These horrible and hardy, pests plague gardens, nurseries and orchards from June to September, devouring plants from the top-down. Here are some products and methods to help control these critters:
(Please be sure to always follow manufacturer guidelines when applying/using products.)
Use Insecticidal Soaps! These soaps already come prepared, and contain insecticidal ingredients which will both help to kill these little monsters, and make the sprayed plants less hospitable.
Sprinkle this powder on the leaves/flowers of vulnerable plants to irritate the legs/mouths of the beetles, causing them to leave before they can damage the plant too much. Due to the nature of the powder, it could lead to the death of some of the pests as well. Since this powder has to remain on the plant in order to do its thing, it will need to be reapplied after it rains, or if there’s heavy wind.
Most commercial beetle traps focus on mimicking the pheromones that female beetles give off. Attracted beetles will fly in to the trap, and will be unable to fly out. Remember to place trap as far as possible from plants you want to protect.
Bring a bucket, or container filled with water and a bit of dish-soap and brush any offending beetles off of your plants, and into the soapy water. The soap breaks up the water tension, and drowns the beetles.
Blankets and Tarps:
These critters are most active in the morning, so before evening hits, put blankets over any vulnerable plants. In the morning, the beetles collect themselves on the blankets (they will smell the plants, but shouldn’t be bright enough to realize that they must get under the blankets). Roll up said blankets, beetles and all, and then shake/brush them off into a bucket of soapy water.
For high-target plants like roses and their flowers, beetles will be incredibly tenacious. Oftentimes it is better to nip the buds/flowers off and spray the leaves/stems, and allow the plants to bloom later on in the season when the beetles are less active.
TO REDUCE FUTURE GENERATIONS
When applied, these microscopic, carnivorous worms target the Japanese Beetle grubs (among others) and kills them before they can pupate and cause trouble.
OFT-SUGGESTED TREATMENTS WHICH ARE NOT AVAILABLE IN ONTARIO:
“Milky Spore” : Also known as Paenibacillus popilliae/Bacillus popilliae, this beneficial bacteria helps to kill beetle grubs before they become adults. As it hasn’t been approved for use in Canada, it is not available to buy or sell.
“Neem Oil“: This tree-based oil doesn’t kill adult beetles, nor does it prevent the beetles from munching on your plants. Instead, when ingested by adult beetles it affects any eggs that are laid, eventually killing the larvae before they have a chance to grow up. This is another product which hasn’t been approved for pesticidal use in Ontario, and so it cannot be bought, or sold commercially for that purpose.