Pilobolus crystallinus

Pilobolus crystallinus, commonly known as the dung cannon fungus, is a specialized zygomycete that plays a significant role in agricultural ecosystems. While it primarily grows on the dung of herbivores, it represents a significant challenge for farmers, as its unique spore-dispersal mechanism affects the safety and quality of forage crops grown near manured areas.

The fungus primarily impacts pasture grasses and forage legumes. It does not actively infect plant tissues in a way that causes decay, but it coats the blades of grass with sticky sporangia. This contamination makes the plants vectors for transmission of various helminth larvae (such as Dictyocaulus) to livestock that consume the contaminated vegetation during grazing.

The symptoms of infestation are highly characteristic: tiny, dark, distinct spots appear on the surface of leaves and stems. These spots are the fungal sporangia. They are densely packed with spores and firmly adhered to the plant surface, making them difficult to wash off with rain, which persists as a contamination issue throughout the growing season.

The development of this fungus is strictly dependent on specific environmental conditions: high humidity, moderate temperatures, and the availability of nutrient-rich substrate like herbivore dung. The fungus exhibits a phototropic response, directing its sporangia toward light, which triggers a high-pressure discharge mechanism that can launch spores across significant distances.

Effective management requires a combination of hygiene and grazing strategies. Key preventive measures include:

• Implementing rotational grazing to break the infection cycle.
• Proper composting of manure before application to fields to kill fungal spores.
• Maintaining optimal pasture drainage to reduce surface moisture.
• Regular mowing of pastures to remove older, contaminated growth and encourage fresh, spore-free biomass.