The winter may seem quiet, but 12 inches below the ground, Japanese beetles are already dining.
The grubs are chewing on grass, killing lawns while they protect themselves.
By late June, the beetles are fully grown and ready to eat their way across the Missouri landscape.
For at least a month, they will devour fruit trees and flowers, leaving only the skeletal remains.
These metallic green-and-copper beetles could easily be among the most destructive pests in the country. They feed on more than 300 species of plants, including roses, sassafras, apples, peaches and grapes.
In 2016, Les Bourgeois Vineyards, one of Missouri’s largest wine producers, suffered $20,000 in losses during a particularly grim beetle season.
Soybeans and corn, among Missouri’s top agricultural commodities, are also big targets. The beetles will eat soybean foliage and corn silks, extensively damaging the crops.
But two MU researchers are in the process of devising a method to combat the bugs and reduce crop damage.
Kevin Rice, assistant professor of plant science, and graduate student Kelsey Benthall are developing a net system that can lure and trap Japanese beetles. Once ensnared, the beetles will be exposed to an insecticide that will kill them.
The pesticide is “impregnated” within the fibers of the netting. As a result, the pesticide won’t wash away in the rain. It will take just three seconds of contact for the beetles to receive a fatal dose and die.
The netting looks like the material used to prevent mosquitoes from infecting humans with malaria. It works by using pheromones known to attract the beetles.
Pheromones are also used in the widely available traps for sale in stores and online, but Rice doesn’t recommend them. They actually draw more Japanese beetles than they kill, he said.
“They spill over,” said Rice. “It’s an aggregation pheromone.”
The aggregation pheromone lures male beetles. Because it’s not a sex pheromone, it simply gives the signal “there’s good food here” to the bugs.
Aggregation pheromones are also used in the net system, but it’s designed to attract female beetles as well as males using a floral volatile. Both will be lured into the nets and poisoned.
Because the pheromones are specific to beetles, the system is not expected to attract other insects, such as butterflies and bees.
Rice and Benthall are also looking at what’s called “plume reach,” or the trap distance of the pheromones.
In their tests, Japanese beetles are marked with spray paint and placed different distances from the net. Plume reach determines how far the pheromones will reach and still pull in the beetles. This will help decide placement of lures and nets.
“We’re also assessing if it draws more beetles than without those pheromones,” Benthall said.
The upcoming year will be important for further research of the net system. Last summer, population numbers for beetles were lower than usual because of a persistent drought. Numbers are likely to be higher next year, the researchers believe.
“We expect high populations, so that will be a real interesting part of it,” Rice said. “It might not work as well on high populations, which we will need to assess.”
Though still early in the research process, the net system has shown promising results, Rice said.
“It’s preliminary data, with a low population,” he said. “But [Benthall] saw it was roughly equivalent protection as weekly sprays to plants.”
Even if the net system only works at the beginning and end of the beetle cycle, before the beetle population is at its peak, that could help farmers limit their use of chemical sprays.
Benthall and Rice will be collaborating with Dr. Theo Skevas, an MU professor in the Division of Applied Social Sciences, on an economic analysis. It will look at affordability of the project and see “if it’s worth it.”
Pesticides, so far, have been Bruce Arnett’s answer to the Japanese beetle problem. Arnett, the owner of The Peach Tree Farm, has used Sevin pesticide when matters got out of hand.
He said he first saw the beetles 15 to 17 years ago. From there, Arnett said the numbers grew until peaking in 2018.
“2018 was the worst year I ever saw,” Arnett said. “I mean, I have never seen an infestation like we had. So I sprayed, and, when I spray, I bet I kill millions.”
Arnett waited until the infestation was bad, then hit the beetles once with a 300-gallon sprayer.
So many beetles died, Arnett continued, that thousands of their carcasses covered the grass underneath the cypress toward the entrance of the farm.
Soon, there was a stench of decay. At first he thought an animal had died under the porch. He finally realized it was dead beetles.
“This is not a hobby farm,” Arnett said. “If you want to keep it, you spray it. I wish it were not so.”