Optimizing Fungicide Applications with Adjuvants

A uniform, healthy stand of turf is ideal for golf or sports fields, but it is also ideal for fungal diseases that infect the turf. Turf managers deal with 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 reduce disease infections 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 prevent 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.

The goal of fungicide applications is to get the chemical into or onto the leaf tissue and keep it there so that it can prevent fungal disease from getting in and taking over. If leaf tissue is removed or the fungicide degrades, disease can infect again. This makes reapplication essential to keeping disease away.

How Can Disease be Prevented?

Fungicide applications are imperative to prevent and reduce disease pressure. Every disease problem requires three factors for infection to occur 1. A suitable host (the turf) 2. The pathogen 3. An environment conducive to growth and infection by that pathogen.

These adjuvants are effective and reliable in aerial applications and are likely to support the performance of drone applications in modern agriculture. They are field-tested to ensure optimal performance under various conditions, providing a dependable and efficient solution for crop management.

When a susceptible host, pathogen, and environment meet, disease occurs.

Each site requires a unique disease management program that considers these factors and is flexible and adaptable to constantly changing environmental conditions. If the weather forecast suggests disease pressure will be high, irrigation and dew reduction can be employed to reduce relative humidity in the turf canopy. Repeated applications with different modes of action may also be necessary to control the disease. In fact, turf managers apply fungicides relatively frequently; 53% apply biweekly on greens while on fairways 36% apply biweekly and 38% apply monthly.¹

When tank mixing fungicides, there is a delicate balance in the way the chemical products are mixed and applied that can significantly impact their effectiveness. This is why following proper mixing order is essential to a successful application. Successful fungicide application is paramount to disease prevention.

Adjuvants – Technology for Fungicide Applications

Optimizing an application includes a number of factors, including choosing the correct spray carrier volume, nozzles, and tank-mix partners. With each fungicide application, the applications must make it to the target and stay on the target once they arrive to be successful.

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. Selecting the right adjuvants to get the fungicide active ingredient into the plant can make the application better.

Drift reduction agents (DRAs) 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.

Multifunctionals combine multiple functionalities in one adjuvant to create a convenient, easy–to–use product. For example, Exacto’s NIS/DRA is a multifunctional adjuvant with nonionic surfactant, deposition, and penetrant capabilities. When added to a fungicide tank mix, Exacto’s NIS/DRA 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 increased droplet size and decreased the percentage of driftable fine particles.

Including the right adjuvant in the tank 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 progress curve” in Figure 2. Using the fungicide Daconil Ultrex reduced the amount of dollar spot. 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, indicating improved plant health. Among these treatments, Daconil Ultrex + NIS/DRA provided the best reduction in dollar spot and the best outcome for plant health.

Figure 2: Exacto’s NIS/DRA 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 adjuvants like surfactants, deposition aids, drift reduction agents, and spreader stickers are recommended or not prohibited for use in your fungicide tank mix.

Resources:
1. Golf Course Industry Turf Report: Fungicides
Exacto Branded Adjuvants
Exacto Private Label Service
Exacto Turf and Ornamental

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Optimizing Fungicide Applications with Adjuvants