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 before considering next steps.
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 applying 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.
Photograph by David Cappaert, Michigan State University
Photograph by Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation