Southern Bean Mosaic Virus in Mexican Bean Beetle and Bean Leaf Beetle Regurgitants

Abstract

SUMMARY Induced regurgitants from Mexican bean beetles, Epilachna varivestis Mulsant, and bean leaf beetles, Cerotoma trifurcata Forster, fed on southern bean mosaic virus-infected Black Valentine bean, contained concentrations of virus comparable to those in crude sap from infected leaf tissue. The virus in regurgitant of either beetle was not inactivated by storage in vitro at room temperature for 7 days. Regurgitants inhibited infection when pooled and mixed with purified virus. When beetles were fed on Pinto bean leaves dipped in purified virus concentrations of 1 or 10 mg virus/ml buffer, the amount of virus in the regurgitants and serial transmission levels by both beetles were related to the concentration from which acquisition occurred. A reduction in transmission levels with time after acquisition feeding occurred at different rates for each species of beetle and was associated with decrease of virus in the regurgitant. Mexican bean beetles but not bean leaf beetles which had fed on bromophenol blue-impregnated leaf tissue produced blue-coloured regurgitant and deposited the dye on feeding areas.