By Paul Schnare
I try to listen to gardeners in the area about the time to write when it's my next column. Their concerns are the subjects I think I should write about. With that said, Japanese beetles and their control seem to be on the mind of several gardeners that I have talked with over the last few weeks.
Even though I have written about Japanese beetles before, I think a refresher column might be appropriate.
Japanese beetles were introduced into the United States in New York Harbor in the early 1900s. Since that time, their population has expanded and moved westward. They arrived in our area about 10 years ago.
My first experience with them was when one of my employees brought a few in for us to identify. She lives in the Brewer area and found them devouring some of the flowers and shrubs in her landscape.
In order to understand how to control these insects, it is important to know their life cycle.
The beetles overwinter in soil in the form of grubs. These grubs change into adults sometime in late April and May. The adults fly around landscapes in search of plant leaves and flowers to eat. Quite often they can be found in swarms. I have had them swarm me as I walked outside several times. I keep telling my wife I must really be sweet because they seem to like me so much.
The adults have two things on their mind -- eating and breeding.
After breeding, they lay eggs in surrounding soils, which hatch into grubs. These grubs are also hungry, so they eat plant tissues, mainly roots. If the population of the beetle is large enough, extensive damage can result from the adults eating plant flowers and leaves, while the grubs can cause extensive damage to plant roots. This double whammy can give you an idea of how extensive the damage can be.
In order to control these insects in your landscape, start by applying fertilizers to azaleas, roses and other flowering plants that contain a granular systemic insecticide. This systemic insecticide will be introduced into plant roots, then migrate into the leaves and flowers of landscape plants. When the beetles munch on the landscape plants, they will ingest the insecticide and meet their demise.
A word of caution: Only use the systemic insecticide around non-edible plants in your landscape.
Even if all of the adults are killed, they may have laid eggs in the soil in lawn and landscape beds. These eggs will hatch around August, and the hungry grubs will start munching on lawn and landscape plant roots.
I would suggest an application of a granular systemic insecticide to these soils around Memorial Day, which will last a whole growing season. As the grubs move around in the soil, they will either absorb or ingest the insecticide and meet their demise.
For Japanese beetle control, apply insecticide/fertilizer each spring along with the summer grub-control application. If you don't, next year your landscape may be infested again with adults and grubs that have migrated from your neighbor's yard.
Unfortunately, I think Japanese beetle control will be an annual effort for years to come.
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