Gymnoascus reessii

Gymnoascus reessii is an ascomycete fungus commonly recognized in agricultural science as a mold pathogen. Primarily known as a saprotrophic organism that degrades organic material, it can become a detrimental agent for crops, especially when agricultural commodities are stored under suboptimal conditions.

The fungus affects a variety of field crops, including wheat, barley, corn, and oilseeds. It is particularly notorious for colonizing seed lots that have not been adequately dried, leading to rapid deterioration of seed quality, viability, and potential germination rates if these seeds are used for planting in the following season.

Symptoms of an infection include the development of a surface fungal bloom on the seed coat or plant debris. Initially, the growth may look like fine, fuzzy white threads, which eventually transition into a brownish or yellowish powdery layer consisting of fungal spores. Contaminated batches typically exhibit a noticeable musty or earthy odor, indicating significant degradation.

The development of Gymnoascus reessii is highly dependent on environmental factors, specifically moisture and temperature. High relative humidity (often exceeding 75%) and warm temperatures are key catalysts for rapid growth. The fungus is highly resilient, and its spores can survive in soil or on warehouse surfaces for extended periods, making sanitation a critical issue in modern agricultural practice.

Prevention and management require a focus on moisture control and hygiene. Essential protective measures include:

• Drying all harvested grain and seeds to a safe moisture content below 14% prior to storage.
• Maintaining proper airflow and monitoring temperature levels in grain storage facilities to prevent hotspots.
• Applying systemic fungicides during seed treatment to protect seedlings from soil-borne pathogens.
• Practicing strict crop residue management to minimize the overall inoculum load in the field.