Secondary dissemination of konnyaku [Amorphophallus rivieri] bacterial leaf blight caused by Pseudomonas pseudoalcaligenes subsp. konjaci

Secondary dissemination of konnyaku bacterial leaf blight was studied. In inoculation tests, symptoms appeared only on the leaflet of konnyaku without regard to the spray or wound inoculation method used. From these results, it seemed that this disease occurred with stomatal and wound infections. The rain drops dripping from diseased leaflets contained the bacteria at so high concentration (105-106cfu/ml). In dissemination tests under the rainfall condition, it was confirmed that the causal bacteria were spread and attacked the konnyaku leaflets at 2.5m from the inoculum source in the maximum velocity of 7.2m/sec and the precipitation of 88.7mm/day. The dissemination of the disease was also certified by the contact with the diseased leaflet. From the results obtained, it was concluded that both the splash dispersal of causal bacteria by the wind and rain and the contact dissemination with the diseased leaflets would be possible ways of secondary dissemination of konnyaku bacterial leaf blight.