The Never Ending Saga of a Japanese Invasion

     One of the recent common questions that have been asked in the garden center of late has been, "WHAT, are those metallic looking bugs and are they actually eating my plants?"
If you haven't seen them yourself, maybe you have seen some damage like this?

     Those metallic insects and this kind of damage is none other than, The Japanese Beetle!
Popillia japonica as it is commonly known throughout the eastern half of the country, and probably many other parts of the world. It is just over one half inch long and just under one half inch wide. They are an iridescent copper and green color.

Photo Courtesy of WashingtonTimes.com

     It is not very destructive in Japan, where it is controlled by natural predators, but in North America, it is a serious pest of over 200 species of plants, including Rose Bushes, Grapes, Peaches, Crape Myrtles, Apples, and others.
     If you have ever complained about quarantines being in place, here is an example of why they exist. As the name suggests, the Japanese beetle is native to Japan. The insect was first found in the United States in 1916 in a nursery near Riverton, New Jersey. It is thought the beetle larvae entered in a shipment of iris bulbs prior to 1912 when inspections of commodities entering the country began. "The first Japanese beetle found in Canada was in a tourist's car at Yarmouth, arriving in Nova Scotia by ferry from Maine in 1939. The destructive rest, as they say, is history.
      The eastern U.S. provided a favorable climate, large areas of turf and pasture grass for developing grubs, hundreds of species of plants on which adults could feed, and no effective natural enemies. The beetle thrived under these conditions and has steadily expanded its geographic range.
The life cycle of the Japanese beetle is typically one year in most parts of the United States. Eggs are laid in the soil one to four inches deep in mid to late summer and hatch after about two weeks. The young grubs feed primarily on the roots of lawn grasses until the onset of cold temperatures where they go deeper into the soil for the winter.

Japanese Beetle Grub-Photo Courtesy of  https://georgeweigel.net

     As the soil warms again in the spring, the grubs move upward to resume feeding on roots until pupating near the soil surface in early summer. Adults usually emerge in early to mid-summer, but apparently this year they were not paying attention to the calendar, plus the weather has been so crazy here, who really knows what time it is!?

     So, they are here. What to do about them?
I will cover a few ways, from least toxic to the nuclear option.
If you have a small yard or a light infestation, you can just pluck the critters off and drop them in a bucket of soapy water. Leave this bucket out where the other beetles can see it, there is some evidence that the carcasses of other dead beetles may repel new invaders.

Photo Courtesy of Johnson County Extension - Kansas State University

    Traps are sold widely for Japanese beetle monitoring and control. Traps are highly attractive and draw beetles to them over large distances, so putting a trap in your yard will draw beetles from the surrounding landscape. Many of the attracted female beetles do not get trapped and end up landing on foliage nearby and feeding or mating then laying eggs in the soil near the trap, this creates a hot-spot for next season. So this may not be a good idea.

     Milky spore, Paenibacillus popilliae, is a bacterium that, when present in the soil, can help in the control of the grubs. You would need to get your neighbors to apply this also because such a large area needs to be treated for a significant impact on the beetle population, it is usually not an effective treatment for individual homeowners.

     Neem Oil can be useful. It is labeled for organic use, it will suffocate some, has some repellent activity by deterring feeding and it can disrupt the reproductive cycle. It is actually interesting how this oil works. Neem enters the system and blocks the hormones from working properly. Insects "forget" to eat, to mate, or they stop laying eggs. Some forget that they can fly. If eggs are produced they don't hatch, or the larvae don't molt. Hence, the cycle is broken. If you use it every year, you eventually will dwindle their numbers. Make sure you read the label and don't apply if the temperature is over 75 degrees. Apply either early in the morning or early evening. Spraying as many of the insects as possible.

     Getting into the nuclear options and these should be a last resort. Pyrethroid products such as Bayer Advanced Insect Killer and Permethrin products such as Spectracide Triazicide Insect Killer for Lawns & Landscapes Concentrate generally provide 2-3 weeks of protection.
     Carbaryl or better known as Sevin dust and others, provides immediate control of beetles present during the application and affords 1-2 weeks of protection . This is a stomach poison, so if beetles eat treated foliage they will also receive a higher dose. This can be a good control of Japanese beetles since they eat so much that a strong dose of insecticide is taken up. However, you, your family and the environment are also exposed to this poison. There is a threshold of the amount of damage that can be tolerated to your plants. I only recommend the nuclear option if that threshold has been surpassed. Make sure you read and follow the directions on the label, it is the law!!

     I foresee myself getting ready to pull the nuclear option. This is what my grape vines look like:

     I can't seem to get home in time from work to catch them and use the neem, so I will probably put down some Sevin dust in hopes that will work.

     As always, if you have any questions concerning this or any of my other articles, feel free to e-mail: TheCitrusGuy@netzero.com
You can find me on Facebook as The Citrus Guy or my new Website
Happy Growing!
Darren