Some uninvited guests might be living rent-free in your garden.
Japanese beetle season is in full swing in Northeast Ohio, as the pests emerge from underground in the summer months. The critters feed on a wide variety of plant species, commonly posing a threat to landscapes and gardens.
“Beneath the soil, growing grubs gnaw on grass roots causing turf to brown and die,” according to the U.S. Department of Agriculture. “Adult beetles feed on more than 300 ornamental and agricultural plants. They chew large, irregular holes between leaf veins, which makes the leaves resemble a piece of lace.”
Zachary Loraditch, a certified arborist for the Davey Tree Expert Co. in Kent, said the Northeast Ohio area hasn’t been hit as hard by the species this year, but vigilance is still important.
“This season, we’ve actually been a little bit lucky,” he said. “They’re not quite as bad for us this year as we’ve seen in some years in the past, but that’s also relative to that insect. It loves to do its thing, even when populations are low.”
What does a Japanese beetle look like?
Japanese beetles have a distinctive appearance, identified by a metallic green color in the head area and a coppery hue on its wings.
“Japanese beetles (Popillia japonica) were first found in the United States in 1916, after being accidentally introduced into New Jersey,” according to the University of Minnesota Extension. “Before then, this insect was restricted to Japan where it is not a major pest.”
Adults range from around one third to one-half of an inch in size, and have a lifespan of 30 to 45 days, but their reproduction rate is high.
“The white, wormlike larvae — also known as grubs — that hatch from the eggs are the nation’s most pervasive turf pest. Grubs devour grass roots, making water absorption impossible and ultimately killing the grass,” according to the Arbor Day Foundation.
Skunks, raccoons, moles and armadillos also enjoy digging up and feeding on the grubs.
Which plants do Japanese beetles target?
Loraditch said as a general rule of thumb, Japanese beetle populations typically surge in the month of July before evening out in the following months.
“As far as insects and pests go for us here in Northeast Ohio, it’s kind of one of the big ones for us,” he said. “It’s a mean little bugger that likes to show up in a lot of folks’ landscapes right around (Independence Day).”
The insects tend to favor certain types of plants, Loraditch said, so proactively taking stock of the plants in your garden is key.
“If you’re a homeowner and you’re thinking about the insect or you’re worried about the insect, think about what plant material you have in your landscape,” he said. “You’re looking for things like … ornamentals like cherries or plums, Japanese maples, some crab apples. Japanese beetles love those guys. Sand cherries, hydrangeas, some of the shrimps … can be pretty susceptible to the insect.”
How can gardeners fend against Japanese beetles?
Loraditch said some popular options for managing Japanese beetles can do more harm than good.
“It’s a popular sentiment for homeowners to pick up some pheremone traps. … They’re something that tends to be popular amongst homeowners if they don’t learn too much about it,” he said. “Generally on our side of things, we don’t like seeing those because while the Japanese beetles are attracted to the pheromones on that, you’re also attracting Japanese beetles from anywhere that’s nearby over to your property specifically.”
Loraditch said if Japanese beetles are present on a property, getting a pesticide treatment done is a good bet for mitigating the population.
“You kind of want to do multiple sprays over the course of the summer season because those populations can try to resurge” he said. “If (you) do see Japanese beetles on the property, having a treatment of those guys, doing a spray to get some control of them is important.”
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