If you spent your spring picking Japanese beetles off raspberry bushes and flowering plants, this blog post is for you. Because of the life cycle of the Japanese beetle, fall is the best time to prevent springtime infestation of these destructive pests.
In spring and summer, when Japanese beetles are so prevalent and damaging, they mate and lay eggs. Those eggs turn into grubs in the fall, and live underground throughout the winter. And by the time spring rolls around again, the bugs surface and begin to eat plants once again.
So by taking action this fall, you’ll hopefully have less of a Japanese beetle problem come spring. We turned to KARE 11 to learn more.
Maintain a Healthy Lawn
The best year-round tip for preventing a Japanese beetle infestation is to keep the lawn and garden healthy. Remove diseased trees and fruits, both of which can attract the bugs.
Spray with Soap
In the fall when the grubs are nesting underground, spray the lawn with two tablespoons of liquid dish soap diluted in one gallon of water per every 1,000 square feet. This will cause the grubs to surface and will give neighborhood birds some tasty snacks. Repeat every week until you no longer see grubs surface.
Milky Spore or Nematodes
Introducing the fungal disease milky spore will help kill grubs, but it could take time: the spore count must be up for two to three years to be effective. You could also use parasitic nematodes, but this only works when grubs are small and if the lawn is irrigated before and afterward. (If you decide to go this route, we have a variety of lawn aerators available for rent.)
If you know of specific plants that attract Japanese beetles, consider planting garlic, rue or tansy nearby. These are known to deter the bugs.