Dr. Maria Tomaso-Peterson’s presentation on diseases of Southern residential and commercial turfgrasses covered several key points:
- Introduction to Plant Pathology: She emphasized the importance of understanding the complex system of plant pathology, including the susceptible host (turfgrass), the pathogen, and the conducive environment. The environment, including temperature, moisture, and physical aspects, significantly influences disease occurrence.
- Large Patch Disease: Introduced by the soil-borne fungus Rhizoctonia solani, large patch affects warm-season turfgrasses, causing radial growth and bright orange coloration. It’s most prevalent in September to November and April to May, depending on the environment. High nitrogen levels and poorly drained soil are conducive to its spread.
- Brown Patch Disease: Similar to large patch but affects cool-season grasses. It’s caused by the same fungus but is less prevalent in the Deep South.
- Fungicide Management: She discussed the use of various fungicides for managing large patch, including quinolone sulfonamides (QSIs) and demethylation inhibitors (DMIs). The timing and application volume are crucial for effective control.
- Foliar Diseases: Mentioned dollar spot and leaf spot, which are prevalent in Bermuda and zoysia grasses. These diseases are influenced by temperature, humidity, and nitrogen levels.
- Take-All Root Rot: A root-borne disease caused by Gyromitra grisea, affecting St. Augustine and centipede grasses. It’s more challenging to manage due to its root-based nature. Cultural and chemical management practices are recommended.
- Gray Leaf Spot: A disease affecting St. Augustine grass, caused by Curvularia malinah. It thrives in high temperatures and humidity. Cultural and chemical management, including proper irrigation timing and nitrogen application, are key to controlling it.
- Nitrogen Management: For Bermuda and zoysia grasses, she advised on the appropriate amount of nitrogen application throughout the growing season, emphasizing the importance of timing and slow-release formulations.
- Preventive Fungicide Application for Spring Dead Spot: Discussed the possibility and timing of applying fungicides to prevent spring dead spot, especially in areas with mild winters.
Dr. Tomaso-Peterson’s presentation highlighted the importance of understanding the specific diseases affecting turfgrasses in the Southern United States, the environmental factors that influence their occurrence, and the management strategies, including fungicide application and cultural practices, to control these diseases effectively.