Bidens anthracnose

The disease is caused by the pathogenic fungus Colletotrichum bidentis, which is a member of the Ascomycota division. It is a highly specialized fungus that targets plants within the Bidens genus. This disease is typically classified as an anthracnose, resulting in tissue necrosis and potential death of the infected plant.

The primary host for this fungus is Bidens pilosa, widely known as black-jack or beggar-ticks. Due to the high specificity of Colletotrichum bidentis towards this weed, it is frequently studied as a biocontrol agent. Researchers aim to utilize this pathogen to naturally reduce weed populations in various agricultural and ecological settings.

Symptoms of the infection manifest as small, sunken spots on leaves, stems, and petioles, which eventually turn dark brown or black. As the disease progresses, the central parts of the lesions may develop small, cushion-like structures called acervuli.

• Irregular necrotic lesions on foliage
• Stem girdling causing distal wilting
• Increased susceptibility to secondary pathogens
• Overall reduction in plant biomass

The development of the fungus is strictly dependent on moisture and temperature. High relative humidity and warm temperatures facilitate the germination of conidia and the infection process. Rain splashes and wind are the primary vectors for spore dispersal, allowing the disease to spread rapidly through dense plant populations.

Regarding management, because Colletotrichum bidentis is often utilized as a natural weed suppressor, traditional farmers may view it as beneficial. However, in cases where control is necessary to prevent spread to susceptible crops, standard fungicide applications are effective. Preventive measures include field sanitation, crop rotation, and maintaining optimal plant spacing to reduce micro-humidity.