What are Japanese beetles?
Japanese beetles are invasive insects that were introduced to the United States in the early 1900s. They’re recognizable by their green heads and bronzy colored backs, with small white spots along their abdomens. They measure about a quarter of an inch in size, and often travel in colonies.
When do Japanese beetles feed?
You'll most likely spot the most Japanese beetles in late June through mid August. In some years, you may notice an abundance of Japanese beetles, and other years, very few at all. Local climate conditions can play a big role in the amount of Japanese beetles around. For example, dry soil makes larvae unviable.
Where do Japanese beetles show up?
According to the U.S. Department of Agriculture, Japanese beetles are most prevalent in states east of the Mississippi river, as well as states bordering the Mississippi - like Iowa.
Japanese beetles feed on tons of different plant species - they're not picky. You'll most likely see them feeding on the foliage of plants though, and you’ll see lots of tiny holes in the leaves they’ve eaten. They can defoliate the plant in the process, so your garden plants may not look as pretty once the bugs are done eating. It's also not unheard of for Japanese beetles to feed on the flowers or fruit of plants as well.
How to prevent Japanese beetles
Dr. Laura Iles, Director at the North Central Integrated Pest Management Center, said "there's no way to win."
Iles says the best thing to do is to pick them off individually, or dispose of an entire leaf that's being consumed. She says people try screening, netting, and insecticides, but none are a sure thing. Iles also says that Japanese beetle traps do exist, but they can end up attracting a lot more beetles to your garden in the process.
If you're just starting your garden, Iles says there are a few plants that Japanese beetles are known to be really interested in, including roses, grape vine, crab apples, birch and linden trees.
When should I start panicking?
The good news, if you’re a home gardener, is - you don’t need to. For home gardeners, there is rarely any long term harm - the damage is primarily cosmetic. Commercial growers should be more worried though, especially for crops like soybeans. But generally speaking, though Japanese beetle damage can be an eyesore, the plant - and any fruit produced - is still healthy.
