japanese beetle

Japanese Beetles: They’re Back!

Japanese Beetles: They’re back!

Japanese beetles are destructive plant pests both as adults and grubs (larval stage). Adults feed on the foliage and fruit of several hundred plant species, including ornamentals, fruit trees, shrubs, vegetables and field crops. Adults leave behind skeletonized leaves and flowers and large, irregular holes in leaves. The beetle starts out as a white grub in the soil, where it feeds on the roots of grass, often destroying lawns.

Japanese Beetle Life Cycle: During the summer feeding period, females intermittently leave plants, burrow about 3 inches into the ground—usually into lawns—and lay a few eggs.  This cycle is repeated until the female lays 40 to 60 eggs.  By midsummer, the eggs hatch, and the young grubs begin to feed. Each grub is about an inch long when fully grown and lies in a curled position. In late autumn, the grubs burrow 4 to 8 inches into the soil and remain inactive all winter. In early spring, the grubs return to the turf and continue to feed on roots until mid-June, when they change into pupae. In about 2 weeks, the pupae become adult beetles and emerge from the ground. This life cycle takes a year.

Control: Japanese beetles have become widespread in our area and it looks like they’re here to stay.  So how do we protect our gardens from these voracious bugs?  Fortunately we have some options. Spraying the adult beetles is not one of them.  With the cosmetic pesticide ban, insecticides that would be effective on the beetles have now been banned.  Your best option now is to keep the bugs off your plants by either physically removing them or luring them into a Japanese beetle trap.

If an ounce of prevention is worth a pound of cure than controlling the Japanese beetle grubs in the soil might be a good first step to keeping these bugs off your plants.  The best way to control grubs in the lawn is with an application of nematodes in mid- August to late September.  Treating the grubs will reduce the number of beetles come June.

Even if you take care of your grubs you still may have an infestation of Japanese beetles come summer since they can fly in from neighbouring properties.  You will notice Japanese beetles have their favourite plants in your garden and that they tend to cluster together in the evening and early morning.  This behavior makes it easy to gather them up.  Simply take a bucket with some soapy water and by taping the branch with the bugs on it over the bucket will cause the beetles to fall off into the soap-water.  If you do this on a regular basis you can limit damage to your garden. 

The other option is to place Japanese beetle traps around the garden.  These traps are very effective in luring the beetles in with the use of pheromones and floral attractants.  Once the beetles get caught in the trap they are unable to get out.  With so many Japanese beetles this year, we have had a very difficult time keeping traps on the shelf.  At the time of writing we just received a new shipment.  At the moment we have two makes available.

Back to Garden Centre Articles