Japanese Beetles

Japanese beetles are highly destructive plant pests, causing damage both as adults and grubs. Adult beetles feed voraciously on the foliage and fruit of numerous plant species, including ornamentals, fruit trees, shrubs, vegetables, and field crops. Their feeding habits leave behind skeletonized leaves, damaged flowers, and large, irregular holes in foliage. The beetles begin their life as white grubs in the soil, where they feed on the roots of grass, often resulting in the destruction of lawns.

What do Japanese Beetles Look Like?

Adult Japanese beetles are oval-shaped and approximately 1 cm long. They are metallic green with two bronze wing covers and six white tufts of hair on each side of the abdomen.

Japanese Beetle Life Cycle

During the summer, female beetles intermittently leave their host plants to burrow about three inches into the ground, usually in lawns, to lay a few eggs. This process is repeated until the female has laid between 40 to 60 eggs. By midsummer, the eggs hatch, and the young grubs begin to feed. Each grub grows to about an inch long and curls up in the soil. In late autumn, the grubs burrow 4 to 8 inches deeper into the soil to remain inactive throughout winter. In early spring, the grubs return to the turf and resume feeding on roots until mid-June, when they transform into pupae. Approximately two weeks later, the pupae become adult beetles and emerge from the ground. This life cycle spans one year.

How to Control Japanese Beetles

Japanese beetles have become widespread in our area and appear to be here to stay. So, how can we protect our gardens from these voracious pests? Fortunately, we have some effective options. Spraying adult beetles is not feasible due to the cosmetic pesticide ban, which prohibits insecticides that could effectively target these beetles. The best approach is to keep the beetles off your plants by either physically removing them or luring them into Japanese beetle traps.

Prevention is often the best cure, and controlling Japanese beetle grubs in the soil can be an excellent first step in protecting your plants. The most effective way to control grubs in your lawn is by applying nematodes from mid-August to late September. Treating the grubs reduces the number of adult beetles that emerge in June.

Despite taking measures to control grubs, you might still experience an infestation of Japanese beetles during the summer, as they can fly in from neighbouring properties. Japanese beetles have favourite plants in your garden and tend to cluster together in the evening and early morning. This behaviour makes it easy to gather them up. Simply take a bucket of soapy water and tap the branches with beetles over the bucket. The beetles will fall into the soapy water and drown. Regularly performing this task can limit the damage to your garden.

Another effective option is to place Japanese beetle traps around your garden. These traps use pheromones and floral attractants to lure the beetles in, where they become trapped and unable to escape. For best results, place the traps away from your most valued plants to draw the beetles away. Ideal locations include the perimeter of your property or areas where beetles are less likely to cause damage. Check traps regularly and replace them as needed. Due to the high number of Japanese beetles this year, keeping traps in stock has been challenging. Fortunately, we just received a new shipment, and we currently have two models available.

Protecting your garden from Japanese beetles requires diligence and the right strategies. By combining physical removal, grub control, and the use of traps, you can significantly reduce the impact of these pests on your plants.