JAPANESE BEETLE
Popillia japonica

Name and Family

Japanese Beetle, Popillia japonica, is a member of the scarab family (Scarabaeidae).

History

  • The first Japanese beetle found in the US was found in 1916. 
  • It is believed that the beetle was transported within a shipment of iris bulbs. 
  • The first Japanese beetle found in Canada was found in 1939, in a tourist’s car after arriving in Yarmouth, NS by ferry from Maine.
  • It was first found on PEI in 2009 in a campground between Charlottetown and Cornwall.
  • Japanese beetle is mainly found in the capital region of PEI, including Charlottetown, Stratford, Cornwall, West River, and Winsloe.
    • The PEIISC is very interested in tracking the spread of this beetle. We are especially concerned with sightings of Japanese beetles from outside this area, but reports from within the areas listed are valuable information too.

Identification Guide

Here are some distinguishing features of the adult Japanese beetle that may help positively identify it:

Adults

  • Approximately 15mm long and 10mm wide.
  • Iridescent, copper-colored forewings.
  • Green thorax and head.
  • Japanese beetles are clumsy flier.
  • Has tufts of white hair bordering its abdomen.
  • Adults appear in summer, emerging from the soil in late June-July.
  • Peak adult beetle populations are present in July-August, and after that, they gradually disappear.

Larvae

  • The C-shaped larva (grub) is a creamy-white colour with a yellowish-brown head. 
  • Larvae look very similar to those of the June bug, but are smaller and have a distinctive pattern of hairs at their posterior.
  • Larvae are found from late summer to June.
  • Larvae feed on the roots of turf grasses, which can then be pulled up just like a carpet.
  • Damage appears as dead grass, and larvae are usually found near the edges of these patches of dead grass.
  • This is the overwintering stage.

Eggs

  • The least noticeable life stage.
  • Laid underground near the roots of turf grasses.
  • Eggs look like miniscule chicken eggs, about the size of a pinhead.
  • Eggs hatch after two weeks.

What it does in the ecosystem

  • The adult beetle feed on over 300 species of plants, skeletonizing the leaves (eating the green, leafy material and leaving behind only the leaf veins). 
  • The larvae feed on the roots of turf grass and other plants and can seriously damage lawns, sports fields, golf courses, and turf production.
  • Between the above-ground feeding of the adult beetles and the below-ground feeding of the larvae, the Japanese beetle can significantly damage landscape plants, ornamental plants, fruit and vegetable gardens, nurseries, orchards, and agricultural crops. 
  • When they become very numerous, Japanese beetle can have a significant impact on native species as well.
  • The beetle is known to affect: elm, maple, grape vines, hops, canna, crape myrtles, peach, apple, apricot, cherry, plum, rose, zinnia, corn, asparagus, soybean, blueberries, raspberries, blackberries, and others.

Management

GENERAL CONSIDERATIONS

Managing a Japanese beetle infestation is a challenging process, but diligence and careful planning may eventually get the population under control. Often, multiple control methods are used simultaneously. If you are in an area with known Japanese beetle presence (mainly Stratford, Charlottetown, or Cornwall on PEI) Regularly check on the plants on your property for signs of Japanese Beetle damage to nip the infestation in the bud.

Before selecting a control method, consider: 

  • The size of the infestation. 
  • Resource availability. 
  • The amount of effort you are willing and/or able to expend. 
  • Tthe local ecosystem and what other organisms or ecological processes may be affected by your management. 
  • Japanese beetles have generalist feeding behaviour, and can almost always find a host plant. Management may be frustrated by new arrivals to the area that fly in from your neighbour’s yard, the nearby woods or meadow, or anywhere else a suitable host may be found.

LIFE CYCLE

  • This beetle is harmful both in its adult and larval form. 
  • Adults feed on the foliage of hundreds of species, and the larvae (also called grubs) feed heavily on the roots of grasses and various other species
    • Larvae can cause serious damage to turf grasses. 
  • During the adult feeding period, female beetles will feed and then periodically dig into the soil about 3 inches deep to lay eggs, repeating this process until she has laid 40 or so eggs. 
  • The eggs hatch in mid-summer and turn into white, c-shaped larvae. This is when they begin to feed on the roots of grassesand other plants. 
  • In autumn these larvae burrow 10-20cm into the soil to overwinter. They are inactive through this season. 
  • In the early spring the larvae move upward in the soil to feed on shallow roots (like those of turf grasses) until the late spring when they turn into pupae. These pupae persist for 2 weeks before the adults emerge (approximately June – July). 
  • As adults, they live 30-45 days. 

Before deciding which management practice to choose, it is important to consider what time of year you plan to undertake the management. Knowing when beetles and larvae are present and active will help you select the best control tactic for the given time of year.

CONTROL TACTICS, PREVENTATIVE

Start thinking about Japanese beetles in the early spring when you are purchasing new plants for your property. 

  • There are many species that are resistant to the beetles: red maple, ash, lilac, spruce, pine, columbine, begonias, and more.
  • Adults are especially attracted to roses and grapes, so if you have noticed the beetles targeting a specific species in the past, you may want to consider replacing it with something less attractive to them.
  • To protect the foliage of existing plants, you can place netting material over them in early spring to prevent feeding. The beetles are attracted to damaged plants, so consider covering any ornamental plants that may be in poor health. 

CONTROL TACTICS, ESTABLISHED POPULATIONS

Once adults have emerged (mid-June to mid-August), the simplest method to control small to medium-sized Japanese beetle outbreaks is to hand-pick the beetles and put them in a container of soapy water. 

  • If this is done on a consistent basis you should notice a decline in the number of beetles you have to manage on a day to day basis. 
  • Try to get the on your first grab, as the beetles tend to drop off and fall when disturbed. They can easily get lost in the grass or surrounding vegetation.
  • Grab a coffee and get out early as the best time to do this is in the morning!
  • Japanese beetles are least active in the morning and are easier to catch (this applies to dark or cloudy days too). 
  • The beetles tend to move to the top of the plant in the early morning, just before the sun rises. They are easy to spot at this time.
  • Repeating this tactic daily is ideal. 
  • Their daily feeding will cause damaged plants to release compounds that will attract more beetles to the area, so getting them before they begin daily feeding is helpful for this reason as well. 
  • Don’t smash beetles, as this will release pheromones that attract other Japanese beetles.
  • You can expedite the picking process by using a handheld vacuum cleaner to suck the beeltes up.

Another option for management is placing pheromone traps nearby, but this management tactic is controversial. 

  • Traps use a chemical attractant to lure Japanese beetles. This attractant may attract additional Japanese beetles to the area and increase the damage to host plants that are nearby the trap. 
  • While ultimately you will be removing Japanese beetles from the general area, you will potentially increase the number of beetles present nearby the traps. 
  • Only 75% of beetles that are attracted to the traps will actually be trapped, meaning this is not an effective method for complete eradication. 
  • There are many different options for traps, but “bucket traps” seem to be a favorite among professionals. 
  • Place traps away from any plants you would like to protect. For maximum yield, place the traps near a favourite plant eaten by Japanese beetles. Place the traps in early June, when adults begin to emerge, and replace them at least annually. If you live in an infested area, you will probably need to empty the traps often. Dump the traps into a bucket of soapy water to drown the beetles. For the management of large outbreaks, traps are considered ineffective. 

Moist soil is essential for egg laying and hatching. Disrupting soil-borne eggs and larvae is a great way to control the beetles at another life stage.

  • Eggs are laid in the soil, and larvae spend their early life there. 
  • Don’t water your plants as often when they are affected by Japanese beetles, as the beetles need a moist environment to reproduce. 
  • Rototilling an affected area also helps to reduce the survival chances of the soil-borne larvae. Till during hot and dry conditions, as eggs and larvae are sensitive to dessication. 
  • Unfortunately, these methods themselves can be damaging to your plants. 

BIOLOGICAL CONTROL

Several distinct biological controls for Japanese beetles are effective in their treatment. 

  • You must ensure that any of control measures selected are approved for use in your area. It is important that these controls be applied with care and expertise. This is because all biological controls involve the release of an exotic species that, though intended to act specifically on Japanese Beetles, may have unintended ecological consequences. 
  • These controls are also more difficult to apply correctly, so professional application will likely increase efficacy. Available controls include nematodes, parasitic wasps & flies, and bacterial toxins. 

Nematodes are tiny wormlike creatures. The nematode species Heterorhabditis bacteriophora is a commercially available variety used in the control of scarab beetles. 

  • The nematode has a beneficial relationship with a bacteria. 
  • When the nematode penetrates Japanese beetle larvae, it becomes infected with the bacteria, which feeds on the larvae’s flesh. 
  • The nematode eats the bacteria and uses the larvae as a host for its reproduction. Eventually, these processes will kill the affected larvae. Nematodes are applied using a sprayer, much like an insecticide. 

Two species of parasitic insects with a specific host preference for Japanese beetle have been found to be able to establish populations in North America. 

  • These have been released after periods of extensive research by professionals under the supervision and guidance of federal regulatory agencies. 
  • They have proven effective in reducing Japanese beetle populations where established. 
  • Tiphia vernalis is a wasp that parasitizes Japanese beetle larvae.
  • Istocheta aldrichi is a fly that parasitizes Japanese beetle adults. 
  • Neither species is available to the public or commercially. 

A final method of biological control is the use of bacterial controls, namely Milky Spores and Bt toxin. 

  • Milky Spores are those of the bacteria Bacillus popilliae, which is ingested by larvae.
    • The bacteria use Japanese beetle larvae as a host, killing them and releasing millions of additional spores into the area after their death. 
    • This means that Milky Spore treatment becomes more effective overtime and is proven to eradicate large populations of Japanese beetles. 
    • Application is similar to traditional insecticides.
  • Bt toxin is even more effective and has a similar mode of action to Milky Spores.
    • The bacteria Bacillus thuringiensis (Bt) is a applied as a microbial insecticide. 
    • The bacteria are consumed by the larvae. 
    • The toxins secreted by the bacteria act as a gut poison and kill the larvae.
    • Applied much like traditional insecticides. 
  • The drawback of soil applied products is that the larvae, even though they prefer turf roots, can be anywhere in your yard – turf, garden, woods, meadow etc. Applying it effectively can be difficult due to the area of application needed.

CHEMICAL CONTROL

Chemical control methods exist for the treatment of Japanese beetle, but the PEIISC does not offer advice on chemical control measures at this time. 

  • As Japanese beetles have a diverse range of hosts, chemical treatment may be ineffective in eradicating all beetles in an area. 
  • The population hosted by a neighbouring tree that you didn’t treat might repopulate treated areas the following season. 
  • If using chemical controls, it is imperative that all local legislation and manufacturer’s instructions be followed during application.

Whatever treatment method you select, it is important to regularly monitor the site after treatment to ensure that a resurgence of Japanese beetles does not occur. Stubbornness and diligence are key in the fight against this invasive species.

Dispose of beetles in a sealed clear bag in your waste bin. When disposing of beetle, be sure that they are all dead! If not a risk of spread during waste transit and processing exists. 

FOLLOW-UP AND DISPOSAL

  • Whatever treatment method you select, it is important to regularly monitor the site after treatment to ensure that a resurgence of Japanese beetles does not occur. 
  • Stubbornness and diligence are key in the fight against this invasive species.
  • Dispose of beetles in a sealed clear bag in your waste bin. 
  • When disposing of beetle, be sure that they are all dead! If not a risk of spread during waste transit and processing exists.

Map

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References

Japanese Beetle (Coleoptera: Scarabaeidae) Invasion of North America: History, Ecology, and Management | Journal of Integrated Pest Management | Oxford Academic (oup.com)

USDA Japanese Beetle Homeowner’s Manual (maine.gov)

USDA APHIS | Japanese Beetle

Japanese Beetles in Nursery and Turf (gov.on.ca)

Japanese beetle – Integrated Pest Management (msu.edu)