Life Cycle: Adult female Japanese beetles lay eggs in July beneath wet lawns. Upon hatching, larvae feed on the sod roots and overwinter until the following summer. In June, the larvae pupate and adult beetles emerge to feed above-ground.
Damage: An extremely destructive pest, Japanese beetles feed on every part of the plant. The beetles skeletonize leaves and consume flowers and fruit entirely. Hundreds of varieties of plants can play host to this non-selective pest.
Control: Controlling Japanese beetles is a challenge this time of year as new adult beetles emerge from underground daily over several weeks. In small quantities, beetles can be manually removed from plants and dropped into a bucket of soapy water. Check plants daily to look for symptoms of this pest. Mornings are the best time to observe as beetles are slower and easier to catch.
There are many traps available that lure Japanese beetles into a container where the pests can be gathered and disposed of. However, some sources caution against using traps as the pheromones used to attract the beetles can draw in even more beetles than would naturally appear. Not all of these beetles may end up in the traps and the result could be greater damage to the plants.
Insecticides such as cyfluthrin (Tempo), bifenthrin (Hi-Yield Bug Blaster II) and cyhalothrin (Bonide Beetle Killer, Spectracide Bug Stop Indoor + Outdoor Insect Killer, Spectracide Triazicide, Bonide Caterpillar Killer) can be used for Japanese beetle control with about two to three weeks protection. Carbaryl (Sevin dust) can also be effective but only for about one to two weeks. The downside of using such products is they will also eliminate parasitoids and other natural predators.
Neem products (Natural Guard Neem-Py, Fertilome Triple Action Plus) and Pyola (pyrethrins in canola oil) can offer control for three to four days. (Cynthia Domenghini)