Invasive Japanese beetles are back in Denver and Colorado — and they are hungry
Yup, it’s official, Japanese beetles (Popillia japonica) have returned to infest Colorado gardens — albeit perhaps a bit later than usual, some gardeners have noticed.
The shiny, round, invasive pests typically show up in June and stick around all summer — what’s worse, the most reliable method for getting rid of them is waking up at the crack of dawn and plucking them off your plants one by one (ew) and then drowning them in a bucket of water.
Central Denver resident Carol LaRoque gets rid of her bugs in a slightly different way — by feeding them to her neighbor’s chickens, who quickly gobble them up (the animals are noted in numerous sources as an excellent and efficient natural beetle repellent). She said she’s plucked only about a dozen beetles off her roses so far, but is certain this is just the beginning.
“It does seem like they emerged later this year,” she noted. “I didn’t write down the date last year, but it seemed like by some time in late June, we had already had them last year.”
Colorado gardeners have been quick to raise the alarm about the return of the leaf- and flower-hungry fiends. Colorado State University’s Master Gardeners have been posting about them on social media since June 29, with a few helpful fact sheets about controlling them and keeping them out (The Denver Post has its own guide here), but they have so far been fewer in number.
The late beginning to beetle season in some areas may be due to the dry winter Colorado experienced, according to Richard Levy, a scientific data manager at the Denver Botanic Gardens, where Japanese beetles are just now beginning to show up.
Japanese beetles lay their eggs in turf grass, where they spend 10 months in the larval stage underground. Frozen, barren soil uninsulated by snow for long periods of time can lead to later adult beetle emergence from the ground, and that may be what some areas are seeing now.
Although they appear to be leaving the rose bushes alone in favor of the hollyhocks (for now), Denver Botanic Gardens communications director Erin Bird recalls garden volunteers having to scoop off hoards of beetles by this time in years past.
Oh — and hand plucking and natural remedies really are best — spraying pesticides will end up doing more harm to your yard and garden than the beetles will. Some gardeners have turned to replacing their lawns with native plants to avoid providing the perfect place for new eggs to hatch.
Japanese beetles have been active in the Denver metro, Boulder, and Pueblo for over six years now. As adults, they feed on the flower blossoms and leaves of over 300 different types of plant species. Their larvae chow down on plant roots — particularly the roots of Kentucky bluegrass. And while their appearance may have been delayed, beware — they’re likely on the move to a rose bush near you.
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