CAUSED BY CUCUMBER MOSAIC CUCUMOVIRUS

A dieback caused by cucumber mosaic cucumovirus (CMV) is the most impo rtant disease of kava (Piper methysticum) in the South Pacific. Invest igations using the double antibody sandwich enzyme-linked immunosorben t assay (DAS-ELISA) showed that CMV is not entirely systemic within na turally infected plants in the field. In greenhouse tests, 4% of plant s derived from apparently uninfected stems and 12 to 17% of plants der ived from symptomatic stems tested positive for CMV after emergence an d later developed symptoms and died. Analyses of the spatial distribut ion of naturally infected plants in the field indicated that epidemics are initiated from small clusters of diseased plants that rapidly exp and and spread. A trend toward a uniform distribution of diseased plan ts follows. In two field plots monitored from the time of epidemic ini tiation, Lloyd's patchiness index fell from 14 to 2 after 25 weeks in the first plot and from 42 to 6 after 24 weeks in the second. This ind icated that a decrease in aggregation of diseased plants occurred. Dis ease management strategies are suggested based on the results of these serological investigations and knowledge of the change in spatial pat tern. The strategies are to combine the use of virus-free planting mat erial, a roguing policy, and intercropping.