Within only a few days after 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.
This finding — the first discovery of an indigent wasp that parasitizes eggs of the exotic kudzu bug — could prove to be a game changer in the fight against this invasive species, Hu says.
Along with the earlier finding of a fly that preys on kudzu bug adults, Hu says the discovery of this parasitic egg wasp doubles the frontline of defense using natural enemies to fight this exotic pest.
“This local parasitoid wasp has demonstrated a high capacity to reduce significantly the populations of kudzu bugs in soybean fields,” she says.
The discovery was made by Hu’s research assistant, Auburn University graduate student Julian Golec, during a routine investigation of kudzu bug damage in a soybean field.
Hu says kudzu bugs are no different than any other insect species introduced into a new area. Figuratively speaking, entering an area with no known local 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 says. “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 draws an unlucky lotto number 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.
Often an expensive process
“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 says.
“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 the reason why Hu is excited about the discovery of the local predatory wasp species. The discovery of this species, along with the fly species may ultimately prove to be less expensive methods for reducing kudzu bug numbers.
During his field investigation, Golec noticed black masses within kudzu bug eggs — something that immediately caught his attention because these translucent eggs are normally characterized by a pinkish or yellowish tint. Even more intriguing: These 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 subsequently confirmed through follow-up investigation.
“Using a high-speed camera, the wasps were recorded and observed under microscope as they emerged from these parasitized kudzu bug eggs,” Hu says. “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 parasitic rates of parasitized eggs turned out to be especially high.
Aside from confirming that there is yet another local predator of kudzu bugs, Hu says these 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 says.
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.
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