I have a gardening friend who just moved from another part of the country to west Kentucky. I have had so much fun teaching her about the different flora and fauna she's encountered in her new home. We're both nature lovers and it isn't unusual for her to call with a new discovery for identification help.
One day, the phone rang and my excited friend was on the other end of the line. She was gushing over the most beautiful insect that landed in her garden. This lovely creature was described as a fantastic copper-green with little white spots along its outside edges...uh-oh, I thought. I asked if it was about the size of a penny and she confirmed that it was. Stomp it quick! Nooooo...she cried! It was difficult to convince her that this was a horrible pest and would lay waste to her garden along with its many brothers and sisters.
Popillia japonica, commonly known as the Japanese Beetle is a significant insect pest in eastern North America. It is theorized that larvae arrived on the East Coast about 1912 in a shipment of iris roots and over the next few years, adults were discovered in both the US and Canada. Over the next decades, the population increased due to lack of natural predators and they became a serious agricultural and garden pest.
One beetle alone, isn't much of a threat and doesn't cause much damage, but this species tends to congregate in vast masses and can defoliate a garden rather quickly. Japanese beetles skeletonize leaves by chewing the soft leaf parts between the tougher veins, leaving the plant unable to process chlorophyll and retain nutrients. They are also partial to flower buds and find roses a treat. The first beetles to arrive in a tasty new spot secrete something called a congregation pheromone. This is like a 'Bat Signal' for other beetles to hurry on over to enjoy the goodies. Even if the first beetle is killed, if it has released its pheromone, others can still find the spot. It is quite possible to see hundreds of these insects clumped together on a plant vying for the best morsels.
Female beetles eat, mate, lay eggs and repeat the process. They can lay upwards of fifty eggs during each season. They burrow into the ground to lay their eggs and the the resulting larvae actually feed on plant roots, making this a double-duty pest.
The best way to control these beetles is to hand-pick adults into soapy water or apply an insecticide. If you have an infestation heavy enough to warrant an insecticide, Neem based products are the safest for people and pollinators. If you do use poison, please take the utmost care to protect our pollinators when using it. We do not need to lose any more bees! Grubs can be controlled by spreading products on your lawn that alters their life cycle. Milky Spore has shown to be somewhat effective in this application.
Many garden centers market Japanese beetle traps that are baited with an attractant. Use this if all else seems to fail as studies indicate that the traps tend to lure even more beetles to the area and they settle on nearby plants to feed instead of falling in the traps. Use at your own risk.
The moral to this story is that pretty doesn't always mean friendly. If you encounter a new insect in your garden, it is always desirable to identify it before labeling it a friend or foe.
Thumbnail and top banner courtesy of Wikimedia Commons, the other images are my own.