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Quick Drying Versus Washing in Virus Inoculations. C. E. Yarwood, Professor, Department of Plant Pathology, University of California, Berkeley 94720; Phytopathology 63:72-76. Accepted for publication 26 July 1972. DOI: 10.1094/Phyto-63-72.

Washing and quick drying of inoculated leaves have separately and in combination increased virus infection under certain conditions, and decreased infection under other conditions, with 15 virus:donor host:indicator host combinations. Increases in infection due to quick drying were up to 3,060-fold in a single test, were greater with cowpea than with any other indicator host, with cucumber mosaic than with any other virus, greater with young than with old cowpeas, greater with concentrated than with dilute inoculum, greater with inoculum from apical than from basal donor cucumber leaves, greater with concentrated, than with dilute Celite, greater if plants were placed in dark rather than in light after inoculation, greater for inoculations made about midday than at other times, greater with inhibitors such as buckeye juice in the inoculum, and greater with inoculum containing caffeine, K2SO3, or Mg2Si3O8 than with inoculum containing K2HPO4 or sucrose. The washing of leaves after inoculation caused up to 600-fold increase in infection, and the conditions favoring high increases in infection due to washing were usually similar to those causing high infection due to quick drying. Washing for more than 10 sec decreased infection. Washing or quick drying reduced plant injury caused by chemicals in the inoculum, and contributed to the ease of counting lesions.