First report of bacterial wilt caused by Ralstonia solanacearum on Eucalyptus sp. in Paraguay.
Bacterial wilt, caused by Ralstonia solanacearum, is a major disease of eucalyptus and was first reported on this host in Brazil in 1983. Crop losses that average 30 to 40% are frequently reported after initial outbreak reports. In March 2011, eucalyptus trees with typical symptoms of bacterial wilt were observed in Caaguazú and San Pedro states, located in the Central and Northern regions of Paraguay, respectively. Plants were wilted and foliar necrosis or defoliation of the lower portion of the canopy was common. Transverse sections of the trunk revealed browning of the xylem vessels forming dark rings. Based on morphological and biochemical characteristics, molecular investigations (PCR assay and sequence analysis) and pathogenicity tests, the causal agent was identified as R. solanacearum. This is thought to be the first report of eucalyptus bacterial wilt in Paraguay and serves as a warning to other properties in the country and in South America.