different than any other insect species introduced into a new area. Figuratively speaking, entering an area with no known indigenous predators is like drawing a lucky lotto number: The species thrives and its numbers mushroom as it develops into a full-blown invasive species, often wreaking havoc within its new environment.
“That’s why they become invasive in the first place,” Hu said. “They have no natural enemies to balance the ecosystem. It’s as if they’re saying, ‘No one can mess with me so I can do what I want.’”
On the other hand, an incoming species is unlucky if it enters an environment teeming with natural enemies. In such cases, the species’ numbers may spike for a few years until local predators respond to the new species.
In the case of some invasive species, such as the red imported fire ant, the U.S. Department of Agriculture has stepped in to identify predators from the invasive species’ native habitat that could be introduced to reduce their numbers.
“This typically is a long, labor-intensive and expensive process that requires laboratory studies to ensure that this predator is not only capable of surviving in its new environment but also that it preys only on the targeted invasive species and doesn’t attack native species,” Hu said. “Even if the species overcomes these laboratory hurdles and is introduced, it’s often an open question whether it can survive in sufficient numbers to make a difference.”
That is why Hu is excited about the discovery of the local predatory wasp species. Its discovery, along with that of the fly species, may help provide less expensive methods for reducing kudzu bug numbers.
Aside from confirming that there is yet another local predator of kudzu bugs, Hu said the wasps exhibit higher levels of parasitism than the recently discovered flies. Egg parasites typically are more effective predators than species that prey only on adults, she said.
In fact, preliminary field investigations reveal that more kudzu eggs than not appear to be parasitized by the wasps – evidence that the kudzu bug populations that emerge in the future may not be as large as they have in the past.
(Submitted by Jim Langcuster.)
Contacts: Jim Langcuster, Alabama Cooperative Extension System, (334) 844-5686 (firstname.lastname@example.org, or Charles Martin, Auburn University Office of Communications and Marketing (334) 844-9999 (email@example.com)