Barbecues, fireworks, family gatherings....and Japanese beetles. Huh? 

Over the 4th of July weekend, we had the opportunity to meet the parents of my brother's girlfriend and were invited out to their beautiful home in a golf course community near Galena. (Bear with me, there is a science lesson in here I promise). Upon arrival, I joined everyone in their large grassy backyard that happens to border the 18th fairway. I noticed a raised bed vegetable garden, so of course went to check it out. Upon closer inspection, it became abundantly clear that a Japanese beetle infestation was in full force. My brother went inside and reappeared with a mason jar of soapy water, and we went to work picking beetles off the vegetables and drowning them. The mother of my brother's girlfriend nervously laughed and stood nearby staring at us. I guess it was kind of weird to start doing this five minutes after arriving and first meeting them. To her credit, she thanked us for doing it, and then voiced the same thought I'd had so many times....what do I do to control them?

What's going on here? Why so many Japanese beetles?

Let's start at the beginning. Japanese beetles ( Popillia japonica ) are a beetle native to Japan that was first introduced into the U.S. in 1916 when Henry A. Dreer, a nurseryman from Riverton, New Jersey, imported an order of Asian iris. Unbeknownst to him, larvae of the beetles were hiding in the roots of the plants. The adults emerged, laid eggs in his lawn, and have been spreading westward ever since. As with so many insects (and plants), natural controls are not in place when removed from their native range, leading to a population explosion. Females give off a pheromone while eating that attracts males to the area, which results in a mating/eating frenzy. They can fly over 5 miles in search of food, mates, and places to lay their eggs.

Speaking of food....what do they eat?

Adult beetles will eat over 300 species of trees, shrubs, plants, and fruits. Read this  article for an abbreviated list of preferred and hated foods. In my yard, they tend to prefer the New Jersey Tea shrubs (see the above picture). They focus on eating the portions of the leaves between the veins, resulting in a "skeletonized" appearance. In large numbers, adult beetles can decimate a tree or shrub. 

Where do they start their lives? 

Right now, in early July, adults are mating and laying eggs 3-4 inches below the surface of the soil. They prefer well-irrigated expanses of non-native turf grass. That's right, their larvae (or grubs) prefer to eat shallow grass roots. Think back to the story of my family gathering over the 4th of July holiday...they lived on the 18th fairway in a golf course community. LOTS of well-irrigated turfgrass. With up to 40 million acres of North America covered in lawns, we've created a smorgasbord for Japanese beetle larvae. Not only do the grubs damage lawns, but obviously the adults are causing massive damage to orchards, agricultural crops (soybeans), and homeowner's landscaping.

Control Methods

As I began researching control methods for Japanese beetles, I came across countless articles advocating everything from the "drown 'em in soapy water method" to the application of insectides to the introduction of bacterias. For more information, including sampling methods to determine the level of infestation in your lawn, read this factsheet from the University of Illinois Extension Office. Personally, I prefer to not introduce insecticides or bacteria, since many have harmful effects on beneficial pollinators or are just not very effective, and instead leave a tupperware bowl of soapy water near my shrubs to drown the beetles after I've plucked them off, usually first thing in the morning or in the evening when they're not as likely to fly away.The one method that you should steer clear of is pheromone traps, as they have been found to definitely attract beetles to the area, but in such large numbers that the majority aren't trapped. The beetles simply land nearby, and begin to eat/mate. 

In all of the articles that I read, only one pointed out the most obvious way to deal with the Japanese beetle problem....the reduction of turfgrass. Take away the majority of the larvae's food source, and a common sense result should occur. This information was found in the fabulous book written by Doug Tallamy that many of us are familiar with, "Bringing Nature Home." The reduction of lawn grass is also an objective of the Conservation@Home program. Not only does turfgrass require large amounts of chemical and water resources to keep it flourishing, it also attracts pest insects such as Japanese beetles. Look at your lawn strategically, and figure out where you can reduce the square footage of turf and replace with native plants. Think of it as your patriotic duty, as well as educating others. We can make a difference, and actually meet our brother's girlfriend's parents without turning into the Japanese beetle police.

Meet Heather Williams, a recently certified Conservation@Home property in Woodstock. Heather's property is found near Ryder's Woods, a 23-acre oak savanna owned by the city of Woodstock and managed by TLC. Because of its location, Heather has introduced numerous native woodland species over the last 14 years that have flourished and spread throughout her property. She has even shared plants with her neighbors, educating them about the benefits of landscaping with natives. She recently dug out a small area around a gutter output as an experimental rain garden after noticing small gulleys forming during rain events (see picture above right). It is so successful that she wants to add more rain gardens to other areas of her yard! Heather is a longtime TLC volunteer and member, but her introduction to the Conservation@Home program was actually a surprise. Her fiance, Scott McKeever, saw an article in the Woodstock Independent about the program, and knew that Heather's longtime passion for ecological gardening would qualify their property. He scheduled a site visit and surprised Heather with the yard sign and certification! What a great idea, Scott! Think about the gift of backyard conservation for your loved ones, because who really needs another scented candle?!

Remember that you can encourage homeowners, businesses, and other community groups to use the Conservation@Home ideas on their property, big or small. TLC is happy to offer presentations on C@H and many other environmental topics. Call 815-337-9502 or email Sarah Michehl at [email protected]. As the season progresses, email us updated pictures of your environmental features!