Black Vine Weevil Threat to Sarracenia in Oregon: Monitoring and Biological Control

An Oregon (southern Willamette Valley) grower asks about black vine weevil damage to Sarracenia rhizomes, noting weevils on rhododendrons. Jeff Dallas hasn't seen them as a problem in northern Willamette Valley—weevils may dislike wet peat media. If treatment needed, acephate (systemic) is first choice since damage isn't immediately visible.

Follow-up: Grower keeps bees, prefers non-chemical. Asks if 24–48 hour submersion (above rhizome, shaded, cool fall day) drowns larvae without causing rot. Dallas: Submersion likely works—weevils attack non-aquatic plants. References PNW Insect Management Handbook (link) recommending predatory nematodes for container stock. Asks if grower actually finds grubs or rhizome damage.

Biological control (nematodes) is bee-safe and effective for soil-dwelling larvae. Submersion exploits Sarracenia's semi-aquatic tolerance.