NEW ORLEANS (AP) — Tawny crazy ants are pushing fire ants out of some Louisiana sugar cane fields — one of the few places people are happy to see fire ants. Entomologists worry that the new invaders could hurt the crop.
"Louisiana sugarcane farmers are some of the only folks in the southern U.S. that welcome fire ants into their property, because they do a great job controlling our No. 1 pest, the sugarcane borer," said Blake Wilson, an LSU AgCenter agronomist. "It helps them use less insecticide and save money."
Sugarcane borers are moth larvae that tunnel into sugarcane stalks, eating sugar and blocking the upward flow of nutrients.
Fire ants have been around more than 50 years. Tawny crazy ants, a Brazilian species first found in Texas in 2002, began moving into some Louisiana sugar cane fields a couple of years ago, Wilson said.
They're flea-sized and their bite is much less painful than a fire ant's sting, but they make up in numbers what they lack in strength, showing up in the millions, scrambling randomly as they forage. They've made a major name for themselves as urban pests, short-circuiting electrical equipment and clogging switches. When pesticide's applied, heaps of dead ants shield others which scramble over their bodies.
"When dead ants build up in piles, the piles must be removed to treat the area under the dead ant piles," the LSU AgCenter notes on its website. Use a leaf-blower so remaining pesticide isn't disturbed, it advises.
In sugar cane fields, tawny crazy ants do eat sugarcane borers. But a big worry is that they also are known to protect aphids and other sap-sucking insects that exude a sweet substance called honeydew, which ants eat, Wilson said.
Florida is the nation's top cane sugar producer. A survey of ants in Florida's sugar cane fields in 2017 and 2018 didn't turn up any tawny crazy ants, said Julien Beuzelin, an assistant professor of insect ecology and pest management at the University of Florida Institute of Food and Agricultural Sciences.
Beuzelin said he had read that either the ant or a closely related species has been reported in coastal Palm Beach County, which accounts for 70 percent of Florida's sugar acreage. "I don't know the biology of the insect really well, but I don't know why it wouldn't get" to the cane fields, he said.
A University of Florida study published in 2013 looked at sap-sucking insects, also called hemipterans, on 15 other kinds of plants. It found that plants with more crazy ants also had more sap-suckers. Those on southern red cedar and magnolia trees "were covered with carton shelters" that the ants likely had created to protect them, the researchers wrote.
Dr. Bill Ree of Texas A&M University has found the ants protecting aphids on pecan trees, said Dr. Robert T. Puckett, the school's extension entomologist.
"These ants are a species that spends a lot of time feeding on the sugary honeydew," Puckett said. He said people in row-crop agriculture are worried, but he doesn't know if anyone has much information about how much or little harm they may do in crops.
Wilson is planning studies to look at the crazy ants' effectiveness at keeping down sugarcane borer infestations, and others to look at their interactions with other insects.
"We're also trying to get a better understanding of where they're present and how quickly they're expanding into new areas," he said.
The ants have been found in at least 26 of Louisiana's 64 parishes, including 16 of the 24 where sugar cane is grown. Wilson said they've been found in cane fields in Lafourche, Terrebonne, St. Charles, St. James, Assumption, St. Martin and Iberia parishes.
"Even within those parishes distribution can be pretty spotty," Wilson said. "I've seen some areas where they're in one field, and you go across the highway and they're not in those fields yet."
Tawny crazy ants have been on the move for nearly two decades since a Texas pest control operator identified them in 2002 as a new invader — or, as an IFAS Extension Service coloring book puts it, ant-vader .
"For a few years they just kind of smoldered away in Houston. We've got them now in 39 counties. That's just confirmed populations," Puckett said. "They're in Mississippi, Alabama, Florida, up into Georgia."
And since they're in one Georgia county that borders South Carolina, he said, "It's pretty clear they're going to be into South Carolina soon."