Alternative means of controlling chafer beetles
European chafer beetle larvae has been ruining lawns in Vancouver, and people are understandably desperate to prevent the damage that chafers and their predators can cause. In some cases, commercial lawn maintenance companies are brought in to rid lawns of these destructive grubs. Unfortunately, homeowners may not know what these commercial firms are actually doing in their backyards.
Most people know that Vancouver has bylaws prohibiting the use of cosmetic pesticides. What they may not know is that the potential damage caused by chafer can be seen as reducing property values, and because of this there is an exemption for the use of certain pesticides on lawns. In most cases, the pesticide (Merit—chemical name Imidacloprid) that is used by lawn maintenance companies is in a class of compounds known as neonicotinioids, or commonly, “neonics.”
Although neonicotinioids were originally touted as relatively safe pesticides (they are celebrated for their low mammalian toxicity—indeed, neonics remain the treatment of choice for flea control on dogs and cats), their use has been implicated in the decline of honey bees. While this is a much contested subject, an increasing number of jurisdictions have either banned neonics outright, or severely curtailed their availability or use.
There are alternatives to managing European chafer beetle larvae. Simple activities such as allowing the grass to grow longer in the summer, and over-seeding with appropriate grass species and grass substitutes can be very effective management strategies. Applying pesticides may kill chafer grubs, but spraying ignores a set of larger issues. For example, the magnitude of collateral damage to non-target organisms is not well understood. However, it is suspected that other soil-dwelling insects and the birds that eat them are adversely affected.
Kerrie van Gaalen, UBC Botanical Garden staff member, has recently published an article that details appropriate chafer beetle management strategies.
Submitted by Douglas Justice, Associate Director, Horiculture and Collections, April 28, 2016