Abstract
In order to know the mechanism of insect transmission of mulberry dwarf disease caused by mycoplasma-like organism in all probability, some experiments on acquisition of the causal agent by the vector of this disease, Hishimonus sellatus Uhler, were made.
When non-viruliferous H. sellatus was fed on the infected mulberry seedling, the shortest period required for acquisition of the causal agent was 3 hours. The transmission rate was increased by the extention of feeding period. If the stem was not lignified the leafhopper was able to acquire the agent from lower part of stem of the infected mulberry seedling on which the disease symptoms appeared only at the top of the stem. Though the rate was low, the causal agent was able to be acquired by the leafhopper from the infected shoots which were apparently healthy. The leafhopper could acquire the agent not only from the infected mulberry seedling planted in pot, but also from a piece of cut mulberry shoot placed in a petri dish. There was not large difference in the transmission rate between the case of seedling planted in pot and that of a piece of shoot in a petri dish. The relation between growth stage of leafhopper and acquiring rate of the causal agent was investigated. In the case of nymph, the transmission rate increased with the progress of instar, but in the case of adult, it was higher than that of 3rd instar nymph. There was no distinct relation between the acquiring rate of causal agent and the sexual difference of the leafhopper. No difference was found in the transmission rate between light and dark conditions at the time of feeding on the infected mulberry seedling.
