A common pest we’ve been encountering for the past several years has been the Japanese beetle (Popillia japonica). It feeds on a wide variety of plants including beans, eggplant, roses, grapes, and more. Here’s what you need to know about these insects and how you can prevent them from decimating your garden this year.

Japanese beetles are usually about 1.5cm long and 1cm wide. These winged insects have an iridescent copper coloured back with green thorax and head. Their irridescent-coloured back is one of the main distinguishing features of these beetles. Plant damage by these beetles are typified by skeletonized foliage, whereby the leaf material is eaten, leaving just the veins of the leaf intact. Individual beetles do not usually pose a threat to the plant, but due to the gatherings in large numbers, significant damage can be done by a sizable population

The main reason these beetles are a pest is that they are not native to North America. In Japan where they originate, they are much less of a pest due to the adaptation of local predators.

If you’ve encountered Japanese beeltes in your garden, chances are good you will see them again the following year. Their larvae live in the ground and feed off roots of grasses and emerge in late June to mid July to feed on your plants.

To control Japanese beetles, you can hand pick the adults and drown them in a bucket of soapy water if the population is manageable or controlled to a few plants. For larger infestations, a spray can also be made using insecticidal soap and/or neem oil. Ensure the spray comes in direct contact with the beetles. Pheremone traps are often ineffective and can even increase the pest outbreak due to many beetles not landing in the trap as they are clumsy fliers.

For more information on Japanese Beetles, OMAFRA has some additional information: http://www.omafra.gov.on.ca/english/crops/facts/92-105.htm

Cover Image by Michael Gil, used under its Creative Commons license.

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