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Tobacco and Tomato Ringspot Viruses and Their Relationships with Tetranychus urticae. Carlos R. Granillo, Graduate Student, Department of Plant Pathology, The Pennsylvania State University, University Park 16802, Present address of senior author: Departamento de Parasitologia Vegetal, Facultad de Ciencias Agronomicas, Universidad de El Salvador, San Salvador, El Salvador, C. A; Samuel H. Smith, Associate Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 64:494-499. Accepted for publication 25 October 1973. DOI: 10.1094/Phyto-64-494.

The two-spotted spider mite Tetranychus urticae failed to act as a vector of tobacco ringspot virus (TRSV) and tomato ringspot virus (TomRSV). A total of 4,210 mites did not transmit TRSV and 1,800 mites failed to transmit TomRSV. Tobacco ringspot virus, but not TomRSV was detected in mites, when homogenates of acquisition-fed mites were used for mechanical inoculations. In 10 trials, an average of 4.9 local lesions per cotyledon was obtained when 1.0 ml of each homogenate was rubbed on 10 cotyledons. Exposing mites for 10 min, 15 min, or 1 h to 2% formaldehyde; and to a 1:16 dilution of antiserum for 30 min, 1 h, or 24 h prior to homogenizing did not reduce the number of local lesions. The virus remained infective in the mites for at least 24 h. No virus could be recovered from mite feces. Tobacco ringspot virus was not acquired by mites from purified preparations, nor was it released by mites carrying TRSV.