Ilarviruses: Evidence for Rapid Spread and Effects on Vegetative Growth and Fruit Yields of Peach Trees. J. K. Uyemoto, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, University of California, Davis 95616. W. K. Asai, and C. F. Luhn. Farm Advisor, Cooperative Extension, University of California, Modesto 95355; and USDA-ARS, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 76:71-74. Accepted for publication 24 July 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992. DOI: 10.1094/PD-76-0071.

Over a 4-yr period, the incidence of trees infected by prune dwarf virus (PDV) and Prunus necrotic ringspot virus (NRSV) in two young peach (Prunus persica) orchards progressed from 27 to 94% in one subplot and from zero to 72% in the other. For trees infected with peach stunt disease (PSD = infections by PDV and NRSV), fruit production, trunk diameter, and tree height were reduced by an average of 30, 23, and 12%, respectively, over 3 yr. Single virus infections by NRSV, but not PDV, also significantly affected tree growth and fruit yield. Honeybees tested positive for both viruses and are likely involved in transporting virus-contaminated pollen to healthy trees.