Japanese Beetle Control

Japanese beetles love hibiscus!

You might think it is a little early to mention Japanese beetles but if you have plants in your garden that attract the little blighters you need to start planning your beetle strategy. I always say you need a multi pronged approach to beetle control and it helps to understand their life cycle to know which control to use when.



The Japanese beetle emerges from the ground in late June or early July and feeds voraciously on your roses, shrubs, trees and whatever else it can sink its little mandibles into and then they lay eggs in the soil. When the eggs hatch they are called grubs and they then feed voraciously on the roots of your grass. As summer turns to fall, they begin to migrate deeper into the soil to over winter. In the spring they move back to feed and then pupate. At this point they are not feeding, but turning into the beetle that emerges to start the cycle all over again. The upshot is you have two opportunities to kill them– in the grub stage and then as adults– and there are several types of controls available at each stage.



In the grub stage you can use a granular systemic insecticide that you apply and then water in. The grass roots take up the chemical (imidacloprid) and when the grub takes a bite– it dies. If you want an organic control you can use Milky Spore, which is a bacteria that kills the grub. It is available in a concentrated powder that you only have to apply once or a less concentrated granular form that needs to be applied six times over two years in order to build up an effective population of bacteria.



Japanese beetles feeding on leaves



Even if you can control the grubs in your own yard, Japanese beetles can fly several miles to find a mate and to feed, so you will still need to control the beetles at the adult stage. You can spray with Eight® or Sevin®, but they will need to be reapplied every 10-14 days. Or you can use a systemic drench. This is particularly effective if you have large trees that are hard to spray. It is a concentrate that you mix in water and then pour at the base of the tree or shrub. The roots take up the chemical (imidacloprid) and move it up to the leaves at about 4-6 feet a week, depending on growing conditions. The protection last 12 months. If you use it on roses, be aware that the chemical does not go into the flowers, so you will still have to use a contact spray on them.



Japanese Beetle Life Cycle