I recently moved to a Plant Hardiness Zone 6 and unlike my previous Zone 5, Japanese Beetles are
everywhere. My neighbour regularly plucks them off her rosebushes and, wanting to avoid
pesticides, asked me what else she can do. This little green and coppery-red beetle is all over
warmer parts of Canada and the US. CFIA has protocols in place in Vancouver for handling
Japanese Beetle infestations without spreading them. In light of this, I thought I would share some
findings on how to control, or at least limit the spread of, the Japanese Beetle.
Japanese Beetles feast on the flowers and leaves of over 300 plants and trees. Not only that, a
female will lay approximately 50 eggs at a time, making it easy for numbers to get out of control.
Like all beetles they go through the egg, larvae (grub), pupae, adult life cycle. Fortunately, they are
susceptible to cultural, biological, and chemical defenses at different stages.
In the grub stage:
Milky Spore attacks the white grubs of the Japanese Beetle before it can develop into an adult, this
takes a couple of years to work, but will last for 10 years.
Nematodes are beneficial against the Japanese Beetle with the most effective species being
Heterorhabditis bacteriophora (commercially available as Heteromask, NemaSeek or Terranem).
Starlings are the biggest aerial predator of Japanese beetle and will enjoy them as grubs or adults
Chemical: Mix 2 tbsp dishwashing soap diluted in 1 ga of water and spread of 1000 sq ft. This will
force the grubs to the surface of the soil where predators will pick them up (choose soaps
made from animal or vegetable oils in accordance with the SOUL Standard).
In the adult stage:
Cultural: Knock the beetles into a bucket of soapy water, the soap will prevent them from flying
away and they will eventually drown.
Chemical: Neem oil (the SOUL Standard allows neem oil when registered for use in Canada)
Remember, pesky insects like the Japanese Beetle can be a sign that something isn’t right the
garden. Be sure to address overall soil and plant health and keep soil microbes happy.
Japanese Beetles also love turf grass, opting for real grass over turf may go a long way.
For more information on Japanese Beetle and how to combat it, check out the sources below.
Master Gardeners of Hamilton County, TN
Planet Natural Research Centre
Gardeners Supply Company