Ecological characteristics and biological control of mulberry anthracnose

To develop effective control techniques against mulberry anthracnose caused by Colletotrichum dematium, ecological and biocontrol studies on the disease were carried out. It was confirmed that the causal fungus overwinters mainly in infected mulberry leaves on the ground, then first infects the leaves adjacent to the ground in the rainy season. The fungal infection secondarily reaches the middle and upper foliage of mulberry trees with the passage of time, being less associated with the leaf age. The diseased leaves subsequently fall in autumn, and the fungus overwinters in these leaves again. It was suggested that the removal of fallen leaves from the mulberry field in autumn may contribute to cutting off the above disease cycle efficiently. A potential antagonist, Bacillus amyloliquefaciens strain RC-2, was isolated from healthy mulberry leaves. The antagonism was due to the production of antifungal compounds by the strain. Seven kinds of antifungal compounds were purified, and one of these was identified as iturin A2. Based on antagonistic mechanisms of the strain, the inhibition ability of RC-2 could be efficiently used by the application of the strain onto the leaves adjacent to the ground when primary fungal transmission from soil occurs. Furthermore, the antibiotics inhibited several other phytopathogenic fungi and bacteria, besides C. dematium, in vitro, suggesting that the antibiotics produced by RC-2 might be useful as multiple control materials against various plant diseases.