Sweet Potato Witches’ Broom and Legume Little-Leaf Diseases in the Solomon Islands. G. V. H. Jackson, Plant Pathologist, Dodo Creek Research Station, Ministry of Home Affairs and National Development, Honiara, Solomon Islands. F. W. Zettler, Professor, Plant Pathology Department, University of Florida, Gainesville 32611. Plant Dis. 67:1141-1144. Accepted for publication 20 April 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1141.

Sweet potato witches’ broom disease occurred in Ipomoea batatas, I. indica, I. triloba, and Merremia pacifica in the Solomon Islands. The disease agent, a mycoplasmalike organism (MLO) found in phloem cells of infected I. batatas plants, was transmitted by the sweet potato black-spotted leafhopper. Orosius lotophagorum ryukyuensis. Disease incidence was much higher on the Guadalcanal Plains than elsewhere in the Solomon Islands. The high incidence there was correlated with high populations of O. lotophagorum ryukyuensis. All 192 accessions of I. batatas from the Solomon Islands were susceptible to this MLO when graft-inoculated with infected scions or when infected naturally. Legume little-leaf, another MLO, was manifested as a witches’ broom symptom in Emilia sonchifolia and Vernonia cineria. On Guadalcanal, the legume little-leaf disease was also found in plants of Crotalaria sp., Desmodium heterophyllum, D. triflorum, Polygala paniculata, and Vigna sesquipedalis. This is the first report of the legume little-leaf disease in the Solomon Islands, and Orosius argentatus was shown to be a vector. The legume little-leaf agent was not shown to infect Ipomoea spp., and the sweet potato witches’ broom agent was not shown to infect any of the hosts of the legume little-leaf MLO.