Tofu Has a Mortal Enemy—And It’s Only a Quarter Inch Long

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The kudzu bug has arrived from Asia, and it's spreading rapidly throughout the southeastern United States. Considering that the bug usually eats kudzu, an invasive plant that has displaced many native species and wreaked environmental havoc, one might be tempted to think that this isn't such a bad thing.

But there's just one problem: The kudzu bug is also rather fond of eating soybeans, and new research shows it can complete an entire life cycle on soybean plants, devastating whole fields of the legume. It also has no known natural predators in the United States.

Given the bugs' ravenous appetite and ever-expanding range, the insect is poised to create real trouble for soybean farmers nationwide, and perhaps even in other countries, said Dominic Reisig, a researcher at North Carolina State University.

 

 

The bug, native to Japan and East Asia, was first found in the United States in 2009 in Atlanta, Georgia, Reisig said. By 2010, it was only found in one county in North Carolina, two states to the north. By 2011, it was found in half of the state's counties. Last year, it was found in every county sampled.

It can now be found as far west as Mississippi and Tennessee and north to Virginia. From 2011 to 2012, the estimated cost of treating the insect in North Carolina alone increased more than tenfold, to $840,000, Reisig said. It's likely to cost more than ten times that much to treat it this year, he said.

The kudzu bug has a unique lifestyle. The first generation hatches in the spring. Then these bugs lay eggs and give rise to a second generation in the summer. These second-generation insects mature in a couple months and lay eggs that hatch in the spring.

The kudzu bug was previously thought to have just chomped away at the kudzu plant. Then some first-generation adults were found transferring to soybeans and laying eggs that grew up eating the crop. And Reisig's research has found that these pernicious bugs can survive on soybeans during all phases of their lives. His latest study was published recently in Journal of Economic Entomology.

One experiment in Georgia illustrates the impact of the bugs. The experiment looked at two fields, both infested with kudzu bugs; one field was sprayed with insecticide, while the other was left alone. The untreated field lost 70 percent of its yield compared to the treated one, Reisig said. He estimates that infestations may reduce soybeans yields by about 15 percent on average.

The good news is that the bugs are relatively easy to treat, with one application of common insecticides. But this isn't ideal, since you never want to have to spray more pesticides, Reisig said. There is currently work being done to see if a parasitic wasp—which lays eggs inside the bug's body—can be imported from Japan. But the research is still underway, and getting the necessary approval to introduce an exotic species can take years.

Meanwhile, the bug is spreading quickly, thanks to its strong flying ability. Reisig said the bugs could possibly live just about anywhere that soybeans grow, though it doesn't tolerate cold weather early in the season very well.

The insect is also a capable hitchhiker. The insects are found on tall, white objects—Reisig, as an extension specialist, often gets calls from homeowners annoyed to find a huge group of the bugs on the exterior of their white houses. Considering the bug was first found near an airfield in Atlanta, Reisig guesses that the bugs may have hitched a ride on an airplane. They are likely spreading via automobiles as well. One recent discovery of the bugs, in Mississippi, took place a long distance from the nearest known infestation.

"It looked like it jumped the whole state," Reisig said. "That was on a kudzu patch by the interstate."

The area's soybean farmers better be on the lookout.

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Douglas Main is a science and environmental journalist. He's currently a staff writer for LiveScience.com and has written for such venues as the New York Times Green Blog, Popular Mechanics and Discover Magazine. He has an M.A. in journalism from New York University and lives in New York City.  TakePart.com

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