Not swarms of locusts — they’re Mormon crickets. Why experts fear their rise in Idaho
Tanushri Sundar, Idaho Statesman
A cool, moist spring delayed some hatching, and population levels peaked about three to four weeks later than normally expected, Kahla Montrose, agriculture program specialist at the Idaho State Department of Agriculture, told the Idaho Statesman.
The critters should start to die off in the next month or so, Montrose said.
Mormon cricket populations surge roughly every 15 to 20 years before succumbing to predators and cold weather, Patrick Lorch, senior research biologist at the Southern Sierra Research Station in California, told the Statesman.
Their numbers have been steadily increasing in the past few years.
“I think we’re just seeing the beginning of a new outbreak,” Lorch said.
MORMON CRICKETS OFTEN A NUISANCE
Neither Mormon nor cricket, the Mormon cricket is a flightless shield-backed katydid, a close relative to the cricket. The insect earned its name after ravaging Latter-day Saints settlers’ crops in 1848.
Fond of sagebrush, the insects are most dense in Idaho’s Owyhee County and Elmore County each year, Montrose said. The species is native to the Western U.S., including Idaho.
Roughly 2 to 3 inches long, the insects have a hard, dark-colored shell. Females have a sword-like tail called an ovipositor, which they use to deposit their eggs into the soil.
“They’re not very attractive,” Montrose said.
Attractiveness aside, the Mormon crickets are still quite a spectacle when they band together in the thousands.
“It looks like the ground is moving underneath your feet,” Montrose said.
Mormon crickets can devastate crop fields, reduce feed for livestock and grazing wildlife, and damage rangeland and cropland ecosystems, Montrose said. They also infest people’s houses and buildings.
On Idaho’s hills, the insects pose another danger. Masses of slick Mormon cricket bodies can simulate icy conditions on sloped roads, Lorch said, requiring transportation officials to plow dead insects off the roads.
Our maintenance crews see a little of everything in Southwest Idaho…🦗🦗
This video is from State Highway 51 last week. Mormon crickets are taking over the road this season! Watch out for slick spots. (If you get queasy easily, don't watch this with the volume on🤢) pic.twitter.com/DzeItd0oYr
— ITD (@IdahoITD) July 21, 2022
“Our cars and trucks would be coated with dead cricket guts by the end of the season because we’re having to drive through them all the time,” Lorch said.
But the insects are an important part of the ecosystem. In addition to being food for birds and fishing bait, Mormon crickets break down plant material and release important nutrients, such as carbon and nitrogen, back into the ground.
RUNNING FROM CANNIBALS — A MARCH TO SURVIVE
The exact cause of Mormon cricket outbreaks is hard to pinpoint, Lorch said.
But one reason Mormon crickets march in dense groups, called migratory bands, is to protect themselves from predators, Lorch said.
Animals want to be in the center of a big group to avoid being eaten by a predator, a behavior biologists dub “selfish herd,” Lorch said.
In the case of Mormon crickets, a hungry predator that encounters a band might eat a few poor critters on the edge, feel full, and then leave the rest alone.
But there’s an equally ominous threat within the horde itself — cannibalism.
Any food around a dense group of crickets will be gone quickly, Lorch said. And behind every cricket is another hungry cricket with giant mandibles, ready to take a meal.
So Mormon crickets march to survive. They are not migrating as much as they are moving to new food sources and away from each other, Lorch said.
“We don’t know what exactly initiates the marching, but what keeps the marching going is cannibalism,” Robert Srygley, research ecologist in the USDA’s agricultural research service, told the Statesman.
And for insects marching miles on end, other fat and protein-rich crickets are a tantalizing snack.
“They are a high energy meal because they have a big, fat body,” Srygley said. “I don’t know how the crickets figured that out.”
PESTICIDE USE PROMPTS LAWSUIT
With farmers’ profits already impacted by hot and dry temperatures, Mormon cricket infestations bring another challenge.
The state’s Grasshopper and Mormon Cricket Control Program monitors the insect populations. When it determines an economic impact from these pests, Idaho’s State Department of Agriculture performs insecticide treatments, Montrose said. State agriculture officials primarily work with private landowners.
But the use of pesticides has remained controversial. In May, the Xerces Society and Center for Biological Diversity sued the United States Department of Agriculture’s Animal and Plant Health Inspection Service over pesticides used on federal lands to control grasshopper and Mormon crickets in Western states, including Idaho.
Thousands of bee species, pollinators, butterflies, and beetles in the sprayed areas could be impacted by insecticides, said Aimee Code, pesticide program director for the Xerces Society and Center for Biological Diversity. Birds, such as the sage grouse, feed on these insects.
The USDA’s Animal and Plant Health Inspection Service does not comment on pending litigation, a spokesperson said.
GENOME-BASED SOLUTION FOR MORMON CRICKETS?
Gregory Sword, a Texas A&M University entomology professor, is in the early stages of developing genome-based methods to only kill Mormon crickets. These methods would be an alternative to insecticides that impact several species.
A process called RNA interference can silence the expression of certain gene sequences that only Mormon crickets have, Sword said. Scientists could potentially develop a spray or a bait that targets the insects’ gene expression.
While genetic pesticides are not a new concept, they haven’t achieved much success yet, Sword said.
“Everyone’s still trying to see if we can get it to work,” he told the Statesman.
In the meantime, at least this year and next, expect these swarms of unattractive, cannibalistic pests to linger.