Epidemiology and management of kava dieback caused by cucumber mosaic cucumovirus

A dieback caused by cucumber mosaic cucumovirus (CMV) is the most important disease of kava (Piper meihysiicum) in the South Pacific. Investigations using the double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) showed that CMV is not entirely systemic within naturally infected plants in the field. In greenhouse tests, 4% of plants derived from apparently uninfected stems and 12 to 17% of plants derived from symptomatic stems tested positive for CMV after emergence and later developed symptoms and died. Analyses of the spatial distribution of naturally infected plants in the field indicated that epidemics are initiated from small clusters of diseased plants that rapidly expand and spread. A trend toward a uniform distribution of diseased plants follows. In two field plots monitored from the time of epidemic initiation, 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 indicated that a decrease in aggregation of diseased plants occurred. Disease management strategies are suggested based on the results of these Serological investigations and knowledge of the change in spatial pattern. The strategies are to combine the use of virus-free planting material, a roguing policy, and intercropping