Abstract1. The causal agent of bunchy top can be transmitted by grafting successively in series, thus proving that the etiologic agent can multiply within the host plant, and fortifying the view that the causal agent is a virus. 2. A single insect is capable of transmitting the causal agent; this also indicates that the disease is caused by a virus. 3. Movement, of the virus is rapid in an acropetal, but very slow in a basipetal direction. 4. Because of the slow rate at which the causal agent spreads downward, cutting back of trees below the affected portions has proved to be a means of restoring them to normality and productivity.
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