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How to Treat for the Japanese Beetle in Denver

The Japanese Beetle is relatively new to Colorado, but its impact has already been felt across the state, including in Denver.

The beetle has been a destructive pest in the United States since the early 1900s, but it didn’t show up in Colorado until the 21st century. After successful eradication practices in Palisade, the beetle came back in a big way around 2005. Since then, it has been a nuisance to plants and lawns across Colorado.

At Mountain High Tree, Lawn & Landscape we offer treatment options for the Japanese Beetle. As local lawn care and insect and yard pest control experts since 1974, we have witnessed the bug’s rise in Colorado.

Below we have answered some common questions about the Japanese beetle we at Mountain High Tree & Lawn hear a lot. We have also included Japanese Beetle control options, but keep in mind we treat each case differently. We hope you find this useful.

What Does the Japanese Beetle Look Like?

The adult Japanese Beetle is metallic green in color, with coppery wings that don’t cover its abdomen. Japanese Beetle larvae are white grubs.

What Plants are Affected by the Japanese Beetle?

The Japanese Beetle has quite the appetite. The adult beetle feeds on the leaves, buds and flowers of more than 300 trees, shrubs, fruits and vegetables. The adult particularly likes (in order): roses, the Virginia Creeper, grapevines and trees such as lindens, plum trees, oaks, birch and American Elm. Larvae, on the other hand, feed on plant and tree roots, which cause root damage, making it more difficult for roots to absorb water and nutrients to keep plants healthy.

When Does the Japanese Beetle Show Up in Colorado?

The Japanese Beetle generally shows up during the warmer months, from March to September. Larvae will feed on the roots of grasses for as long as nine months. Adults will generally appear as early as mid-June and begin feeding and populating through July and into August.

How Can I Treat for the Japanese Beetle?

Pheromone traps can be useful for monitoring the Japanese Beetle. In terms of actual treatment, there are several pesticides that can help, including Imidacloprid (adult or larvae), Acelepryn (adult or larvae), Milky Spore (larvae), Bifenthrin (adult), Parasitic Nematode (larvae) and Acephate (adult). Cutting your grasses to the recommended length of three inches can also help control larvae.

If you are interested in pest control services for the Japanese Beetle, call us at Mountain High Tree & Lawn at 303-232-0666 or visit us at We will provide an initial inspection free of charge. We feature both synthetic insecticides and natural products.