It’s that time again, time for Japanese beetles to wreak havoc in the garden.
These metallic green beetles with copper-colored wings and white tufts of hair along their sides spend about ten months of the year in the ground as grubs, feeding on the roots of turf grass and other plants. During their coming out party, they spend their time mating, laying eggs, and feeding on plants.
When Japanese beetles find plants to eat, they send out pheromones to signal other beetles where the food is, and just like a teenager’s party when his parents are out of town, the beetle bash grows larger and larger.
Females continue a cycle of feeding on plants, mating, and laying eggs in the soil among grass roots until September. They can lay as many 50 eggs in a season.
It takes approximately two weeks for grubs to hatch depending on the soil temperature. They move up in the soil and begin feeding on roots and other organic matter until cold temperatures trigger them to descend deep into the ground for winter.
When the soil warms in spring, they head back toward the surface. In late June, they emerge again as another generation of Japanese beetles.
Japanese beetles can cause considerable damage to plants, trees and shrubs in their short stint out of the soil. They eat holes in flowers.
They skeletonize leaves.
Although the damage appears dreadful, Japanese beetles rarely kill plants. If control is deemed necessary, choose a method as safe to other pollinators as possible. Here are some of the safest options.
Hand pick. The most effective and safest way to control Japanese beetles is to pick them off and drop them into a container of soapy water. Japanese beetles move slow and when agitated, they fold their legs and drop, so it is pretty easy to knock them to their death in the soapy water.
Apply Milky Spore. Milky Spore is a bacterium that attacks grubs. Grubs must be present in the soil for the bacterium population to build high enough to be effective. Experts also remind us Japanese beetles can fly a mile or more in a single flight. You could rid your yard of grubs and the beetles might glide on over from your neighbor’s property!
Use insecticidal soap. Insecticidal soap kills Japanese beetles on contact. It has no residual effect – if beetles escape the pesticide shower, they are unharmed.
Use pyrethrin or neem oil. Both of these sprays kill Japanese beetles on contact and have some residual effect.
Whether insecticidal soap, pyrethin or neem oil is your chosen method, do not apply when bees are active and always follow labelled directions.
Do not use traps. Japanese beetle traps use pheromones to attract beetles. Why would you want to attract them? Aren’t you trying to get rid of them? Traps attract more beetles than they can catch.
Sometimes, gardeners have to wage war on garden enemies. I am heading out to battle with my Japanese beetles. My weapons of choice are my fingers and can of soapy water. What are your preferred munitions? Share your victories and defeats. Garden with me!