Thursday, August 6, 2009

August Pest of the Month: Japanese Beetles

This June, do you recall seeing the first shiny, flashy metallic copper and green Japanese beetles of the year? When I found one in my garden, it triggered a hazy, unpleasant memory of last year.

Japanese beetles are one of my least favorite signs that summer has arrived. When checking on the green beans a few weeks ago, I discovered DOZENS of them. Next morning,
they were floating in the bird bath and the kiddie pool...and yes, still dozens more dining on our delectable plants.

A while later, as their population increased (and obviously their appetites, too!) they ate
the flesh of the leaves on our green bean plants, reducing each leaf to a delicate, lacy scaffold. When I close my eyes, I can still see images of them piled upon my poor plants.

We often talk about the benefits of planting native species instead invasives. Well, the Japanese beetle is an example of an invasive insect. These pests were accidentally brought to the United States in 1916 (prior to our current agricultural laws). Japanese beetles spread swiftly in our beetle-friendly climate, with an ample food supply, and without their natural predators. Although Japanese beetle populations are only a problem in half of our United States, they are the most widespread turf-grass pest in the United States. At a yearly cost of $460 million.


Once you see adult Japanese beetles, remember that every day each one eats a little more, they mate (piggy back rides on your precious plants...ugh!), then the female burrows down about four inches to lay eggs in your garden or lawn. During an adult lifespan of just two months, females intermittently burrow a few inches into the ground (whether garden or lawn) and lays a few
eggs. She does this until she has "planted" about fifty eggs.

In just two weeks, the eggs hatch into young grubs who begin to feed. Then the larvae (dark brown head, an inch long, grayish-white) wriggle their way up to the roots and other organic matter just under the surface of your garden or lawn. The grubs can kill an area of your lawn, making it able for you to lift a small portion where the roots completely were severed.

In fall, grubs burrow deeper into the ground to overwinter. The inch-long grubs lie cu
rled up in the soil. As the soil warms in spring they push their way upward. In the early spring, grubs return to the surface and continue to feed on roots until they eventually emerge as adult beetles.
Yes, it is the time of year when our yards, and possibly our neighbors' yards, have become havens for Japanese beetles. As gardeners, we have provided them with a delicious variety of new greens to dine on.


These pests are pervasive, so it
's nearly impossible to completely eradicate them from your yard. Since they can fly up to five miles a day, there are always more troops on their way to replace the ones you've trapped or killed. Integrated Pest Management (IPM) is a fancy way to say "hit them from all sides"...combining forces is your best bet
  • Clean Them Up: If you only have a few Japanese beetles, you can try spraying them with a mixture of soap and water.

  • Hand pick them from your plants, pull them off and kill them. As far as Japanese beetles are concerned, the more the merrier; the more you already have, the more you'll get. Pluck the Japanese beetles from your plants and drop them in a container of soapy water, unless you are the type who enjoys squishing them.

    When you remove them from your plants (kill them), you are sending a message to the other beetles that this isn't a safe harbor for them. So, fewer beetles will be attracted to that plant. If you allow the
    m to congregate on your plants, more will join the party. The best times to hand pick them are early morning or late evening when they are less active in the cool morning air.

    For easier handpicking : In the morning spread out a sheet of paper under the infested plant. Shake the plants and the beetles will fall onto the sheet. Slide them into a bucket of soapy water.

  • Turn vacant soil to expose the grubs for the birds (or your chickens) to eat the grubs.

  • Natural repellents include plants (such as Catnip, chives, garlic, tansy and rue) as well as the remains of dead beetles (yuck).

  • We recommend and carry Neem organic insecticide/fungicide as a control for adult beetles and grubs.

  • Plant "trap" crops (evening primrose, soybeans, wild grapes, African marigolds, borage and knotweed) to draw the beetles away from the rest of your garden. Better yet, plant a diversion garden far away and place a trap in it.

  • Beetle Traps are both easy and relatively inexpensive, but they have one major drawback: they attract more beetles than they actually catch (just 75 percent caught). So, should you decide to use traps, place them away from infested plants so you won't attract new beetles. Since Japanese beetles can fly up to five miles, you may be attracting them to your plants from your neighbors' yard.
    ~ Spread traps out as much as you can. Encourage your neighbors to use them, too.
    ~ The lure will get stale over time, replace traps each year.
    ~ The earlier you place the traps, the fewer eggs the females will have laid.
    ~ Place bait traps at least 1 inch off the ground
    ~ Make simple, homemade bait traps in plastic jugs with an entrance hole cut at the top.
    - Choose a sunny spot away from your prized petunias (and other precious plants).
    - The "yuck" factor comes in when you have to strain the bodies out of the traps each night, since the smell of dead beetles is a deterrent.
    - Recipe for Japanese Beetle Trap and Bait: Dissolve ¼ cup sugar and yeast pack in 1 cup of water. Mix a well-mashed banana into the sugar water. Pour this mix into a gallon milk jug. Place the jug (with the top off) in an area where Japanese Beetles gather. The fermentation and odor of the bait attracts the beetles which get in but not out.

  • Place plants that are poisonous to Japanese beetles near your most vulnerable plants (see list of plants desirable to Japanese beetles in the USDA Managing the Japanese Beetle: The Homeowners' Handbook: such as:
    ~ four o'clocks (Mirabilis)
    ~ larkspur
    ~ white geraniums,
    ~ red (and dwarf) buckeyes
    The leaves of the castor bean plant also poison them.
    These plants are poisonous to people to so be careful using them around children or pets.

  • Effective long-term, organic Milky spore (Bacillus popilliae) can be spread over turf to suppress grubs. The larger the area that can be treated, the more effective it is. Enlist your neighbors to follow your lead. Complete control may take a few years. Once it takes effect, one application can last over ten years. The grubs eat the bacterium, and the spores germinate and multiply inside the grub, killing it. As the dead grub disintegrates, the spores re-enter the soil to be eaten by and kill more grubs.

  • Bug "Juice": If you can handle it, this supposedly works well. Harvest about 1 cup of beetles, put them in an old blender and liquefy them. Thin this with enough water to make it pass through a sprayer. Spray it on any plants they victimize.

    Helpful NOTE: If you make this out of beetles infected with the milky spore disease you will actually infect more grubs. So...if you can handle it give it a try!

  • Remember: Pesticides are poisonous! If you use them, always make sure that you follow the instructions carefully. hey also get into the food chain and can pollute water systems. Sprays for adult beetles are often most effective if applied just before or at the start of an infestation. Grub control is best applied in July and early August when small, young grubs are coming to the surface to feed on lawn roots.
Make your yard a less attractive habitat:
  • Remove overripe, rotting, and diseased fruit which attracts Japanese beetles.

  • Diseased trees and plants also attract beetles, then they stay to feed on healthy plants too. Prune and remove diseased plants.

  • Plant species immune to or seldom attacked by Japanese beetles: magnolias, redbuds, red maples, holly or boxwood. Japanese beetles do not like ageratum, arborvitae, begonias, carnations, coreopsis, daisies, dusty-miller, euonymus, hydrangeas, lilies or snapdragons, box elder. Common lilac, Firs, Hemlocks, Hollies, Pines, Rhododendrons, Spruces, Scarlet oak, Tulip tree, White ash, White poplar and Yews.

  • Make your yard and garden less desirable by avoiding growing their favorite plants, such as strawberries and eggplants. (Find a complete list: USDA Managing the Japanese Beetle: The Homeowners' Handbook)

  • Since grubs are not found as often in shaded lawns, plant shade trees and select shade-tolerant grasses for long-term suppression (see URI's Sustainable Tree and Shrub List).
Since the Japanese beetle is such a pervasive problem, it is important for gardeners to use a variety of tools to keep them under control. Whether you hand-pick them, use traps or another method, by reducing your beetle population, you are also preventing more eggs from being laid. If you try a few of these techniques, you are on your way to having your own Integrated Pest Management program.

University of Rhode Island's Fact Sheets on J
apanese Beetles, and White Grubs
USDA Managing the Japanese Beetle: The Homeowners' Handbook

Article by Renee C. Brannigan


Anonymous said...

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Unbelievable...Japanese beetles are one of my least favorite signs that summer has arrived.

Anonymous said...

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