How to Get Rid of Japanese Beetles in the Garden

Prevent Japanese Beetles From Eating Your Plants! [View web version]( [FOCUS]( [Phyllom BioProducts Logo]( [How to Get Rid of Japanese Beetles in the Garden]( Prevent Japanese Beetles From Eating Your Plants! Japanese beetles (Popillia japonica) are iridescent green beetles that carry a big threat because they feed on a wide variety of plants. We have a great solution for addressing this problem early, plus more tips on how to prevent Japanese beetles from eating your plants this season! [Ad - 300x250]( [Japanese Beetle] Use these tips to get rid of Japanese beetles. Photo Credit Crestock What Are Japanese Beetles? Japanese beetles do not discriminate when it comes to what types of plants they feed on, though they do have favorites (like [roses](). In fact, they are classified as pests to hundreds of different species. They are one of the major insect pests in the Eastern and Midwestern United States, causing monumental damage to crops each year. Prior to the beetle’s accidental introduction to the United States in the early 1900s, the Japanese beetle was found only on the islands of Japan, isolated by water and kept in check by its natural predators. In 1912, a law was passed that made it illegal to import plants rooted in soil. Unfortunately, the failure to implement the law immediately allowed the Japanese beetle to arrive in this country. Most entomologists agree that the beetles entered the country as grubs in soil on Japanese [iris]( roots. In 1916, these coppery-winged pests were first spotted in a nursery near Riverton, New Jersey. By 1920, eradication programs were dropped; the beetle proved to be too prolific and widespread. IDENTIFICATION How to Identify Japanese Beetles Japanese Beetles are ½ inch in length with distinct metallic blue-green heads. They have copper-colored backs, tan wings, and small white hairs lining each side of the abdomen. Japanese beetles usually feed in small groups. Prior to becoming adult beetles in late June, they are 1-inch-long, white, c-shaped grubs that live in the soil and feed on the roots of many plants. These grubs are often a problem in lawns. Once adults, Japanese beetles live only 40 days, but they are voracious. Japanese beetles attack plants in groups, which is why the damage is so severe. Most feeding starts in mid-to-late June in the North and mid-to-late May in the South. [Japanese beetles cause leaves to appear skeletonized] Japanese beetles cause leaves to appear skeletonized. Photo Credit: Ohio State University. Signs of Japanese Beetle Damage Japanese beetles feed on a wide variety of flowers and crops (the adult beetles attack more than 300 different kinds of plants), but in terms of garden plants, they are especially common on [roses](, as well as [beans](, [grapes](, and [raspberries](. Here’s what to look out for: - Unhealthy, Brown Patches in Lawn First come the Japanese beetle grubs (larvae), which damage grass when overwintering in the soil. The grubs feast on the roots of lawn grasses and garden plants. This can cause brown patches of dead or dying grass to form in the lawn, which will pull up easily thanks to the weakened roots. - Skeletonized Leaves and Flowers Then come the adult Japanese beetles which chew leaf tissue from between the veins, leaving a lacy skeleton. You’ll know right away when you see leaves that are “skeletonized” (i.e., only have veins remaining). ([Mexican Bean Beetles]( can also leave foliage skeletonized, though, so be sure to identify the beetle by their appearance as well.) CONTROL AND PREVENTION To manage Japanese Beetles in yards and gardens, the trick is to start early! Once these insects are present in large numbers, the problem is very difficult to manage. Here are 10 tips to prevent beetles: - Start at the grub stage! BTG or Bacillus thuringiensis galleriae (e.g., products such as grubGONE!) uses naturally-occurring soil bacteria. This bacillus ONLY targets certain lawn insect pests, such as Japanese Beetle grubs, before they become destructive adults. The grubs ingest the spores and the natural yet powerful BTG proteins as they feed in the soil. It is as effective as a chemical pesticide and works within days to weeks of application but is NOT toxic to beneficial insects, such as earthworms, bees, and pollinators; it will not harm people, pets, animals, or plants. BTG will kill not only Japanese Beetle grubs but also a variety of other destructive beetle larvae and grubs, such as Chafers, Oriental Beetles, and Billbugs, throughout the spring through fall seasons. To deter an infestation of adult beetles and kill the beetles that do infest your edible or ornamental plants, you can use BTG or Bacillus thuringiensis galleriae as a spray (e.g., product beetleGONE!). Like with the grubs, BTG effectively kills the adult beetles through a combination of the BTG protein and spores. One key to success is to start applying early: at the first signs of the adult beetle. Farmers and growers have stated that they believe BTG may reduce the attraction by early-arriving beetles of more beetles by inhibiting the effectiveness of the early arrivals’ use of their beetle-attracting pheromones. This product can be mixed in water and sprayed on edible garden plants, ornamental plants, and trees to kill Japanese Beetle adults or put into turf to kill the grubs. It can also be used dry as a mix into potting or garden soil to control beetle grubs. The product is registered with a zero-day pre-harvest interval, therefore, you can treat for beetles and pick your food the same day. There are no label restrictions for use around bees or flowering plants; therefore, it can be safely used while pollinators are active. There is also no toxicity to fish or aquatic life. - Hand pick early: Look for beetles in mid-to-late June or early July. In the early morning or evening, when beetles are more sluggish, knock beetles into a bucket of soapy water. Yes, it’s time-consuming, but it’s also the most effective way to kill these pests. Just be diligent. When you pick them off, put them in a solution of 1 tablespoon of liquid dishwashing detergent and water, which will cause them to drown. Do this daily, as the chemical trail of beetles attracts more beetles. - Protect with row covers: Use [row covers]( during the 6- to 8-week feeding period that begins by mid-to-late June in the North and mid-to-late May in the South. Row covers will keep the pests out, but they will keep pollinators out, too; be sure to remove netting or covers if your crops need to be pollinated. Do not cover plants in bloom that require pollination (i.e., fruits); after the plant sets fruit, then cover it with netting. - Spray Neem oil if early: Deter feeding by adult beetles by spraying plants with Neem oil, which contains potassium bicarbonate. Adult beetles ingest a chemical in the neem oil and pass it on to their eggs, and the resulting larvae die before they become adults. Neem oil is effective for several days, but repeat applications are needed, especially after rainfall. Neem oil is not effective once you have beetles in large numbers. Neem is low risk to bees and other beneficial insects but can be harmful to fish and aquatic life, so don’t use it near lakes, rivers, and water. - Do NOT use traps. They attract beetles, but research has proven that more beetles fly toward the traps than are caught. You’ll be pulling beetles in from all over town and end up with a worse problem. - Choose the right plants: There are some that Japanese Beetles seldom damage, such as boxwood, clematis, chrysanthemum, conifers, daylily, geranium, ginkgo, Japanese tree lilac, forsythia, common lilac, magnolia, red and silver maple, oak, white poplar, redbud, rhododendron, and yew. See our list of the [Best and Worst Plants for Japanese Beetles](. Dispersing the beetle’s favorite plants throughout the landscape, rather than grouping them together, can also help. - Introduce natural enemies: You can also attract native species of parasitic wasps (Tiphia vernalis or T. popilliavora) and flies to your garden, as they are predators of the beetles and can be [beneficial insects](. They will probably attack the larvae, but they are not very effective in reducing the overall beetle population. - Use companion plants: Avoid attracting beetles with [companion planting](. Try planting garlic, rue, or tansy near your affected plants to deter Japanese beetles. (Roses love garlic is a popular expression.) All herbs and other aromatic plants make wonderful companions. Scented geraniums (Pelargonium), rue (Ruta), feverfew (Tanacetum), parsley (Petroselinum), and thyme (Thymus) all may help ward off Japanese beetles as well as [aphids](. Try ornamental and culinary sage (Salvia), anise-hyssop (Agastache), Russian sage (Perovskia), lavender (Lavandula), yarrow (Achillea), oregano (Origanum), catmint (Nepeta) and calamint (Calamintha). Four-o’clocks (Mirabilis) and larkspur (Delphinium) are said to act as decoys by attracting rose-loving Japanese beetles to eat their poisonous leaves, but they do not kill the beetles. - Beware of insecticides: If you wish to use insecticides, speak to your local [cooperative extension]( or garden center about approved insecticides in your area, and be aware of whether you’re killing the very pollinators that bring fruit and flowers! For example, Chlorantraniliprole (Acelepryn®) provides two to four weeks of protection and is low risk to bees. But most dusts or sprays are highly toxic to [honeybees](, [native bees](, and other pollinators. If application of these materials to plants is necessary during the bloom period, do not apply during hours when bees are visiting the flowers (late morning through mid-day). Apply sprays in the morning, never in full sun or at temperatures above 90ºF. If your plants start to wilt, rinse the leaves immediately with clean water. - 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. For rose growers, see our [Growing Guide for Roses]( for more tips on caring for roses! [Japanese beetles] Sometimes the easiest way to get rid of Japanese beetles is to pick them off the plants before they do too much damage. Photo Credit: Jeff Hahn, University of Minnesota. Are you on social? Enjoy more Almanac wit & wisdom! [Facebook]( [Instagram]( [YouTube]( [Pinterest]( [Visit Almanac.com]( [Shop Our Store]( You received this email because you signed for updates from The Old Farmer's Almanac. If you do not wish to receive our regular e-mail newsletter in the future, please [click here to manage preferences](. *Please do not reply to this e-mail* © 2024 Yankee Publishing Inc. An Employee-Owned Company [1121 Main Street | P.O. Box 520 | Dublin, NH 03444]( [Contact Us]( [View web version](