What Plants Do Japanese Beetles Attack?

One given in the American Gardener’s almanac is that between the months of June and August, a flurry in concern about Japanese beetles descends with them across the country. With their metallic green shells, these rose-loving pests are yet to let up, even with pest control measures in place by countless gardeners, farmers, and horticulturists generally. Although they are one of the rarer pests, adult Japanese beetle damage can be truly devastating. Japenese beetle grubs have been known to defoliate a tree in a matter of days.

As adults, Japanese beetles can feed on around 400 species of plants that grow within gardens in the United States. Trees and shrubs that attract more beetles include ornamental shrubs like roses and a sizeable variety of trees. They also present something of a double whammy in that they feast on different plants as both grubs and beetles.

What Plants Are Japanese Beetles Most Attracted to?

The softer the plant’s flesh, the greatest risk. This, unfortunately, includes fruits and vegetables as the greatest casualties. The leaves preferred by the Japanese beetle include those with softer foliage, especially fruits and flowers which are more delicate to the touch and which they work on in the flesh between the veins.

The most notable victims are roses and hibiscuses and fruits like grapes and raspberries. Vegetables most at risk are soy and maize. Those which will usually survive the brunt of Japanese beetles include the likes of Magnolia (with its tough leaves and flowers) red oaks, pines, red maples, and of course Holly, as well as fruits with a fairly tough skin.

One Interesting Exception

Geraniums, while loved by the Japanese beetle contain a compound that paralyzes them for around half-an-hour and is quite often used as a trap plant by more eco-conscious gardeners who will then collect them one by one and bag them before they are able to wreak any more havoc.

Grub Stage

Japanese Beetles spend 8 months of the year in the grub stage feasting on lawns’ roots. The wetter the grass, the larger the infestation is liable to be.

Although the roots of other plants are not completely immune, it’s the roots of lawns that suffer most during this stage. You’ll know this is the case by a quite severe case of die-back in your lawn which is often so severe that it exposes the topsoil. The positive side of finding Japanese beetle grubs on your lawn at this point is that you can take the opportunity to stop them in their tracks before they develop tougher jaws and mandibles capable of working through your trees’ leaves.

One of the best solutions for curbing further growth is to grab a bag of fertilizer that says “Grub Control” on the label. Apply the grub control fertilizer over the resulting bare patches of grass.

Alternatively, buy a bag of fertilizer that supports nematode growth. It’s these microscopic little creatures’ whose job it is to eat grubs. This is definitely the most environmentally friendly solution as well.

As Beetles

With their small wings, they are not strong fliers, but Japanese Beetles tend to prefer feasting on foliage that grows in sunny areas of the garden. This includes the foliage of mature trees, although larger trees will be able to withstand an invasion of the insects without much long term damage.

The beetles will not touch pine trees and are less apt to attack yews, spruces, or forsythia. At this stage, they tend to seek out softer-leaved maples, oaks (like the tender pin oak), and fruit trees, along with vegetables that range from green beans to soybeans.

One way to swing this to your advantage is to place a pheromone trap at the border of your smallholding or garden. Especially if you can find a suitable trap that doesn’t sabotage other beneficial bugs, this is a great and easy way to check a mass infestation.

For an in-depth List

For a more exhaustive list of the best and worst-faring plants in the midst of a Japanese beetle infestation, you can visit the website for the USDA. If you’re unsure, the tell-tale signs of an invasion of neighboring plants in your area are the best guide.

The Problem With Japanese Beetle Traps

When you first spot Japanese beetles in your yard, you might think that placing Japanese beetle traps would be the most logical next step. However, Japanese beetle traps can in fact make the pest problem worse if they are not used properly. Studies show that these types of pest traps can attract Japanese beetles from more than 5 miles away. If you live in a residential area, this can be a major problem.

Proper Way to Use Japanese Beetle Traps

If you follow the best practices for Japanese beetle traps, then they can be highly effective. To start, avoid placing the traps close to flowering bushes and plants that may attract the Japanese beetles. Experts recommend placing the traps at least 30 feet away from such bushes and plants. Because the trap will fill up rather quickly, it is best to remove beetles from the trap in order for it to remain effective. Failing to remove Japanese beetles as the trap fills up will result in an overflow of beetles that will cause them to find bushes and plants to destroy.

Other Notable Exceptions

Plants in which pungent garlic or onion aroma are usually immune to attack. This is also true of pines.

Farmers have also known for a long time now that some cultivars of fruits are hardier against attack than others, so it’s worth choosing your blackberry variety (for example) more carefully next time you pay a visit to your nursery, especially if Japanese beetles pose a threat in your area.

Here is a further list of vulnerable and less vulnerable plants Japanese beetles attack for the sake of illustration. It should be noted that these beetles will attack even some of the hardier plants on the list for lack of better options though. Click here for more information.

Plants Do Japanese Beetles Attack

Find a reputable local moles & voles pest control Omaha or Lincoln professional that you TRUST and ask about their pest management services. You may think you are saving money however, a single misapplication could have significant and adverse or deadly consequences for you or your loved ones. Contact ABC Termite & Pest Control in Omaha & Lincoln, NE today!

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By ABC Termite & Pest Control | 2022-06-01T14:16:07-05:00 August 12th, 2020 | Japanese Beetles, News | Comments Off on What Plants Do Japanese Beetles Attack?

What Do Japanese Beetles Eat?

When it comes to urban plants and trees, the Japanese beetle is one of the most destructive pests in the United States. It’s no wonder a question commonly asked of pest management professionals is, ‟Will Japanese beetles kill my tree?” It depends. First introduced in New Jersey, this invasive beetle has now spread north to Ontario and Minnesota, west to Arkansas, Iowa and Missouri and south to Alabama and Georgia. The Eastern portion of the United States provides a near perfect climate for this voracious pest. So, what do these beetles look like and what plants do Japanese beetles eat?

Looks can be deceiving.

Both the adult and larval (grub) stages of this beetle cause damage, so it’s important to know what each looks like. The adult Japanese beetle has an attractive appearance – its body is bright metallic green and the wing covers are a copper color. It also has white spots of hair under the wing covers on each side of its body. The adults are small, measuring between one-third and one-half of an inch in length. Grubs are white colored with tan or brown heads. A fully matured grub is approximately 1 inch long.

Lots on the menu.

When asked, ‟What do Japanese beetles eat?” a more appropriate question might be, ‟What don’t they eat?” Adult beetles are known to feed on more than 300 species of plants. To make matters worse, they feed in groups, starting at the top of the plant and working their way down. This ‟group feeding” behavior is what causes the devastation to the plant or tree. Plants that have been injured by the Japanese beetle give off an odor that attracts even more beetles, thus compounding the problem. Japanese beetles are very mobile and can infest new areas from several miles away.

But it doesn’t stop there. Adult female beetles lay eggs in the soil, which hatch into grubs. The grubs feed on the roots of turfgrass and vegetable plants. They especially thrive on the kind of high quality turfgrass found in parks, golf courses and lawns. A common sign of a Japanese beetle infestation in turfgrass is large dead spots that can be rolled up like a carpet because the root system has been destroyed.

Foods of choice.

Japanese beetles are not picky eaters, however, they do have their favorite foods. Roses, sassafras, Norway maple, Japanese maple, black walnut, gray birch, American elm and practically any type of flowering fruit trees such as grape, pear, plum, peach and cherry are all at the top of their ‟favorites” menu.

Assessing the damage.

But that still doesn’t answer the question, ‟Will Japanese beetles kill trees and plants? If the evidence of an infestation is found in the early stages, trees and plants can be saved with the proper care. Removal and control of Japanese beetles is usually best performed by a professional that specializes in lawn care or tree care.

If you have questions about Japanese beetles that are specific to your yard, such as, ‟Do Japanese beetles eat tomato plants?” or ‟Do Japanese beetles eat hostas?” call Terminix® and get advice straight from the experts.

The Story of Japanese Beetles (And How to Fight Them)

The Japanese beetle is a major plant pest in North America, eager to chomp through the leaves of hundreds of ornamental plants, fruit trees and vegetables. These imports from Asia have been in the U.S. for more than a century and are a real bane for many gardeners.

Eradicating them has proven difficult since they live underground as grubs and are only active a short time in the summer.

Is it Really a Japanese Beetle?

Regardless of how much damage they cause, it’s hard not to admire the appearance of Japanese beetles. Their head and thorax are covered in a metallic green shell and their wing coverings – technically called elytra – are a shimmering copper color. Taken together, it’s a striking design courtesy of Mother Nature.

Like all beetles, Japanese beetles have six legs, two antennae and wings. They’re clumsy flyers, often bonking into objects as they travel. Toward their back-end, Japanese beetles sport six tufts of white hair on each side of their body. These tufts are often key to identifying them when comparing them to beetles of similar coloration.

From Japan to the U.S. and Beyond

It shouldn’t surprise you that Japanese beetles are originally from Japan. In their home range, these beetles are minor pests because they have a number of natural predators. Also, the Japanese climate helps to keep them in check.

The insects seem to have entered the U.S. in 1916, where they were stowaways aboard a shipment of irises. From that landing point on the Eastern Seaboard, they began to spread west and north – they are now found in Canada and through much of the U.S. east of the Rockies.

At the same time, these beetles also moved into several other countries, and have strong populations established in Portugal and western Russia. They are also believed to have spread into India and Korea and were recently found in Italy as well.

Scientists believe that their expansion is being facilitated by humans and their love for lush, green lawns that are frequently watered — perfect conditions for Japanese beetle larvae to thrive.

Damage from Adult Japanese Beetles

Japanese beetles are notorious for damaging a wide variety of plants in North America, including roses, vegetable crops, flowering plants and shrubs. They eat the foliage of these plants, always focusing on the tender plant material between the veins of the leaf. This feeding process, called skeletonization, leaves the plants decimated.

At last count, Japanese beetles were known to prey on more than 200 plants in North America. Here are just a few of the well-known plants that are susceptible to Japanese beetles:

• American mountain ash
• Birch
• Common Mallow
• Crape myrtle
• Flowers (Althaea, cardinal flower, clematis, evening primrose, dahlia, gladiolus, hibiscus, hollyhock, morning glory, peony, rose, zinnia)
• Fruit and Berries (Apple, apricot, cherry, crabapple, grape, hawthorn, peach, plum, red raspberry)
• Horse chestnut
• Linden (American, European)
• Maple (Japanese, Norway)
• Pin Oak
• Summer Sweet
• Vegetable (Asparagus, rhubarb, soybean, sunflower, sweet corn
• Virginia Creeper
• Walnut (Black)
• Willow

Damage from Japanese Beetle Grubs

Unfortunately, the damage wrought by Japanese beetles isn’t limited to their adult form. As grubs, these insects bury themselves under your lawn where they do their best to ruin your grass.

After hatching in late summer, the grubs dig into the soil – often up to a foot deep. At this point, they are relatively dormant and stay inactive until the spring. As temperatures warm, the grubs work their way toward the surface again where they feed on the tender roots of turf grasses. As a result of this extensive feeding, these underground feeding machines leave patches of dead grass. Their dining habits destroy roots and reduce the grass’s ability to take up water. This damage causes the grass to die off during hot and dry weather.

You can check to see if Japanese beetle grubs are the culprit to your lawn problems by digging up a damaged section of turf and looking for the curled, c-shaped grubs, which are about 1 inch long. If you find more than 10 per square foot, expect significant damage from these grubs.

Japanese Beetle Control Methods

There are two primary ways to control adult Japanese beetle populations. The first which is probably the easiest and least expensive, is to set up a non-toxic Japanese Beetle Trap near the afflicted foliage. These traps use a pheromone lure to attract male beetles, which interrupts the breeding cycle.

The second option is to use an insect-killing spray that attacks the insects without affecting the plant. Safer® Brand has two sprays available to control these pests. First is Safer® Brand End ALL® Insect Killer, an OMRI Listed® treatment that’s compliant for use in organic gardening. It allows you to use it up to the day of harvest. Also available is Safer® Brand BioNEEM® Insecticide and Repellent, an OMRI Listed® contact killer that doesn’t persist in the environment.

Other methods are also available, but they may require quite a bit more of a hands-on effort.

• Hand-Picking: For one thing, you can try hand-picking the beetles off your plants. This method is effective, but it assumes you have lots of time.
• Domestic Animals: Certain domestic animals are also known to be voracious beetle eaters, including chickens, ducks and guinea hens. Bringing those birds onto your property presents its own challenges though!
• Wild Animals: Many species of wild animals also will eat Japanese beetles. Wild birds known to eat these beetles include robins, cat birds and cardinals. Mammals – namely opossums, raccoons, skunks, moles and shrews — will eat beetle grubs, but you can also expect them to dig up your lawn in the process.
• Parasites: Other options include introducing parasitic organisms to attack the beetles, including nematodes, the milky spore bacterium, certain tachinid flies and tiphia wasps. Though these are natural solutions, they can be purchased at local plant nurseries and released in your yard and garden. Be warned, they may take a while before results are evident.

When feeding, Japanese beetles skeletonize foliage by eating all the green between the veins of a leaf.

The Gardener’s Bane: Japanese Beetles

Are you in a battle with Japanese beetles in your lawn or garden? Let us know if you have any questions by reaching out to us when you visit Safer® Brand on Facebook. You’ll be joining a community dedicated to organic gardening!

You can also subscribe to the Safer® Brand E-Newsletter for more links to articles like this one, special announcements and links to the Safer® Brand products you need!

Japanese beetles in yards and gardens

Japanese beetle infestations in Minnesota are mostly found in the Twin Cities metropolitan area and southeast region of the state.

There are both nonchemical and insecticide options for managing Japanese beetle adults and grubs.

The Minnesota Department of Agriculture monitors this invasive species. Please report Japanese beetles found outside the seven county Twin Cities metropolitan and southeast areas of Minnesota to Arrest the Pest.

Japanese beetles (Popillia japonica) were first found in the United States in 1916, after being accidentally introduced into New Jersey. Until that time, this insect was restricted to Japan where it is not a major pest. This pest is considered to be an invasive species. It is now found throughout the eastern U.S., except for Florida, and continues to move westward.

Japanese beetles were first discovered in Minnesota in 1968. At first, only a few beetles were found. By 2001, they occurred in much higher numbers. In one year the Minnesota Department of Agriculture (MDA) trapped more than one million beetles. Since then, Japanese beetle numbers have fluctuated from year to year.

Japanese beetles are most commonly found in the Twin Cities metropolitan area as well as southeast Minnesota. The MDA maintains an updated distribution map of Japanese beetles.

How to identify Japanese beetles

Adult

• Approximately 1/3 to 1/2 inch long.
• Metallic green head and thorax (the area behind the head) with copper-brown wing covers.
• The sides of the abdomen have five white patches of hair, and the tip of the abdomen has two patches of white hair.

Larva (white grubs)

• C-shaped, white to cream-colored grubs with a distinct tan-colored head.
• Legs are easy to see.
• From 1/8 inch up to about one inch long.
• Japanese beetle grubs look like other white grubs and can only be positively distinguished by examining the pattern of spines and hairs on the underside of the tip of the abdomen.

• Japanese beetle grubs spend the winter underground in the soil of lawns, pastures, and other grassy areas.
• In spring, grubs move up near the soil surface to finish feeding and pupate into adult beetles.
• Adult beetles start to emerge from the ground in late June or early July. They can fly up to several miles to feed.
• Adults feed primarily in July and August, although some may be active into September.
  • Beetle-damaged leaves emit feeding-induced odors that attract other beetles (like sharks to blood).
  • This often results in large clusters of beetles feeding and mating on particular plants while neighboring, equally attractive plants are only lightly infested.
  • Females will lay eggs several different times during July and August, totaling as many as 60 eggs.
  • Dry soil conditions can reduce egg survival, resulting in fewer adult beetles the following year.
  • The eggs hatch in about two weeks and the grubs feed mainly on the roots of lawn grasses.

  

  Damage caused by Japanese beetles

  Japanese beetles are a serious pest of flowers, trees and shrubs, fruits and vegetables, field crops and turf. Adults feed on more than 300 plant species, whereas the grubs feed mainly on the roots of grasses.

  Adult Japanese beetle damage

  Adult Japanese beetles feed on the leaves, flowers and fruits of many different plants. Preferred plants include rose, grape, linden, apple, crabapple, cherry, plum and related trees, birch, elm, raspberry, currant, basil, Virginia creeper, hollyhock, marigold, corn silks and soybean.

  They skeletonize leaves by feeding on tissue between the major veins giving them a lace-like appearance. Damaged leaves turn brown and may fall off.

  Adult Japanese beetle damage usually affects only the appearance of plants.

  Healthy, mature trees and shrubs can tolerate a lot of feeding without significant, long-term injury.

  Japanese beetle grub damage

  Grubs chew grass roots and reduce the ability of grass to take up enough water and nutrients to remain healthy. When grub feeding is severe, dead patches of grass develop.

  These dead patches can be rolled back like a carpet due to the lack of roots. If grubs are not found, examine still living turf at the edges of damaged areas for their presence.

  Healthy turf grass can typically tolerate up to 10 grubs per square foot. Follow recommended lawn care practices to promote a healthy lawn.

  Moles, skunks, crows and other insect-feeding animals may dig up grubs, further damaging the turf.

  White grub damage on lawns

  

  

  

  Managing adult Japanese beetles

  • Japanese beetles can be very abundant in some years and less in others.
  • Japanese beetles are not the end of the world. There are many ways to deal with them.
  • In most cases, Japanese beetle damage is cosmetic only and will not kill plants.

  When to manage: Start early!

  Look for beetles in your yard and garden starting in late June and early July. Start management when they first appear. Damaged leaves attract more beetles so minimizing beetles on plants should mean fewer beetles will be attracted to them.

  Japanese beetles feed for six to eight weeks so it is important to continue management until their numbers decrease. Once they are present in large numbers, managing them becomes more difficult.

  Most feeding is finished by mid to late August.

  Non-chemical management options

  Physical removal

  Physically removing beetles can be a practical and effective management practice for smaller landscapes or a few plants, especially when only small numbers of Japanese beetles are present. Handpick or knock the beetles into a bucket of soapy water to kill them.

  Check your plants daily and remove any beetles that you find to minimize feeding damage. Remember beetle-damaged leaves emit air-borne chemicals that attract more beetles. By physically removing them, you’ll reduce the number of new beetles attracted to your plants.

  The best time to remove Japanese beetles is in the evening or in the morning when beetles on the plants are still cool and sluggish. However, anytime that it can be done is still useful.

  

  Physical barriers

  In some cases, it is possible to protect plants with fine netting to prevent beetle damage. However, do not cover plants in bloom that require pollination (i.e. fruits) as this will prevent pollinators from reaching them. Instead, handpick beetles until the plant is done blooming and starting to set fruit, then cover it.

  Traps

  Don’t use Japanese beetle traps. Hanging a trap in a home garden is not an effective way to protect plants. And they may attract more insects to your yard.

  The traps attract beetles using synthetic female sex pheromone and a blend of chemicals with a strong floral odor. They were developed by researchers to monitor for the presence of Japanese beetles so that management strategies could be implemented.

  While these traps can collect an impressive number of beetles, research at the University of Kentucky has demonstrated that more beetles fly toward the traps than are caught. This usually results in more damage to nearby gardens and landscape plants than would have happened if no traps were present.

  

  Using less preferred plants

  Although Japanese beetles feed on many different kinds of plants, there are some that they seldom damage. When choosing new plants for your landscape, consider using a less preferred plant.

  Plants usually not damaged by Japanese beetles include boxwood, clematis, chrysanthemum, conifers (e.g. arborvitae, spruce, fir, pine), daylily, geranium, ginkgo, Japanese tree lilac, forsythia, common lilac, magnolia, red and silver maple, oak, white poplar, redbud, rhododendron and yew.

  Biological control

  Two natural enemies of Japanese beetles have been released in Minnesota. The fly Istocheta aldrichi lays eggs on adult Japanese beetles in summer, whereas the wasp Tiphia vernalis parasitizes grubs in the spring. Although both natural enemies became established here, neither is very abundant and they have little impact on Japanese beetle populations.

  Is the four o’clock flower toxic to Japanese beetles?

  The four o’clock, also called marvel-of-Peru (Mirabilis jalapa), has been reported by some gardening sites and blogs to not only halt the beetle’s garden invasion but kill them in the process. But these sources offer no evidence of its effectiveness. Four o’clocks are grown as annuals in Minnesota.

  • USDA pamphlets in 1940 and 1963 listed four o’clock as lightly fed by Japanese beetles, but did not mention any toxic effects to the pests.
  • A 2013 Colgate University study did not observe dead beetles when they were only fed four o’clock plants. Some varieties of four o’clock were more heavily fed on than others, however.

  This plant does affect humans. The sap from four o’clocks is a mild irritant, causing itching on the skin. Also, eating the plant may cause stomach upset or other intestinal issues as well.

  If physical removal and barriers are not practical or you wish to supplement non-chemical management, you may choose to use an insecticide to protect valued plants. Remember that insecticides can pose significant risks to beneficial insects, including pollinators, as well as birds, fish and mammals.

  

  Consider using a professional pesticide applicator, especially for trees. See How to hire a tree care professional.

  Use low risk insecticides when they are effective for protecting your plants.

  Low risk insecticides

  Products containing pyrethrins (e.g. Pyola®) are somewhat effective contact insecticides provided they are sprayed directly on the insect. Repeat applications are necessary. Avoid spraying bees and beneficial insects as these products are toxic to these non-pests as well.

  Neem oil is effective for several days but repeat applications are necessary. Neem oil helps deter Japanese beetles but is less effective when large numbers are present. This product is low risk to bees and other beneficial insects.

  Bacillus thuringiensis galleriae (e.g. BeetleGone, BeetleJus), derived from soil bacteria, is moderately effective against Japanese beetle adults, giving one to two week’s protection. This product is not toxic to bees and other beneficial insects. Bacillus thuringiensis galleriae is only available from online sources.

  Residual insecticides

  Several effective, longer lasting insecticides are available for treating Japanese beetles. Chlorantraniliprole (Acelepryn®) provides two to four weeks protection, and is low risk to bees. Pyrethroids, including bifenthrin, cyfluthrin, lambda cyhalothrin, and permethrin, last about two to three weeks. Carbaryl or acephate will provide one to two weeks’ protection

  Caution: pyrethroids, carbaryl, and acephate are toxic to bees and other pollinators.

  Systemic insecticides

  A systemic insecticide is absorbed by the plant and moved through its tissues and is applied as a soil drench or injection, a trunk spray or a trunk injection. This can be useful to avoid pesticide drift, especially when treating large trees.

  Trunk injections should be done by a certified tree care professional.

  Imidacloprid and dinotefuran, both neonicotinoids, are available to residents. They are applied to the soil and only one application is needed per year. Do not apply to soil within 4-5 feet of pollinator attractive plants.

  Caution: Imidacloprid and dinotefuran are very toxic to pollinators. Either avoid applying these insecticides to bee attractive plants or wait until the plants have finished blooming before treating them.

  Professional pesticide applicators have access to chlorantraniliprole (Acelepryn®). This product is long lasting and is a low risk to bees. Professional pesticide applicators can also apply acephate (Lepitech) systemically as a soil drench. Acephate is toxic to bees so applications should not be made near bee attractive plants until after bloom.

  CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Be sure that the plant you wish to treat is listed on the label of the pesticide you intend to use. And observe the number of days between pesticide application and when you can harvest your crop. Remember, the label is the law.

  Managing white grubs

  Controlling Japanese beetle grubs is unlikely to reduce the number of adults on landscape plants. Beetles emerging from non-treated grass areas can fly a considerable distance to preferred adult food plants. Only treat white grubs to protect lawns from damage.

  CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.

  If your lawn has a recent history of grub damage, you may wish to treat with a preventive insecticide in June or early July (see below) to help ensure that the lawn is not damaged again.

  If you adopt a “wait and see” approach, and discover in summer that your lawn has become infested, a curative insecticide can be applied in late July to mid-September when the grubs are still relatively small (1/2 inch or less). Yellowing or browning grass in August is an early symptom of white grub damage. There are other possible causes for discolored turf so check under the grass to make sure it is due to white grubs.

  Once white grubs are nearly full-sized (about 1 inch long), and the turf has begun dying in patches that pull easily from the soil, you can still apply a “rescue” treatment with a fast-acting curative insecticide in September, but expect only partial control. Once the grubs have stopped feeding and started to move downward in late fall, insecticides are not effective against them.

  Do not treat in spring because the large grubs are hard to kill, they feed for a relatively brief time and rarely cause damage in the spring. Treating in spring is no guarantee that the lawn will not be re-infested again in mid-summer.

  Parasitic nematodes, such as Heterorhabditis bacteriophora, are available. They generally do not affect beneficial insects. They need to be applied after the eggs have hatched and the grubs are present. If using nematodes, apply them during cool, overcast days or in the evening and water before and after application as they are susceptible to drying out. While they can be effective, results have been inconsistent.

  Milky spore bacteria, Paenibacillus popilliae (formerly known as Bacillus popilliae) infect only Japanese beetle grubs and have no effect on beneficial organisms. Although these bacteria occur naturally in the soil and may infect a small percentage of the grub population, applying commercial milky spore products has not been shown to provide any benefit in modern university research trials.

  Bacillus thuringiensis galleriae (Btg) is a bacterial strain that produces a toxin that affects beetle adults and larvae. Products containing Btg (grubGONE!®, grubHALT!®) have provided inconsistent (i.e., variable) levels of grub control in recent university trials.

  Preventive insecticides are applied as insurance against grub damage. Preventive treatment may be warranted if a lawn has a recent history of grub infestation, or if the adult beetle flight is particularly high in a given summer.

  The best timing is during the month or so before the adult beetles first emerge and start laying eggs (mid-June to mid-July in Minnesota). Chlorantraniliprole (such as Scott’s Grub-Ex®) is an effective, preventative insecticide that is also low risk for bees.

  Products containing imidacloprid or clothianidin are also effective if applied preventively, but they can pose a hazard to bees foraging on flowering weeds or nesting in treated lawns.

  To minimize their hazard to pollinators

  • Mow any flowering weeds, like clover and dandelions, just before or right after the pesticide application.
  • Avoid areas being used by ground-nesting bees.

  Homeowner products for preventive grub control usually have the words “season-long” grub control on the packaging.

  Curative means treating white grubs when they are feeding and damage is noticed. If turf damage has been sporadic the last few years, it may be worth waiting to see if they are a problem. Watch closely for symptoms of turf damage.

  Effective curative insecticide are trichlorfon, clothianidin, and carbaryl. All three are toxic to bees. Clothianidin, in particular, is systemic; i.e., it can be taken up by the roots and move into the nectar and pollen of flowering lawn weeds.

  To minimize the hazard of curative grub insecticides to pollinators, mow any flowering weeds just before or right after the pesticide application. Avoid areas being used by ground-nesting bees. Homeowner products for curative grub control usually have the words “24-hour” grub control on the packaging.

  Authors: Jeff Hahn, Extension entomologist, Julie Weisenhorn, Extension horticulturist, and Shane Bugeja, Extension educator

  Acknowledgement: Special thanks to Dan Potter, University of Kentucky, for his review and comments on this publication.

  Plants Most Often Damaged by Japanese Beetles

  These plants are favored by adult Japanese beetles and are more susceptible to destruction. Avoid planting them in areas that get regular infestations.

  These plants are least favored by adult Japanese beetles and are less susceptible to destruction. (However, there is no guarantee that these plants won’t be attacked if there are limited food sources in the area!)

  Do you grow roses? See our free Roses Growing Guide for advice on caring for rose shrubs!