The bacteria are making a bad problem even worse. The type of sweet potato whitefly they infect, called B biotype, was already a major problem for farmers, on every continent where crops are grown.
Don't let the name fool you - the B biotype whitefly doesn't just dine on sweet potatoes. And that's just the problem. It eats more than 600 types of plant, so it never goes hungry.
"Here in Arizona, it probably starts out on weeds in the spring, and then moves on to melons, and when melons are done, it moves in big numbers onto cotton and feeds on that all summer long," Hunter said. "In the fall, it moves on to vegetables, and so it just keeps going."
"In the late 1980s and early 1990s, when this new biotype arrived in the Southwest, the population just exploded," Hunter said. "Sometimes you could see clouds of whiteflies in the air, gumming up windshields."
"With integrated pest management practices, many developed by colleagues here at the UA, their impact has decreased tremendously, but they still are the worst pest in Arizona's cotton industry. If it wasn't for whiteflies, farmers would be spraying cotton a lot less," Hunter said.
Now the tiny insects, which measure less than 1/16 of an inch, have been super-powered by the Rickettsia bacteria and pose an even bigger threat. But all hope is not lost; Hunter wonders if there might be a way to turn the tables.
"It would be interesting to see if by having a microbe that has this big effect in one direction, if you could make it so that it has an effect in the other direction, to help control the pest," Hunter said. "Could we use symbionts in a way to make things less of a problem, to manage pest populations in a more sustainable way?"
Knocking down whiteflies would be a huge help for farmers. The insects, not true flies, but actually members of the order Hemiptera, are more closely related to true bugs and aphids, another pest. And like their aphid cousins, they leave behind a sticky residue that can become home for fungi, which further damage plants' leaves. Plus, they transmit more than 100 viruses, such as the mosaic virus.
IMAGE 1: The sweet potato whitefly, (Bemisia tabaci) (Wikimedia Commons).
IMAGE 2: The sweet potato whitefly, (Bemisia tabaci) (Wikimedia Commons).
IMAGE 3: Mosaic virus on cabbage (Wikimedia Commons).