Symptomless Infection and Incidence of Maize White Line Mosaic. Raymond Louie, Research Plant Pathologist, ARS, USDA, Department of Entomology, Ohio Agricultural Research and Development Center and The Ohio State University, Wooster 44691. D. T. Gordon, Professor, and L. V. Madden, Systems Specialist, Department of Plant Pathology, and J. K. Knoke, Research Entomologist, ARS, USDA, Department of Entomology, Ohio Agricultural Research and Development Center and The Ohio State University, Wooster 44691. Plant Dis. 67:371-373. Accepted for publication 26 August 1982. 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, 1983. DOI: 10.1094/PD-67-371.

Symptomless infections in sweet corn (Zea mays) from three field plantings with a history of maize white line mosaic (MWLM) were detected by enzyme-linked immunosorbent assays (ELISA) for the virus. Symptomless infections were detected similarly in two of three fields where MWLM was not previously found. The numbers of plants with symptomless infections in a sample of 15 consecutive plants within a row were 13/15, 11/15, and 7/15, and 4/15, 1/15, and 0/15 for three fields with and without a history of MWLM, respectively. Two plants with characteristic symptoms of MWLM were included in samples from each field with a known history of MWLM and were positive for maize white line mosaic virus (MWLMV) infection in ELISA. In experimental plantings, symptomless infections were detected by ELISA in root samples as early as 10 days after planting (DAP) and 100% were assayed positive by 55 DAP in two of four plantings. Symptomless shoot infections (~13%), based on ELISA of leaf samples, were detected by 40 DAP in the same two plantings. Disease incidences based on symptoms were low (<10%) for all planting dates except the third planting, where it reached ~20% level. Infections appeared to be more dependent on the time of season at which the plants were growing than on plant age. Detection of symptomless infection in plants and observations of plants with characteristic symptoms indicate that symptom development depends on some factor in addition to MWLMV infection.