Protecting Container-Grown Crops from Black Vine Weevil Larvae with Bifenthrin

Abstract

Preplant incorporation of Talstar 0.2G (bifenthrin) can prevent root weevil and white grub infestations in container-grown nursery crops. Under some conditions, control failed in greenhouse experiments with black vine weevils. A low-density potting medium with 10 ppm of bifenthrin allowed 14–66% as many black vine weevil larvae to develop on Astilbe, Heuchera, Sedum, Taxus, and Thuja root systems as in an untreated medium. The greatest larval survival was in Sedum, which supported rapid development of larvae as internal feeders. A preplanting dip of roots into an 800 ppm bifenthrin suspension was itself very effective (91–99% control of larvae), and provided additive benefit with preplant potting mix incorporation of Talstar 0.2G. In a comparison of bulk-density based dosing and volume-based dosing of potting media, the best regression model used solely the volume-based dosage for estimating the resulting average larval population, while the weight-based dosage gave a simple relationship for estimating the maximum larval survival. Preventing black vine weevil development requires incorporation of 32 ppm of the granular bifenthrin product into potting media.