Bee-Mediated Transmission of Blueberry Leaf Mottle Virus Via Infected Pollen in Highbush Blueberry

Abstract

Individual highbush blueberry bushes [Vaccinium corymbosum L. ''Jersey''] were tested by enzyme-linked immunosorbent assay (ELISA) for blueberry leaf mottle virus (BBLMV) infection in a commercial planting. The pattern of infected bushes was random, suggestive of a mode of spread different than by nematodes. Blueberry aphids allowed either a 72-hr or a 120-hr acquisition access period on BBLMV-infected blueberry failed to acquire detectable amounts of BBLMV when individuals were tested by radioimmunosorbent assay (RISA). Hand pollination of 15 2-yr-old blueberry plants resulted in infection of shoots of one of the plants. Trapping foraging honeybees from bushes in a commercial field containing BBLMV-infected bushes resulted in BBLMV being detected in the pollen from up to 51.4% of the pollen baskets from the bees legs when tested by ELISA. In field experiments, transmission occurred during bloom during a 2- to 3-wk period from BBLMV-diseased source bushes to young, virus-free potted bushes placed around a source bush. A hive of bees was placed within a cage around the bushes. Lower levels of transmission occurred if the hive and bushes were not caged, or if the bushes were caged, but without a hive. Virus-free potted bushes placed around a healthy source bush (in a field known to be free of BBLMV) and caged with a hive of bees inside remained virus-free. Blueberry leaf motile virus appears to be spread mainly by foraging honeybees, which carry BBLMV-contaminated pollen.