Trichiales slime molds

Trichiales are an order of myxomycetes, commonly known as slime molds, which occasionally impact agricultural production. While they are essentially decomposers that live on organic matter, their ability to colonize the surface of living plants makes them a subject of concern for agronomists aiming to maintain optimal plant vitality.

The causal agents are specialized organisms that transition through a plasmodial phase before producing sporocarps. The damage is primarily mechanical; by forming dense crusts on stems and leaves, they suppress the biological functions of the plant, including photosynthesis and respiration, which leads to reduced yields.

A wide variety of crops can be affected, ranging from greenhouse vegetables to ornamental plants and lawn grasses. These organisms thrive in high-humidity environments, especially where decaying mulch or dense canopy layers provide sufficient moisture and protection for the organisms to complete their life cycle.

Symptoms are easily identifiable as powdery or crusty deposits in shades of yellow, orange, or brown appearing on the lower foliage. These deposits are, in fact, the reproductive structures (sporocarps) of the slime mold, which release millions of microscopic spores into the air when disturbed.

Management and prevention focus on eliminating the conditions that favor their growth. This includes improving air circulation around plants, reducing surface irrigation moisture, and removing rotting vegetation from the soil surface. Applying appropriate systemic fungicides can also help manage heavy outbreaks in commercial greenhouses.