The potential role of native weed species and bumble bees (Bombus impatiens) on the epidemiology of Pepino mosaic virus.
Surveys of native weed species growing in and within 30 m of tomato greenhouses infected with Pepino mosaic virus (PepMV) identified Solanum dulcamara (climbing nightshade), Solanum nigrum (black nightshade), and Solanum ptycanthum (eastern black nightshade) as susceptible host plants. All plants exhibited mild mosaic symptoms and virus was back-inoculated and confirmed in tomato (Lycopersicon esculentum). In transmission tests using both mechanical methods and bumblebees (Bombus impatiens), S. ptycanthum, Solanum sarrachoides (hairy nightshade), and Datura stramonium (jimsonweed) were infected. Weak positive assays by ELISA or DRT-PCR for Amaranthus blitoides (prostrate pigweed), Chenopodium album (lamb's-quarters), and Plantago lanceolata (narrow-leaved plaintain) were possibly a result of either a hypersensitive localized response to infection or low level virus contamination by bees since the virus could not be recovered by back-inoculation into tomato. Bumblebees exposed to PepMV infected D. stramonium, S. ptycanthum, and S. sarrachoides successfully transmitted the virus back into the tomato. No over wintering perennial weed species were found to be natural hosts of PepMV, and build up of inoculum in the field is unlikely. Weeds do not appear to represent a significant role in the epidemiology of this disease in Ontario.