Myxomycetes

Myxomycetes (Mycetozoa), commonly known as slime molds, are unique organisms that behave like amoebae in their active phase and like fungi in their reproductive phase. While not traditional pathogens that feed on living plant tissues, they can act as problematic surface contaminants that disrupt plant physiology.

The primary concern regarding these organisms is the formation of plasmodia on the lower leaves and stems of crops. This mass physically coats the plant surfaces, effectively blocking stomata and obstructing photosynthesis, which stunts the plant's growth and makes it more vulnerable to secondary bacterial infections.

Commonly affected crops include strawberries, bedding plants, and various vegetable seedlings in humid greenhouse conditions. The initial symptoms appear as white, yellow, or translucent slimy patches on stems or soil surfaces, which eventually harden into dry, crusty spore-bearing structures.

Development is highly dependent on environmental factors, specifically high moisture levels, poor soil drainage, and stagnant airflow. Slime molds thrive in shaded, damp areas where organic matter is abundant, making them a common sight in poorly ventilated greenhouses or during prolonged wet spells.

Effective control measures focus on cultural practices rather than chemical treatments. Key strategies include improving drainage, increasing plant spacing to enhance airflow, and removing mulch or debris that allows the plasmodia to climb onto the crop. In severe cases, physical removal of the visible plasmodium can help limit further spore distribution.