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Aphid Nymphs Transmit an Isolate of Barley Yellow Dwarf Virus More Efficiently than do Adults. C. C. Gill, Research Scientist, Canada Department of Agriculture, Research Station, 25 Dafoe Road, Winnipeg 19, Manitoba. Phytopathology 60:1747-1752. Accepted for publication 3 July 1970. DOI: 10.1094/Phyto-60-1747.

The proportion of 12-hour-old nymphs of the corn leaf aphid, Rhopalosiphum maidis, that transmitted an isolate of barley yellow dwarf virus specific for this aphid was consistently larger than the proportion of adults that transmitted. This ratio was higher for acquisition feeding periods of 1 and 2 days than for longer feeding periods. Apterous adults of Rhopalosiphum maidis transmitted the virus to more test seedlings than did alate adults. When aphids were allowed access to the virus source plants as 12-hour-old nymphs, the percentage of plants infected by both alate and apterous adults was considerably higher than when the aphids acquired virus as adults. Young nymphs of the greenbug, Schizaphis graminum, were also more efficient vectors for this isolate than adults, but there was no significant difference between the efficiency of nymphs and adults of Macrosiphum avenae or Rhopalosiphum padi. Nymphs of Rhopalosiphum maidis were also more efficient vectors than adults for three other R. maidis-specific virus isolates, but not for a fourth.