The Japanese beetle (Popillia japonica Newman) is an invasive species that is slowly making its way across the United States. While they may not be a threat to human health, their notorious appetite can do serious damage to both lawns and gardens. If you're, like most people, scrambling to figure out how to get rid of Japanese beetles, there are ways to control them before they become too big of a problem, but it takes some effort. So if you're curious about these buggers and want to learn more about how to deal with them, read on!
Japan to America: A story of a century-long invasion
The United States is home to a whole lot of pesky invasive insects. How many exactly? Well, you might be surprised! According to an estimate, there are about 4,300 species of invasive insects in the US. The Japanese beetle is the most devastating of all invasive insect species in urban communities.
The Japanese beetles, as you can tell from its name, originally belonged to Japan before making America their second home. They were first introduced, and that too, accidentally, within a shipment of Japanese irises bulbs in the early 1900s. Later, they were discovered at a New Jersey plant nursery in 1916.
In their native home range, they have natural predators which keep the population of these pesky insects at bay. The absence of Japanese predators and optimal climatic conditions helped these insects to successfully thrive and proliferate in eastern America; where they're loathed by just about everyone.
By 2015, they had fully or partially established themselves in more than 70 percent of the US and beyond, in West and North. They've now infested Canada, Italy, Portugal, western Russia, Korea, and some parts of India as well.
As with many human-induced invasions, our love for lush green lawns that are watered regularly is what has provided perfect conditions for Japanese beetles' larva to thrive without being bothered by any predators. Today, this ravenous bug is the most widespread garden pest in the US.
Identification of Japanese beetle
Despite the damages, it is hard not to be impressed with these bugs' looks. The adult beetle is oval-shaped and only about ⅜ inch long. The head and thorax are covered in a fluorescent, metallic green shell and shiny copper-brown wings that shimmer as if an alien life form.
They have six legs, two antennae that look like tweezers, and five to six tufts of white hair on each side and rear of its body. These tufts are the key to identifying the flyers from other beetles.
The grubs or larvae look very similar to chafer beetles. They're about ⅛ inch long, white to cream-colored, C-shaped grubs.
The Japanese beetles are known to feed on more than 300 species of plants. While the grubs feed on grasses, the adult beetles skeletonize leaves, leaving decimated gardens and dying lawns behind.
Life cycle breakdown to understand the destructive powers of Japanese beetle
The damage caused by Japanese beetles is unmatchable because it occurs over multiple life cycle stages. It takes about a year to complete.
The cycle begins when the mature beetles lay eggs that hatch midsummer, and the larva grows into tiny, comma-shaped white grubs. The grubs move to the surface of the soil during summer, feed on the grasses and other roots, and later move deeper in the soil during cooler temperatures. They emerge as adults the following year.
The lifespan of adults is shorter, only about 40 days, but they have got a voracious appetite. What's more concerning is that they feed in small groups. The first to appear release a scent, technically known as congregation pheromone, to gather a mob of adult leaf munchers.
They target flowers and fruits of more than 300 kinds of landscape plants, ornamental plants,
including garden roses and blueberries, leaving them skeletonized. The damages are evident as the random lawn patches turn brown and die.
Since they feed on both above and below the soil, they've become a nuisance for farmers and lawn owners across America. The control and eradication of these invasive insects require action during all stages of development. So, let me breakdown the life stages for you:
Egg: In late spring, mature beetles lay small, oval, white eggs in the soil. The eggs might absorb moisture and grow rounder by the day.
Larvae: This stage is the most damaging of all. The white grubs have V-shaped bristles or tufts on the underside of their abdomen.
Pupae: The intermediate, non-feeding stage is where the grub transforms into a beetle. The pupae start is cream-colored and develops into a reddish-brown adult beetle.
Adult beetle: The adult beetles are about ⅜ inch long, with shiny shells and wings. Adults emerge from the ground between May and June and live for about 30 to 40 days, during which they actively feed and reproduce.
The females feed only for a couple of days, then tunnel down each time to lay their eggs near grass, or American turf, the favorite food of beetle grubs. By the end of the cycle, each female Japanese beetle will have laid about 60 eggs, and, thus, the infestation cycle begins all over.
Damage from beetle grubs to below the ground
It is very likely you have a pest in your lawn when you notice the dead patches from which you can easily pull large clumps of grass out of the ground. After hatching, the grubs of Japanese beetles dig up to a foot in soil and become dormant.
When the temperature warms, the curled, c-shaped grubs crawl back to the surface again and actively feed on the roots of the American turf-grass and other plant species, ultimately killing them over time. Their munching significantly reduces the ability of grass to absorb water and nutrients from the soil, changing it to brown, dead turf that can be pulled off like a loose carpet.
Today, the Japanese beetle larva has become one of the most devastating turf-grass pests in the US. According to one estimate, it costs the US an annual sum of $234 million to replace turf and control beetle larva.
Damage from adult Japanese beetles above the ground
The most widespread of the damages occur on the surface of the ground. Japanese beetles are ill-famed for damaging over 300 plants species in North America. The various flowering plants, trees, and vegetable crops susceptible to the attack of Japanese beetles include;
The adults feast on the foliage of plants, targeting the tender plant material between the leaf veins. This feeding behavior is called skeletonization, which turns the plants brown and decimated. Most of the damage is superficial rather than permanent. Healthy plants can tolerate the beetle infestation, though the spring blossoms are often ruined.
Control & Prevention of Japanese beetles
Early management and control of Japanese beetles are necessary for effective control. Be on the lookout for beetles in your garden or backyard. The ideal timing for action depends on what stage of the beetle-life cycle you’re trying to control. Since they have no natural predators in the region, you need to use one of the many control methods.
While the grouping makes beetles powerfully destructive to plants, the mob is an easy target for control and eradication measures. However, some beetle control methods might require some hands-on effort.
If you’re experiencing severe Japanese beetle infestation in your garden and lawn, about a dozen in 1 square-foot section of turf, consider treating them with proper grub control techniques.
Nida Riaz is a freelance blogger based in Pakistan. She started writing about her passion for the environment when the world came to a stop in early 2020.