Two factors to consider when applying fungicides for dollar spot control?

Two factors to consider when applying fungicides for dollar spot control?

• A. Wind speed and rainfall; incorporate high pH water
• B. Soil type and plant height; use only systemic fungicides
• C. Leaf wetness duration and temperature; rotate MOAs and ensure thorough coverage
• D. Time of day and humidity; don't rotate MOAs

Answer: (C)

When managing dollar spot with fungicides, two factors that directly influence both infection risk and product performance are how long leaves stay wet and the ambient temperature. Dollar spot bacteria require a moist leaf surface to germinate and infect; the longer the leaf remains wet, the greater the chance of infection and the more critical it becomes to have effective coverage and timely applications. Temperature also shapes how quickly the pathogen grows and how well a fungicide works—some products perform best within specific temperature ranges, and uptake or activity can vary with temperature. In addition, rotating modes of action and ensuring thorough coverage are essential management considerations. Rotating MOAs reduces the risk that the pathogen will develop resistance to a single mechanism of action, keeping a broader toolbox available for future seasons. Thorough coverage ensures that the fungicide is present on the leaf surfaces where dollar spot occurs, maximizing protective barriers and the potential for systemic products to move to the target sites. The other options don’t align as closely with the disease biology and resistance management. Wind speed and rainfall affect spray deposition and wash-off but don’t address the infection conditions on the leaf surface as directly as leaf wetness duration. Soil type and plant height are not primary factors for a foliar turf disease, and relying on only systemic products ignores the value of protective coverage. Time of day is less critical than the actual leaf wetness period, and not rotating MOAs increases resistance risk.

When managing dollar spot with fungicides, two factors that directly influence both infection risk and product performance are how long leaves stay wet and the ambient temperature. Dollar spot bacteria require a moist leaf surface to germinate and infect; the longer the leaf remains wet, the greater the chance of infection and the more critical it becomes to have effective coverage and timely applications. Temperature also shapes how quickly the pathogen grows and how well a fungicide works—some products perform best within specific temperature ranges, and uptake or activity can vary with temperature.

In addition, rotating modes of action and ensuring thorough coverage are essential management considerations. Rotating MOAs reduces the risk that the pathogen will develop resistance to a single mechanism of action, keeping a broader toolbox available for future seasons. Thorough coverage ensures that the fungicide is present on the leaf surfaces where dollar spot occurs, maximizing protective barriers and the potential for systemic products to move to the target sites.

The other options don’t align as closely with the disease biology and resistance management. Wind speed and rainfall affect spray deposition and wash-off but don’t address the infection conditions on the leaf surface as directly as leaf wetness duration. Soil type and plant height are not primary factors for a foliar turf disease, and relying on only systemic products ignores the value of protective coverage. Time of day is less critical than the actual leaf wetness period, and not rotating MOAs increases resistance risk.