|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.
(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.)
|Beetle grubs are on the cardinal menu|
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.