Predatory wasps take aim at beetle mania

Colorado researchers receive help to fight spread of Japanese beetles

The most action-packed summer blockbuster in Colorado isn’t playing out on the silver screen, but around a rosebud’s roots: predatory wasp versus invasive Japanese beetle.

The unwelcome beetle — a six-legged, flying insect no bigger than a fingernail — haunts gardeners’ psyches with its ability to make healthy leaves look like Swiss cheese. Its chilling presence on plants across Colorado’s Front Range has been felt, and seen, particularly hard this year, prompting drastic measures from local horticulturists and entomologists who just want the beetle to croak.

With that in mind, shipments of live predatory wasps were mailed this year from North Carolina to Colorado researchers, who released them into the wild with an assassin’s mission: sniff out Japanese beetle larvae known as white grubs, burrow underground and lay eggs on the grubs that will eventually hatch, eating the infant beetles.

“Yes, it’s that crazy,” said Larry Hurd, supervisor of the horticulture department for Japanese beetles devour roses and leaves at the War Memorial Rose Garden in Littleton on Tuesday. Experts are now focused on longterm beetle mitigation that includes releasing predatory wasps that kill the plant-eating beetles’ larvae in the Denver area and across the Front Range.

Centennialbased South Suburban Parks and Recreation.

The beetle mitigation technique, used in Littleton’s Sterne Park in May among other locations around the Denver metro area and across the Front Range, is one of several longterm strategies local beetle virtuosos and horticulturists are testing to deal with the infestation of the planteating pests.

“Japanese beetles got to Colorado, but none of the things that attacked Japanese beetles elsewhere got here at the same time,” said Whitney Cranshaw, a professor of entomology at Colorado State University. “If this works, maybe instead of 100 Japanese beetles on your roses 10 years from now, you’ll have 20. It’s not going to make it go away, but there’s nothing right now to keep the numbers from getting bigger and bigger.”

In all of Cranshaw’s 35 years at CSU, no insect has bugged him as much as the Japanese beetle.

Part of the complication stems from the doublewhammy attack from the insect’s young and mature stages. The beetle’s grub stage damages lawns, while the adult beetle feeds on flowers and leaves that also provide food for pollinators such as honey bees, making typical insecticides out of the question for fear of killing off friendly flyers.

Years ago, Japanese beetle traps might catch 100 beetles a day, but now trappers are seeing numbers as high as 5,000, Cranshaw said.

“They just move in and …,” Cranshaw said, ending the sentence with an audible shudder.

The beetles, native to Japan and first detected in the eastern United States in 1916, likely were introduced to Colorado hundreds of times through plants grown in nurseries. But until the early 2000s, the beetles always died out.

The infestation that stuck and spread originated in Arapahoe County’s Cherry Hills Village area.

“The Cherry Hills Country Club is historically where we became aware of them in the Denver/Englewood area,” said Laura Pottorff, who manages the Colorado Department of Agriculture’s quarantine program for Japanese beetles. “There are a lot of rumors about where it got its start. It may have been the golf course that brought in trees with the beetle. It may have been a nursery down the street.

“It doesn’t matter who brought the nursery stock in. It’s here.”

Colorado is the first Western state the beetles have called home. Pottorff is doing her best to evict them.

The state’s Japanese beetle quarantine, adopted in 2010, is paid for by the nursery industry that brings its agricultural stock into Colorado.The state agriculture department charges $34 an hour to inspect nursery stock and check that the paperwork ensuring the plants are beetlefree is properly certified.

The department is also big on preventing beetlefree parts of the state, including the Western Slope and eastern Colorado, from becoming inhabited by the invasive insect.

Take a drive down Interstate 25 from Greeley to Pueblo for an idea of where the beetles have spread so far. The winged beasts are capable of flying just 5 to 10 miles in the course of their lives.

But they’re also avid hitchhikers, comfortable hopping aboard a Subaru for a road trip that can end in the beetles’ unwelcome introduction to new Colora do land.

Hurd, who has been battling the beetles for 10 years, is known to head out into the south suburban parks he supervises in the middle of the night to spray trees with cold water, watch the beetles fall to the turf below and then spray the ground with insecticide — avoiding spraying the flowering trees.

One week this year, volunteers and parks staff picked off 30,000 beetles from Littleton’s War Memorial Rose Garden, which Hurd said is one of the worsthit locations in his purview.

“That tells you what kind of problem they really were this year,” Hurd said.

Because the state didn’t get the freezes it typically gets, Hurd said, the beetles emerged weeks before they were expected and “wreaked a lot of havoc.”

When treating beetle problems at home, Hurd recommends hiring a licensed pesticide practitioner. If that’s out of the question, Hurd said homeowners can go out in the evening or early morning to pick the beetles off impacted plants and drop them into a bucket of soapy water.

For bigpicture mitigation, researchers like Cranshaw have their fingers crossed for success with biological beetle warfare such as the killer wasps or a fungus that causes chronic beetle disease.

“We can’t eradicate the pest here on the Front Range,” said Pottorff, queen of the quarantine. “We have too many people and too many landscapes. But we can make it not so nice for them.”