Summer is in full-swing, and the growing season is well underway for turf managers. While conditions this time of year are often ideal for growing turf, it also means ideal conditions for fungal diseases to grow and infect healthy turf are approaching.
Every disease problem requires three factors for infection to occur:
Turf managers do their best to keep the host (i.e., the turf) as healthy as possible. They also manage environmental conditions through a variety of cultural practices – mowing, dew removal, efficient irrigation, air circulating fans – to maximize the health of the turf and minimize the potential for diseases to infect the stand. Despite those efforts, there will be periods where infection will occur. Fungicides are a very valuable tool to control pathogens in the quest to maintain healthy, uniform, green turfgrass stands.
Different diseases develop under different environmental conditions and therefore are active at different times of the year in a given location. Fungicides can be applied preventatively to block fungi from infecting before they cause damage, or curatively to knock back an active and ongoing infection. There are multiple classes of fungicides that utilize different modes of action to reduce the viability and growth of the fungus. Given the wide range of diseases that can infect turf, and their interaction with environmental conditions and the host turf species or cultivar, it is easy to see why developing and executing an effective disease control program is one of the most important and challenging aspects of working as a golf course superintendent.
An effective disease management program is unique to a given site because each site has unique factors that affect the likelihood of fungal disease pressure. Effective programs consider the host turfgrass plant’s susceptibility to infection. For example, newer cultivars of creeping bentgrass are more resistant to dollar spot infection compared to older cultivars.
Being flexible and adaptable to constantly changing environmental conditions is also essential to effective disease management programs. If the weather forecast suggests disease pressure will be high, irrigation and dew reduction can be employed as cultural practices to reduce relative humidity in the turf canopy. Finally, effective programs with fungicide applications will rotate modes of action and utilize fungicides best suited to control the disease active at a given time of year.
When using fungicides to control pathogens, it is critical that the applications make it to the target and stay on the target once they arrive. Optimizing an application includes a number of factors, including choosing the correct spray carrier volume, nozzles, and tank-mix partners. Adjuvants are a useful tool to optimize applications and increase the likelihood that the fungicide achieves its goal by helping the application reach its full potential.
Drift reduction agents keep spray applications on target by fostering a more uniform and consistent spray pattern with less influence from environmental factors. Drift reduction agents “Right Size” the spray droplets leading to a reduced drift potential. Right sizing means that these formulations significantly reduce the amount of driftable fine droplets, while preventing droplets from becoming too large and bouncing off of a leaf surface. This keeps the fungicide in the application area and on the leaf for optimal protection.
A quality surfactant allows the fungicide to spread over the target area ensuring that the active ingredient will come in good contact with the target. This enables the active to do its work no matter what type of functional category the fungicide falls into. If the spray application does not adequately cover the leaf, the results of a fungicide treatment may not be as effective.
Multifunctional adjuvants offer convenience and ease of use by combining multiple functionalities in one adjuvant. For example, Exacto’s NIS/DRA is a multifunctional adjuvant with nonionic surfactant, deposition, and penetrant capabilities. When added to a tank mix with fungicides, it is proven to increase the droplet size of a spray mixture and reduce the amount of drift (Figure 1).
Figure 1: Exacto’s NIS/DRA drift reduction capabilities tested in a Battelle Wind Tunnel study. The study used an XR11003 nozzle at 40 psi. The results showed that adding NIS/DRA to the fungicide tank mix, droplet size increased and the percentage of driftable particles reduced.
Optimizing an application gives the fungicide the best chance to control disease and keep the turf healthy. In a study at the University of Wisconsin Madison, disease pressure from Dollar Spot (Sclerotinia homoeocarpa) was very high, as indicated by a high “area under disease” in Figure 2. Using the fungicide Daconil Ultrex reduced the amount of Dollar Spot as shown by the lower area under the dollar spot instance chart. Adding NIS/DRA to Daconil Ultrex further reduced Dollar Spot compared to the fungicide alone. The treatments with the best disease control had the highest “chlorophyll index,” related to the plant’s green color. In this study, among these treatments, the optimized treatment of Daconil Ultrex + NIS/DRA provided the best reduction in Dollar Spot and the best outcome for plant health.
Figure 2: Exacto’s NIS/DRA showed reduced dollar spot incidence and improved plant health in a University of Wisconsin Madison study. The increased chlorophyll index shows a greater amount of green in the turf.
Disease management is a complex challenge that must consider how host, pathogen, and environment interact to create disease problems. When fungicides are used in disease management programs, adjuvants are one tool to help optimize and get the most out of those applications.
Be sure to read the label of active ingredients to ensure essential adjuvants like surfactants, deposition aids, drift reduction agents, and spreader stickers are included or not prohibited for use in your fungicide tank mix.
Other useful information:
Fungicide Efficacy
Exacto Activator Adjuvants
Exacto Utility Adjuvants
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