Japanese Beetles Are Back!

I’m in North Central Alabama, and it’s the middle of June. Leaves on my tomato plants looked like grandmother’s lace curtains, all frilly and full of holes. Got a container of soapy water and started searching, it didn’t take long to find and dump the culprits in their last ‘flight destination’.

Japanese beetles (Popillia japonica)

Japanese beetles skeletonizing a leaf.

Japanese beetles have arrived, for some they’re been around for weeks.
While roses are primary targets of these leaf-eaters, other potential munchables include grapes, hops, canna, Crape Myrtle and Birch trees.
Damage done by the adult beetles is aimed at foliage, the beetles eat material between the veins, giving the leafy, “skeletonized” appearance typical of Japanese beetle damage. In addition, beetle larvae feed on grass roots, causing damage on their way to the surface as adult insects.
Popillia japonica (Japanese beetle) came to North America from its native Japan in the early 1900s. By 2015, only 9 states in western U.S. were considered free of the invasive pest but many suspect it’s a matter of time before the beetles are shared by all fifty states.
Japanese beetle activity is at its height during June, one reason why some confuse Japanese beetles with the larger and less populous June beetle. And though the J-beetle can be found here and there throughout the summer, by the end of July populations and resulting damage have tapered off, at least from the adult beetles.

Japanese beetle (Popillia japonica)

Japanese beetle (Popillia japonica)

However, eggs laid by the adult female hatch, and it is these newly hatched grubs that burrow into the ground, feeding on grass roots to the point significant damage can occur. In addition to damage directly attributed to the grubs, other critters like the tasty grubs, providing a food source for hungry skunks, raccoons, and armadillos. Keep in mind watering the lawn creates a favorable environment for the grubs, which in turn attracts other critters, part of the food chain.
The most effective Japanese beetle control is a two-fold approach, one for adults, the other for the larvae or grubs.
Adult beetle control, as mentioned earlier, can be as simple and “organic” as dropping them in soapy water before they can gather their wits and fly away. The other extreme is the use of chemicals, but any product listed for control of adult Japanese beetles should be used in accordance with label directions to avoid unnecessary elimination of non-target insects that we want in our gardens. Other control options such as Japanese beetle traps are more controversial, as some research indicates beetles attracted to the traps damage plants near them instead of becoming victims of them.
The larval or grub stage are big eaters, but they’re very susceptible to milky spore disease, a biological control available in powder form that can be applied to lawns. The upside of milky spore – it targets Japanese beetles, low toxicity to other organisms. The downside of milky spore – it can take a couple of years to establish the bacterium for maximum protection against the larvae.
For an insect smaller than a thumbnail, this species of scarab beetle can do a lot of damage. And like it or not, we plant what they love to dine on.
Like most pests, they’ll come back next year about this same time. Timing control to start before adults emerge from the ground will help reduce their populations and subsequently damage to our gardens and landscapes.

By Sallie Lee, Urban Regional Extension Agent, Alabama Cooperative Extension System.  Contact Sallie at leesall@aces.edu.

The Alabama Cooperative Extension System (ACES) operates as the primary outreach organization for the land-grant functions of Alabama A&M and Auburn Universities. ACES is committed to affirmative action, equal opportunity and the diversity of its workforce.  Educational programs of ACES serve all people regardless of race, color, age, sex, religion, disability, sexual orientation, or national origin.

Alabama Extension

The Alabama Cooperative Extension System operates as the primary outreach organization for the land-grant functions of Alabama A&M and Auburn Universities and answers home-gardeners' questions each week on Birmingham Gardening Today.

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