Tip for Controlling Root Weevils

Photo courtesy of
Portland Nursery

 I had time to work in the garden last week and noticed that I have several species of plants—rhododendron, salal, and bergenia—with notched leaves, a sure sign of a root weevil infestation. I don’t use chemicals in my garden so I was perplexed as to how to address the issue. I’ve tried beneficial nematodes in the past, but I don’t have confidence that I’m applying them correctly. However, they are touted to be effective against a number of pests that live in the soil, including weevil larvae.

Sticky barriers such as Tanglefoot is also a non-chemical option but this method of control will not work if there are access routes other than the stem to the plant such as other plants, fences, etc., which is the case in my garden because I have a tendency to pack plants into my garden spaces.

As it happens, I was flipping through the summer issue of the American Rhododendron Society Journal and saw this root weevil tip (reprinted from the Vancouver Chapter March 2010 newsletter): “Chuck Floyd, of the Peace Arch Chapter, stated that he controls weevils by spreading birdseed under his rhodos [sic]. The birds are attracted to the seed, and presumably eat the weevils and other pests at the same time.” I like that idea! He also suggests using non-sprouting seeds, which means you’ll probably need to microwave or heat the seed to prevent germination. It certainly would be easier than spending the night in the garden with a flashlight looking for various forms of weevils on your plants.

For more information on the life cycle and control of weevils, check out this excellent article: www.rhododendron.org/v54n4p195.htm. I learned that while the leaf damage adult weevils make isn’t detrimental to the health of the plant, just its aesthetics, that’s not the case with the larvae, which can damage the root systems.

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