The Japanese Beetle has made itself known in our area as a plant/shrub & tree leaf decimator! Many flowering roses, rose of sharon, fruit trees and hibiscus can be attractors of the japanese beetle. (there are more than 300 known varieties of plants that the beetle is attracted to)
To start at the beginning of a Japanese beetle’s life cycle – the eggs are laid 1-3″ under the ground by the female beetle in late summer. As the weather cools in the fall, the eggs become larvae and then grubs which then burrow further down into the soil for the winter. In the spring, grubs move up near the soil surface to finish feeding and pupate into adult beetles. One female can lay up to 60 eggs!
Adult beetles start to emerge from the ground in late June or early July. They can fly up to several miles to feed. Adults will feed primarily in July and August, although some may be active into September.
Beetle-damaged leaves emit feeding-induced odors that attract other beetles. So, the more damage that is caused to your leaves and plants, the more beetles will show up to feast. This often results in large clusters of beetles feeding and mating on particular plants while neighboring, equally attractive plants are only lightly infested. Japanese beetles are generally drawn to plants with large flower petals and foliage with a soft, smooth texture and a light sweet scent. (such as roses)
Some plants that the beetle has some aversions to are: Chrysanthemum, coreopsis, boxwood, dogwood, holly, peonies and lilac shrubs.
Ways to “Battle the Beetle”
Companion Planting: Plant repellent species alongside susceptible plants to mask their scents and discourage beetle infestations. Rosemary, nasturtiums, marigolds, chives, catnip and garlic are popular plant repellants.
Neem Oil: Not only can neem oil deter them from feeding on your plants, but also harm the beetles if they eat it. The best part is, if the Japanese beetles injest the neem oil, they will pass it down to the eggs, preventing them from hatching. This way, you’re protecting your lawn and controlling the Japanese beetle population resulting in a win-win! This needs to be done early in the season to have the greatest effect.
Get rid of the grubs: Grub-eliminating nematodes can help prevent Japanese beetle eggs altogether. Products such as Grub-B-Gon on your lawn in the spring and fall have also been proven to be beneficial in decreasing grub #’s from maturing into adults.
Soap solution drowning: Mix a couple tablespoons of dish soap with water in a small (approx. two cups) container. Empty beer or soda cans work well because the beetles have even less of a chance to escape. The soapy solution kills the beetles – they drop to the bottom and drown before they have a chance to release pheromones. Doing this on a regular daily basis is key to actually eliminating or decreasing beetle numbers. Swatting the bush or shrub and having the beetles fly away won’t get rid of the problem. They will just come back. You need to actually kill them to prevent them from laying eggs to overwinter and then hatch in the spring, bringing on another onslaught of this dreaded insect!
Sprays: There are very few sprays that are successful with detering or killing the beetles, but there are some that are worth a shot! One spray is made from cedar oil (red eastern cedar) which can be purchased from various on-line sites. When sprayed on the roses it will knock the beetles off and if you have your soapy bucket at hand, they will fall into the bucket and drown. The spray will help deter them from landing on the shrubs you have sprayed. Some additional sprays that have proven effective are ‘seven’ – essential oil sprays – Bug Tek spray – insecticidal soaps – Beetle B Gone, End-All and neem oil (be sure to spray your plants in the cool of the evening to prevent leaf burn in the hot sun)
Nip rose buds and spray rose bushes: Note that insecticides will not fully protect roses, which unfold too fast and are especially attractive to beetles. When beetles are most abundant on roses, nip the buds and spray the bushes to protect the leaves. When the beetles become scarce, let the bushes bloom again. Timeliness and thoroughness of application are very important. Begin treatment as soon as beetles appear, before damage is done.
Beetle Traps: Japanese beetle traps can be effective in some situations, but they also have drawbacks. While they attract large numbers of beetles, they may not be the best method for controlling infestations, and in some cases, can actually make the problem worse. Here’s a more detailed explanation:
Attraction vs. Capture:
Traps are very effective at attracting Japanese beetles, especially those baited with pheromones, but they don’t always catch all the beetles they attract, potentially leading to increased damage in the surrounding area.
While some of these methods aren’t a fool-proof way to protect your plants, it can keep Japanese beetles at bay. While these beetles won’t kill your plants, trees or shrubs, they can cause some severe damage. Taking preventative measures in the spring will help you have a beautiful, healthy lawn and plants in the summer—free of Japanese beetles!