6/10/2025 - By Kyle Creamer

As we are now right at the beginning of summer, pest and disease pressure is beginning to ramp up in greenhouses and nurseries across the country. Now is the time to take preventative action and get a head start on treating plants before conditions become more favorable. Greater humidity, warmer temperatures, strong winds and an occasional rainstorm make ideal conditions to spread pathogens that infect plants and cause disease.

In this article, we will discuss a few prevention options and how you can tank mix them for powerful rotations, providing your nursery or greenhouse with powerful protection.

Products and Spray Programs for Disease Management

One highly effective approach to managing foliar diseases is tank mixing contact fungicides (i.e., Chlorothalonil, Mancozeb, copper) with acropetal penetrating fungicides (distribute systemically toward leaf tips in the xylem) such as some of the strobilurin, succinate dehydrogenase inhibitors (SDHIs), and demethylation inhibitors (DMIs). This approach protects plant tissue from becoming infected and suppresses the development of existing infections.

Here is an example of a spray program that offers broad-spectrum disease control:

1. Orkestra® intrinsic fungicide (broad-spectrum systemic fungicide) 10 oz. per 100 gallons, tank mixed with 20 oz. per 100 gallons of Harrell’s ProtectMAX® Mancozeb (contact fungicide- Mancozeb with no sticker surfactant) OR 24 oz. per 100 gallons of Harrell’s ProtectMAX® Chlorothalonil 6L (contact fungicide- Chlorothalonil with no sticker surfactant) – (FRAC 11/7 & M3 or M5) 14 days later, ROTATE WITH
2. Avelyo® fungicide (broad-spectrum systemic fungicide) 8 oz. per 100 gallons, tank mixed with 20 oz. per 100 gallons of Harrell's ProtectMAX® Mancozeb OR 24 oz. per 100 gallons of Harrell’s ProtectMAX® Chlorothalonil 6L - (FRAC 3 & M3 or M5) 14 days later, ROTATE WITH
3. Harrell's ProtectMAX® T-Methyl Fungicide (broad-spectrum systemic fungicide) 16 oz. per 100 gallons, tank mixed with 20 oz. per 100 gallons of Harrell's ProtectMAX® Mancozeb OR 24 oz. per 100 gallons of Harrell’s ProtectMAX® Chlorothalonil 6L -(FRAC 1 & M3 OR M5) 14 days later, REPEAT the rotation

Surfactant for Foliar Applications with Broad-Spectrum Disease Control Tank Mix

To improve coverage on the leaf tissue, add a wetter/spreader type surfactant such as Harrell’s HydroMAX® Fleet® 100 Harrell's HydroMAX® Fleet® 100at 16 oz. per 100 gallons. Wetter-spreader surfactants like Fleet® 100 will flatten the water droplet and spread the product evenly over the leaf tissue, providing excellent coverage. This is beneficial for spreading the active ingredient over fungal pathogens on the leaf surface (i.e., mildews, rust, etc.), increasing activity and disease control.

Build the Perfect Disease Management Program for Your Operation

With how important it is to make sure your disease management program is effective, building it out is one headache you don’t need. Connect with us and allow your local Harrell's Rep to help you put together exactly what your plants need this season and all throughout the year. Find your Rep here to get started and we’ll talk to you soon.