Keep Japanese Beetle at Bay Next Year

Japanese Beetle

This year, the Midwest experienced major defoliation due to a small pest called the Japanese beetle. Contrary to its name, the Japanese Beetle is not as problematic in Japan as it is in the U.S., as Japan has more natural predators which control it. In the U.S., this pest wreaks havoc on nearly 200 species of plants, skeletonizing their foliage and causing rapid defoliation. Large numbers of beetles are being found on ornamental plants and on crops, indicating that a wave of insect damage and defoliation is building, and that this Japanese Beetle problem is getting more severe.

By planning ahead and putting a treatment plan in place, you can prevent Japanese beetles from infesting and damaging your trees and plants as severely next year. You can change the expected devastation next year and reduce the damage. Read on for our recommendations.


History of the Japanese Beetle

The Japanese beetle is native to Japan, but arrived in New Jersey before 1916. It’s suspected that the beetle larvae entered our country in a shipment of iris bulbs several years earlier, and before inspection of commodities began.

The infestation quickly worsened, and now, nearly every eastern and mid-western state fights the pest off yearly. Typically, Japanese beetles hatch around July 4th, providing most of the summer for them to cause plant damage to farms, forests, flowers, and ornamental trees and shrubs.

Though it is small, measuring just 1.5cm long, Japanese Beetle poses a serious problem. If you see an iridescent copper and green colored beetle, contact your local arborist for confirmation (and visit for pictures of the pest) before considering next steps.


Japanese Beetle Map



Recommended Treatment Plan

Arborjet recommends a few different action plans depending on the location of the infestation, weather factors, severity, and plant material.

AzaSol has antifeedant properties against Japanese beetle, and they tend to avoid the foliage because of the residue. Use as either a spray or via tree injection. Because this pest is so difficult to control, AzaSol treatments must be reapplied numerous times throughout the adult feeding season if sprayed, and once every thirty days by injection. We recommend injecting AzaSol by injection initially and then following up within 14 to 28 days with IMA-jet post-bloom on flowering plants to fight persistently feeding pests.

Many flowering species would benefit from ACE-jet depending on timing of the treatment. Those interested in this method should apply treatment after flowering and should expect around 30 days of activity. This method generally works best when Japanese beetles are already active on trees (after July 4th) and may be coupled with a longer lasting IMA-jet injection. When used alone, IMA-jet will provide season-long protection on non-flowering species like birch trees, but must be applied post-flowering on other species.

IMA-jet, AzaSol, and ACE-jet are all active against Japanese Beetle. The residual activity of IMA-jet often makes it the most attractive and efficient option for treatment, depending on the plant infested.


Next Steps

As you wind down from a particularly devastating summer of pest infestations across the country, it’s essential to put a protection plan in place for next season. Though it may not be effective to treat this late in the season, an early game plan ensures the best chance to fight this pest next season and in the years to come.

Connect with your Arborjet Regional Technical Manager or service provider today to discuss the best method for you. For more information on Japanese Beetle and a host of other pests and diseases, browse our website and follow us on Facebook, Twitter, LinkedIn, and Instagram.