The area of Vancouver affected by Japanese beetle, City of Vancouver
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The voracious Japanese beetle will take a bite out of just about anything. With over 250 plant species on the menu for this invasive insect, the City of Vancouver and government of British Columbia is taking steps to minimize the plight of the grubs and quarantine affected soils. Learn how you can support the efforts of local authorities: How Metro Vancouver Residents Can Protect Gardens and Lawns from New Invasive Species
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Thumbnail: “Creative Commons Japanese Beetle” by Katja Schulz is licensed under CC BY-2.0 / cropped from original
Hello, thanks for your question.
In theory, nematodes would work to control grubs such as European chafer beetle larvae, Japanese beetle larvae and black vine weevil larvae.
In practice, nematodes are an unreliable control method for the following reasons:
· packaged nematodes can already be dead when purchased – shelf life and storage conditions are a factor
· in order for alive nematodes to be effective, soil temperature and moisture have to be within a specific range or the nematodes will not be successful
· these perfect soil conditions have to correspond to timing in regards to the life cycle of larvae in the soil – sometimes, nematodes are applied as the larvae are going through metamorphosis or the adults are emerging from the soil
In order for nematodes to work, there has to be a “perfect storm” of conditions and timing. This is not to say they are ineffective, I have had success with nematodes controlling weevil larvae in the past. The efficacy is variable depending on:
· storage
· handling
· application technique
· soil temperature
· soil moisture
· stage of life cycle of pest
If all of the above conditions are met at the right time, nematodes will work.
A better strategy for chafer beetle is to modify maintenance practices:
· cut longer in the summer when adults are laying eggs
· use deeper rooting turf species – e.g. tall fescue, Festuca arundinacea
· maintenance practices such as aerating, topdressing and over-seeding are good strategies
Answered by Egan Davis, Horticulture Training Program Principal Instructor
What about ‘watering’ nematodes in affected areas? Are they effective against this particular type of grub? I’ve been using them in our garden to try and control other types of grubs… I’m curious if it could help with these Japanese beetles as well.