What can be used to effectively repel Japanese beetles from plants?


What can be used to effectively repel Japanese beetles from plants?  Presently I use a trap & hand pick beetles several times a day.


Katherine Garland, Horticulturist

I’m sorry to hear you’re dealing with a heavy “crop” of Japanese beetles this year. Now is when the adults are most actively feeding and mating, so you can potentially see hoards of them on a variety of plants.

Here are some great management tips from our bulletin on Japanese beetles:

“Managing adult Japanese beetles is challenging because of the large numbers that can occur throughout the summer. A combination of approaches is suggested. Consistent handpicking of the adults can help protect your plants from ravages of this pest. A coffee can, about a third full of soapy water, can be used to collect the beetles.

Although controversial, you may want to consider pheromone/bait traps as part of your management strategy. Be sure to place traps at least 50 feet away from the plants you want to protect. Also, do not wait for the trap bags to completely fill before emptying. Poorly maintained traps can be a liability instead of a help. In spite of some evidence that they may draw in more beetles than would normally be present, some gardeners have reported positive results with the traps.

Protective barriers (e.g. spun-bonded material) can be used to protect susceptible plants during massive influxes of beetles.

In New England, beneficial nematodes (best application time:  last three weeks of August) have been shown to be somewhat effective in managing white grubs. Milky spore has given spotty results and is not recommended.

Foliage can be protected with sprays of pyrethrins, neem, Kaolin clay (Surround), cyfluthrin/imidacloprid, malathion, or carbaryl (Sevin). Repeat applications, if permitted by the label, are often necessary for protecting plants from this pest.

Japanese beetle white grub management efforts are most effective when control agents are in place when the white grubs are small and feeding in the turf root zone. White grub insecticides, such as chlorantraniliprole (GrubEx1), most effective when applied mid-April through May,  imidacloprid (Merit) or halofenozide are also options to consider (best results obtained from June or July application). Targeting the grub stage in hope of relief from the adult beetle often leads to disappointment.

Be sure to read and follow label instructions on all management tools (traps, nematodes, and insecticides).”

We have a great video that summarizes management options: https://www.youtube.com/watch?v=aEUfoW1Yrz8&t=1s. Here’s a link to the bulletin I mentioned: https://extension.umaine.edu/ipm/ipddl/publications/5037e/.