Defining and mitigating the impacts of Acanthococcus lagerstroemiae (Hemiptera: Eriococcidae) management on pollinators

Abstract

Crapemyrtle bark scale (CMBS) [Acanthococcus lagerstroemiae (Kuwana)] is a recently introduced pest in the United States. CMBS attacks crapemyrtle [Lagerstroemia spp. L. (Myrtales: Lythraceae)], a plant ubiquitous in southern landscapes, as the primary host. Neonicotinoid insecticides, including imidacloprid and dinotefuran, are widely used to reduce damage and spread of CMBS. Because bees and beneficial insects commonly visit crapemyrtle fIowers, this study evaluated the risk of translocation of imidacloprid and dinotefuran into pollen following a soil application. Soil applications of both insecticides were made using maximum label rate. Three timings: post-bloom/pre-dormancy (autumn), pre-bud break (winter), and post-bud break/pre-bloom (spring) were used. Pollen and leaf samples were collected from trees and analyzed using a modified QuEChERS method of LC/MS. Laboratory assays were also performed with new growth to evaluate treatment efficacy against CMBS crawlers and foliage-feeding crapemyrtle aphids [Sarucallis kahawaluokalani (Kirkaldy) (Hemiptera: Aphididae)]. Additionally, abundance and diversity of crapemyrtle’s floral visitors were analyzed in highly urban and suburban sites. Pollinators from ten families in two orders (Diptera and Hymenoptera) visited crapemyrtle over two levels of urbanization. Residues in crapemyrtle pollen exceeded the chronic oral lowest observable adverse effect concentration (LOAEC) for adult honey bees, regardless of application timing. Contact exposure to contaminated pollen poses an additional risk to bees visiting systemically-treated crapemyrtles. Application of systemically-applied neonicotinoids to control CMBS in urban landscapes increases exposure risks to pollinators. Pollinator-friendly methods of CMBS control are needed.