The irridescent, green-copper beetle is easy to spot. Getting rid of them on the other hand ...
'Tis the season for garden devastation and destruction, all at the seemingly insatiable appetite of a tiny beetle.
Enemy of the eggplant, lawbreaker of the lawn, scourge of the soil, bad guy of the backyard. You get the picture. Japanese beetles have made their annual appearance in Colorado gardens and are eating their way through their life cycle. It's not hard to spot the beetle (they are actually kind of pretty) or their damage, which will leave lacey-looking holes on plant leaves—they are voracious consumers of hundreds of plant species, so basically everything is part of their buffet.
These invasive pests first came to the U.S. in the early 1900s, and they hitched a ride on nursery stock purchased from the Midwest in the early 1990s. They aren't fans of dry conditions, but the lush, watered landscapes of urban areas in the state are the perfect breeding ground for beetle mania.
If you have just a few, picking them off the plants and dumping in soapy water can keep them at bay. However, it generally isn't that easy, and here is why: female beetles of this species can lay between 40-60 eggs through their adult life cycle (which generally lasts about 2 months). In between laying eggs in the soil, they consume plants around them to gear up for another breeding cycle. The eggs develop into grubs, which weather out fall and winter conditions, so the next year's population (which will emerge from the ground in June/July) is just waiting for their time to chomp away on your produce (not to mention the damage they can do to lawns). If you want all the details on the full life cycle, Orkin.com has a really good rundown.
Lifecycle of the Japanese Beetle (Starts with laying eggs on right and through the process to hatching on left) Courtesy of Joel Floyd, USDA APHIS.
So you can see how easily a few beetles can become a whole swarm. In addition, they've all caught the travel bug, as in they can fly up to five miles to find a food source. As they feed, they both release pheremones to attract others and cause plants to release oils that also bring more beetles to the yard.
So, how can you get rid of them? There are a few techniques that address the whole lifecycle that could give your poor garden a little relief.
If you have a small infestation, pick them or shake them into a bucket of soapy water. Feel free to crush a few if it gives you a feeling particularly vengeful.
There are several practices that could help control them at all points of the life cycle. You can start by not planting species that the beetles will feed on. This can be tough, as they enjoy snacking on over 300 species of flora, including garden favorites like roses.
Because the beetles don't like drier conditions in the egg stage, if you are in a place where you can limit watering your lawn, that might work. Though it's a fine line between killing beetles and killing your whole yard. In addition, longer grass helps to discourage egg-laying, though for those in an HOA, this might not be allowed.
There are also beetle traps, biological controls, and chemical controls to help keep the mighty munchers in check.
Entomopathogenic nematodes, parasitic worms that enjoy insects, are great at controlling grubs. There are also bacteria that can cause disease in grubs, thus killing them before they can hatch. Visit a local garden center to get more information.
In terms of insecticides and pesticides, timing is everything. The Colorado Department of Agriculture (CDA) has a list of approved chemical controls for Japanese beetles on its website. Please remember that many of these controls can put pollinators at risk, so use them as instructed to reduce harm.
"Insecticide treatment of turf to control larvae (grubs) has been the most common and largely the most effective management strategy employed against Japanese beetle. The timing of insecticide applications is critical. Use insecticides for grub control in early summer, for control of adults, apply when feeding and damage are observed," says the CDA.
Perhaps the best strategy is a mix of all the above. Called Integrated Pest Management, this method uses everything it can to tackle the beetles at all stages of the life cycle.
If you are looking for more information on the beetles and control, check out the CDA website and the Colorado Extension Service website. Extension agents, if you have one in your area, are fantastic resources if you'd like to talk to someone face to face. Find the county office locations here.
Has there been a beetle invasion in your yard, garden, or neighborhood? Let us know in the comments below!