EFFECT OF IONIC CONCENTRATION ON INFECTIVITY OF A VIRUS OF CITRUS RED MITE PANONYCHUS CITRI

A virus disease of the citrus red mite, Panonychus citri, is most infective in an aqueous suspension when the pH is between 5.0 and 7.0. Within the apparently optimum range of 5.6-6.6, viral stability was not immediately affected by salt at the concentrations tested, but in slightly alkaline solutions, viral inactivation was proportional to the concentration of salt in the suspending solution. In 0.017 m phosphate buffer, infectivity occurred at pH 8.0; in 0.033 m buffer, the upper limit was 7.6. After storage for 2 days at 10°C, the upper limit was reduced to 7.0. The effect of time on virus subjected to varied pH and concentrations of salt was dependent on storage temperature. When storage was at 10°C, activity occurred at pH 7.0 after 14 days in the most concentrated buffer. Material stored 2 days at 28°C was infective at pH 7.0 in only the most dilute buffer; after 5 days all suspensions were adversely affected. © 1968.