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Light colored blooms make beetles sing |
If the invasion hasn’t already hit
your yard, rest assured it will be starting shortly. Those little whispers of
“Tora, Tora, Tora” you may hear while walking through the garden are warnings
that adult Japanese beetles (Popillia japonica) are emerging from the ground, ready to attack more than 300
different species of trees and shrubs, ornamental plants and flowers.
I know because during my last summer in Maryland I went looking for beetles to photograph and didn't see any. Four hours later,
dozens were feasting on some of their favorite victims, my light colored
roses. Blooms of Pristine, Cottage Rose
and First Kiss weren't the only fatalities because before long they were also snacking
on hollyhocks, sweet peppers, Japanese maples and crape myrtles. These eating
machines even like poison ivy.
Japanese beetles were first
discovered in a New Jersey nursery in 1916, possibly having stowed away in a
shipment of iris bulbs. By 1930, the beetles had traveled across almost 6,000
square miles in New Jersey, Pennsylvania and Delaware. Today, the pests are
established in 30 states and continue to spread at a rate of 5-10 miles per
year.
As adult beetles reach the soil
surface, they crawl or fly to low growing plants and begin to feed. The first
ones to break ground release an odor (pheromone) that attracts other adults,
and party time begins in earnest.
The females live about 45 days and
can lay up to 60 eggs each, generally under grass roots in lawns. Within a few
weeks, the eggs will hatch into grubs with voracious appetites. They munch on
grass roots and can devastate a yard. In
fact, according to the University of Florida Extension Service, Japanese
beetles cost the turf and ornamental industry approximately $450 million a
year.
When cold weather settles in, the
grubs move deeper in the soil. In spring, they again feed on grass roots until
pupation in late May. The adults emerge with brilliant metallic green bodies
and hard, copper-colored wing covers to start the assault all over again.
So do we just raise the white flag
and watch our favorite summer plants fight a losing battle? In their homeland,
native predators keep beetle numbers in check.
Not so in America. Adult beetles have few enemies -- they aren’t tasty
fare for birds although grackles, starlings, cardinals, redwing blackbirds and
robins do feed on grubs.
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Beetle grubs are on the cardinal menu |
(My good rose judging friend Jim Diggs tells me sparrows take care of his beetle population in Richmond, VA. He reports the birds knock them to the ground, then lap them up. I had a word with my sparrows who were falling down on the job but they did not respond.)
As a natural control, picking
beetles by hand is safe but not very effective. Shake them into a pail of soapy
water and they’ll eventually drown.
Don’t ever crush a beetle -- as a dying insult
it will release more pheromone and attract even more pests.
Milky spore is a bacterial disease
harmless to humans and animals that kills grubs. It is applied to the grassy areas of the yard
and may take two to three years to become effective. Neem oil, insecticidal
soaps and sprays containing garlic are also recommended. High value plants can
be protected with spun polyester covers such as Reemay.
In recent years, commercial traps have been offered
up as an effective way to thwart the beetle population. Research
done at the University of Kentucky shows commercial traps may attract more
beetles than are actually caught. If you are determined to use traps,
place them at least 30 yards away from plants you want to protect. (In fact, the best idea is to locate the trap in your neighbor's yard.) (:
If you choose to bring out the heavy artillery, keep in mind Sevin kills beneficial insects and other chemicals must
be used with care in areas frequented by children, pets and wildlife.
I tried to avoid the scorched earth
theory of bug control and used a combination of spot pruning and insecticidal
soap to limit the damage. I’ve also heard beetles can be confused by the scents
of garlic, mint, chives, catmint, basil and onions.
These companion plantings
can’t hurt, and certainly might help in our struggle to bid sayonara to a
determined enemy.