NONCIRCULATIVE TRANSMISSION OF PLANT-VIRUSES BY LEAF-FEEDING BEETLES

The movement of four plant viruses into the hemocoel of chrysomelid and coccinellid beetle vectors after ingestion was studied. None of the four plant viruses (two beetle-transmissible and two non-beetle-transmissible) were detected in the hemolymph of the Mexican bean beetle (Epilachna varivestis), an efficient plant virus vector in the family Coccinellidae, regardless of the acquisition source, type of virus, or method of virus detection. The infectivity of viruses was not destroyed by the hemolymph of the Mexican bean beetle, as demonstrated by virus survival in hemolymph for up to 3 days after virus injection into the hemocoel. Only one beetle-transmissible and one non-beetle-transmissible virus tested were found in the hemocoel of the bean leaf beetle (Cerotoma trifurcata) and the spotted cucumber beetle (Diabrotica undecimpunctata howardi), both members of the family Chrysomelidae. These results indicate that virus movement into the beetle hemocoel is determined by the nature of the interaction between the individual virus and beetle, and that some plant viruses that are noncirculative, such as bean pod mottle comovirus, can be efficiently transmitted by beetle vectors.