Pathogen identification of anthracnose disease on Millettia speciosa and indoor determination of fungicide toxicity

Objective  To determine the pathogen causing anthracnose disease on Millettia speciosa and screen effective fungicides.

Method  Tissue isolation method was used to isolate the pathogen. The pathogenicity was tested according to Koch’s rule after purification. The pathogen was identified based on morphological characteristics and multi-locus sequence analysis. Furthermore, the sensitivity of this pathogen against four common fungicides was measured according to the mycelial growth rate.

Result  Two out of six obtained isolates could infect M. speciosa leaf and caused brown spot. Combining morphological characteristics and multi-locus sequences analysis, the pathogen caused anthracnose disease on M. speciosa was identified as Colletotrichum siamense. This pathogen was highly sensitive to difenoconazole, prochloraz, pyraclostrobin and thiophanate-methyl with EC₅₀ values below 0.1 mg/L, and prochloraz showed the highest efficacy with EC₅₀ of 0.015 mg/L.

Conclusion  The pathogen causing anthracnose disease on M. speciosa is C. siamense, and difenoconazole, prochloraz, pyraclostrobin and thiophanate-methyl can be applied to control anthracnose disease in the field.