Sugarcane Mosaic Virus in Kenya

Abstract

LOUIE, R. 1980. Sugarcane mosaic virus in Kenya. Plant Disease 64:944-947. Surveys for sugarcane mosaic virus (SCMV) in maize (Zea mays L. subsp. mays) were made in 34 of 41 districts in Kenya. SCMV was found in 20 districts and only in the western plateaus, Central Highlands, and Rift Valley. Provinces with high incidence of SCMV included Nyanza (15.2%), Rift Valley (15.8%), and Western (19.6%). SCMV was not found in Coast or Nairobi provinces. The incidence of SCMV was higher in late-planted maize planted for the April-May rains or the October-November rains than in early plantings. This is the first report of natural infection with SCMV in Cynodon dactylon, C. nlemfunsis, Digitaria nuda, D. abyssinica, Eragrostisexasperata, Paspalum notatum, P. scrobiculatum, Rhynchelytrym repens, and an unknown Tripsacum fasciculatum cross. The distribution of SCMV in maize appeared to be related to the distribution of sources of inoculum, but the periodicity of disease development appeared to be related to vector populations. Maize streak and maize mosaic viruses were most often found in Central (4.5%) and Coast (13.8%) provinces. Additional key words: corn, maize dwarf mosaic virus, weed hosts In 1973, Kulkarni (14) reported sugarcane mosaic virus (SCMV) in sugarcane (interspecific hybrids of Saccharum) and maize (Zea mays L. subsp. mays) in six of 41 districts of Kenya and in Tanzania and Uganda. Because SCMV causes serious losses in maize (14, 16), which is grown in most parts of Kenya (1), more information was needed to delineate the distribution of SCMV and determine its possible overseasoning hosts. We report on the distribution of SCMV in maize in Kenya, the seasonal development of the disease at Muguga and Kitale, and the possible sources of inocula. SCMV includes strains specially adapted to sugarcane, maize, or sorghum (Sorghum spp.) that are difficult to transmit from one grass host to another; for example, maize dwarf mosaic virus strain A is easily transmitted to johnsongrass (S. halepense (L.) Pers.) but not to sugarcane (23). No attempt was made in this paper to identify strains. A preliminary report on weed hosts has been published (18). MATERIALS AND METHODS One-hundred maize plants along an edge row of each field and 100 plants Present address of the author: AR, SEA, USDA, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster, OH