The use of abrasives in the transmission of plant viruses

The effect of different abrasives on the transmissibility of several plant viruses was tested. Celite and animal charcoal were as effective as carborundum in increasing the number of lesions produced by a given inoculum: 400-mesh carborundum was the most effective among the different sizes which were tested; this gave a result equivalent to increasing the virus content a hundred times. Some preparations of carborundum and charcoal reduced infectivity.
Uninjured plants resisted infectivity when virus solutions were sprayed over them. Leaves previously nibbed without abrasives developed only few lesions whereas leaves rubbed with abrasives developed large numbers. Three hours after rubbing with abrasives leaves had regained their resistance to sprayed virus solutions.
The effects of rubbing leaves with abrasives are described and their significance discussed.