1989 Volume 55 Issue 5 Pages 609-614
The investigation was conducted to make clear the infection sources of the bacterial leaf blight of konnyaku (Amorphophallus konjac) caused by Pseudonomas pseudoalcaligenes subsp. konjaci. Survival of the pathogenic bacterium in the diseased leaflets, on corms and in soil was determined by using a selective medium. The bacterium could be isolated from the diseased leaflets kept for 422 days on the soil surface of natural field, but not be isolated 106 days after the leaflets were buried at a depth of 5cm in field soil. As the result of application of debris of the diseased leaflets onto soil surface of field immediately after planting corms, the disease occurred obviously on new leaflets grown from corms planted. When artificially infested corms were preserved at 10C of room temperature or in natural field soil, the bacterium could be recovered until 150 days after, namely until Apr. 14 in next spring. Survival of the bacterium in soil was longer at 5C than at 25C, but the bacterium could not be detected after 60 days at 5C in natural field. These results indicate that the residues of diseased leaflets and corms infested with this bacterium may be served as main infection sources of the next konnyaku cultivation.