How To Control Japanese Beetle

Identifying Japanese Beetles

They are a pest that is sweeping across neighbourhoods, devastating gardens, shrubs, trees and field crops without mercy. Originating from Japan, the Japanese Beetle landed in North America unintentionally around 1916… over a century ago, so at this point they’re likely here to stay. While they are naturally controlled in Japan, the lack of enough natural predators here has made them a major pest. Japanese Beetles are especially attracted to plants like raspberry, canna, roses, potato vine and maples among many others. They’ve been known to feast on over 300 plant spices (so unfortunately it’s not a selective eater).

Japanese beetles are an easy pest to identify in the garden as they make themselves known immediately. When present you can spot them as they have bright metallic green heads with metallic copper-coloured bodies. If none are visible, the skeletonizing of the leaves they feed on is a dead giveaway. These beetles seem to not enjoy the veins as they feed around them leaving the distinct damage in their wake.

This frustrating insect is a hard one to control for a couple of reasons, first is a lack of ‘quick and easy’ options to apply and the second is the physical structure of beetle pests. Their hard shell is thick and provides protection from traditional options that can penetrate thinner pest coatings. That said there are still things that gardeners can do to fight these nasty bugs and thwart their effect to destroy your beautiful gardens!

Mechanical Control: Old Fashioned Hand Plucking

Although it’s often the least preferred method for busy (or queasy!) gardeners, picking newly arrived beetles manually off your plants and disposing of them can be a great preventative measure. Where there is one today, there will be more tomorrow! Preventing them from settling in can help you in your battle.

• Grab a pair of gloves if you’d like, and a bucket filled with soapy water.
• Handpick or shake the bugs into the bucket where they will drown. You can leave the dead beetles beside your plant to scare off any future munchers.
• Japanese beetles are sluggish and sleepy in the early morning and their iron-like grips are often very relaxed making them easy to shake off. They are also less likely to take flight when shaken off in the early morning and more likely to land in your soapy water.

Biological Control: Nematodes

Nematodes can help in the two-pronged attack of Japanese beetle prevention. Applying nematodes in the spring and fall when they live in your soil closer to the surface as grubs can kill the problem before they emerge as adult beetles.

Only the nematode heterorhabditis bacteriophora is effective in Japanese beetle grub control. Don’t worry, that’s the kind in those red packages of Lawn Guardian nematodes that we sell at Heeman’s.

This is not to be confused with other types of nematodes (Yes! There are actually many different varieties just like in say… dogs or fish!) so getting the right one is key as nematodes are reared for attacking specific grubs or pests.

Important to mention that nematodes are great at controlling the grub stages in your lawn but should be used in conjuction with other control methods. Those winged pests can just fly in from other yards so a multi-pronged approach (or a neighbourhood pact that everyone applies nematodes!) is best.

Biological Control: Birds & Other Predators

Planning a garden that is biologically diverse, and a friendly environment for birds can help with natural predation of the beetles. Starlings (as much as they are sometimes an issue on their own) are known to love both the adult and larvae stage of Japanese Beetles. Other birds like the crow, blue jay, cardinal, sparrow, duck, wild turkey and robin all feed on the grub stage, and sometimes the adult beetles!

To create an inviting environment, think about adding native plants, a year-round water source, leaving some (tidy!) brush piles or dead trees, putting up and properly maintaining nesting boxes, and reducing the use of insecticides (they’ll need those bugs to feed their babies!). Check out our garden guide on Attracting Birds to Your Garden for more tips on creating a bird oasis!

Chemical Controls: Japanese Beetle Traps

These traps use pheromones to attract the insects, and a sack to catch them when they clumsily fly into the trap (they’re notoriously poor flyers). They’re proven to be highly effective in attracting the beetles (but maybe too much so?).

Studies have shown that the traps can often attract more beetles than they can actually trap, which is why these are not our first recommendation… it sometimes mean more beetles than what you started with! So if you’re going to use traps, we recommend:

• If you have a large yard, place the traps FAR away from your garden or ‘hot spots’ to draw the beetles away from your treasured plants. Unfriendly neighbour’s yards (kidding! sort of) or a far away corner or end of your property make great homes for your traps.
• Empty the traps as soon as they start to get full, sometimes multiple times a day if you have a big infestation. The number of beetles some traps can hold can be as little as only 10-15.
• If you have a smaller yard, you can try putting the trap out for a day or two at a time every couple of weeks.

Chemical Controls: Pyrethrum Based Products

Most pyrethrum based products (like EndAll for example) will work on Japanese Beetles but pyrethrin insecticide should still be applied selectively and directly on the beetles, since it will also kill other insects.

Pyrethrin is a biodegradable substance derived from chrysanthemums and it has no residual effect on the environment, making it one of the safest pesticides you can use (but please use all chemical controls carefully, only when needed and follow all directions carefully).

Prevention

Japanese beetles are known to feed on many plant species, but sometimes avoiding their favourites can help keep them away. If you have major problems with Japanese beetles or have a serious phobia, avoid plants like roses, Japanese maple, raspberries and cannas. We have compiled a list of some plants you can use that are less attractive to Japanese beetles, which you can find in our Garden Guides section.

Geraniums to Paralyze Japanese Beetle?

Research out of Ohio State University shows that geranium flower petals have toxic effects on Japanese beetle. Local gardener Marsha D. brought this to our attention after she decided to do some research when she noticed a large number of dead beetles under her geraniums. Could be some promising developments there, read the full story.

Parting Words

As always, you could also just tolerate them if the damage wasn’t too extreme. Rarely does some defoliation kill previously healthy and established plants, but we agree it does look sad. Japanese beetle activity usually peaks in July and August, so have your plans in place so once you see the pesky (but pretty) scarabs you can be ready to pounce! We wish you the best of luck in your battles!

As always, if you have any questions or need some additional help, come and visit us at the greenhouse! Our friendly Daymakers are around and eager to help.