Category : Invasive Beetle

Garden Invasive Beetle

Beetle Management

Siobhan Cave

Insects, bugs, creepy-crawlies, and all of those little creatures that cause you to look down at your arm when you feel the tickle of tiny legs on your skin and send yourself into furious flapping and flailing—they have an important role in your garden, regardless of how weird (spiders), gross (large spiders), and upsetting (large spiders that are hairy and move quickly) you might find them (gross, spiders are gross).

Well, most do, but all too frequently a perfectly harmless species hitches a ride from one place to another, or sadly, is introduced deliberately in the hopes of increasing resources or managing an ecological problem, only to set up shop and become a tremendous threat to native species and a royal pain in our you-know-whats.

Japanese Beetle
Japanese Beetle

Japanese beetle came from (you guessed it Japan!)

Of no creature is this truer than the arch-nemesis of the home gardener, Popillia japonica, a hitchhiker from mainland Japan that first appeared in this country in the early 1900s.  We know him lovingly as the Japanese beetle, or by a litany of personal pet names we have developed upon the discovery of his handiwork that we aren’t going to repeat in this post. His craftsmanship is pretty easy to identify once he’s moved into your yard, especially as he tends to want to eat the same things you do.  Peaches, plums, cherries, corn, grapes, and berries are some standout favorites of his, but he is known to nosh on as many as 300 varieties of flowers, fruits, vegetables, and trees. Usually, he sits on the foliage and chews all of the leaf out of the leaf, leaving behind a skeleton of veins, but if he’s really in a mood to tap dance on your nerves, he’ll drill holes through all of the best specimens on your fruit trees, leaving you with his brown-spotted and gnarled rotting scraps.  Got roses? Perfect! Some of the most devastating damage ol’ JB reserves is for your rose bushes, where he’ll delight in chewing up foliage and flowers.

Japanese Beetle
Japanese Beetle

The truly frustrating thing about this pest is that it’s really good at being a pest.  It is effective at destroying your yard even before it has its adult beetle form. After mating, Japanese beetles deposit their eggs into the surface of your soil.  The eggs become grotesque little grubs that burrow down deep into your turf to wait the winter out. When temperatures rise, they slowly climb up to the surface, using the young and tender roots of your freshly reseeded lawn as a buffet. This is what causes brown spots and dead clumps all over your grass areas.

Controlling this invasive will require an attack on two fronts, as eliminating beetles above ground won’t necessarily help you with your subterranean problem.  Unfortunately, even effective use of Japanese beetle control methods will only manage the pest on your property—Japanese beetles can travel miles to get to where you find them, so you’ll have to use these strategies every season to eliminate visiting beetles and limit their use of your lawn as a nursery.

Remove beetles by hand

Like weeds, when it comes to adult beetles, the best thing you can do is remove them by hand.  Japanese beetles are easy to spot, thanks to their shiny green and gold bodies, and you’ll usually find them chowing down with about twenty of their friends.  Clumps of feeding beetles are very easy to shake right into a bucket of hot soapy water, which saves you, your pets, and your plants from exposure to pesticides.  If your property is small and the damage seems to be localised to certain areas, this is definitely the best way to get rid of them. Bonus to those with or considering getting chickens: many hen hobbyists report finding an irresistible snack in their buckets of collected Japanese beetles—their chickens just can’t seem to eat enough of them. Turning some chickens loose in your infested areas might be a good natural solution to your beetle problem.

Japanese beetle traps are a popular passive way to collect your beetles, but as many will tell you, the attractant in the traps that entices them inside seems to do a whole lot more enticing them into your yard in general.  You will assuredly be up to your eyeballs in captured beetles, but be mindful of the beetles you’ve attracted that didn’t end up in the trap. Be prepared to use another control method in conjunction with the traps, and for beetle traffic in your yard to increase once you’ve set them up.

Closeup Rhinoceros beetle, Rhino beetle, Hercules beetle, Unicorn beetle
Closeup Rhinoceros beetle, Rhino beetle, Hercules beetle, Unicorn beetle

Consider placing a fine mesh protective barrier over at-risk plants, like rose and berry bushes, just before you would begin to see Japanese beetles in the late spring or early summer.

If your problem is dire or widespread, you will have to resort to pesticides keep the population in check.  Japanese beetles can be killed by several ingredients, like permethrin and carbaryl, that are found in many popular pest control sprays.  Neem oil also proves effective against the beetles if you would rather use a natural product.Take caution with any chemical you choose to use in the garden.  Use only the amount you need to get the situation under control (many pesticides that kill Japanese beetles are non-selective), and only use products designed for use with edibles on anything you plan on eating later.

Removing beetle grubs

Removing Japanese beetle grubs from your lawn is done with soil additives, most popularly Paenibacillus popilliae, bacteria that causes milky spore disease.  Once consumed and absorbed by the grubs, the bacteria can kill the grub in less than a month, using its remains to release more milky spore into the soil. This cycle allows you to apply the spore to your lawn once and inoculate it against grubs for several years before reapplication is necessary.  Milky spore is a powdered product that is easily applied to your lawn with a cardboard tube in four-foot spots.

Like milky spore, parasitic nematodes may be added to the soil to seek out and eliminate grubs along with several other unwanted pests.  Both methods of control are harmless to humans, pets, and wildlife.