Thorough scouting along with appropriate cultural practices and effective rotation programs can reduce the threat of crop loss by downy mildew and Phytophthora spp. pathogens. Recognizing the early signs is critical to plant quality and health. Most downy mildew and Phytophthora fungi prefer cooler temperatures (between 50 - 75°F), wet conditions and relative humidity levels of 85% or greater. During these conditions, a preventive fungicide program is recommended to protect susceptible crops from diseases that can affect the quality and future sale of the plants.

The systemic activity of Segovis^® and Subdue Maxx^® fungicides provide excellent protection against downy mildew and Phytophthora on rose crops. With different modes of action, these products can serve as the framework for a resistance management and rotation program.

Segovis and Subdue Maxx knock out downy mildew
Tennessee State University completed trials in 2016 with Segovis and Subdue Maxx on Knockout^® roses. Trial 1 evaluated the systemic protection of Segovis and Subdue Maxx when applied as a drench to protect the roses from downy mildew.

• Treatments of Segovis and Subdue Maxx significantly reduced disease severity compared to the non-treated control.
• All fungicide treatments significantly improved plant health and increased the average plant height compared to non-treated control.

Control of downy mildew on roses – drench
Trial 1

• Drench treatment: Applied June 22
• Severity of downy mildew was evaluated on June 29, July 6, July 14 and July 22 using a scale of 0-100% foliage affected
• Rose plants were rated for downy mildew by counting the total number of infected leaves per plant on July 22
• No phytotoxicity, defoliation or visual residue was observed in any of the rose plants

Knock-out downy mildew with a complete rotation program
Because downy mildew is such a devastating disease and can infect a wide array of woody and herbaceous ornamentals, Syngenta developed a rotation program for growers that feature some of the best fungicides with different modes of action. These agronomic programs are applicable for ornamental crops grown in greenhouses or nurseries and they have been researched to confirm their performance.

In 2016, Tennessee State University also conducted trials on Knockout roses using our downy mildew rotation solution comprised of Subdue Maxx, Segovis, Mural^® and Micora^® fungicides. In this trial (Trial 2), the strength of the rotation was tested on a 7 and 14-day interval.

• The downy mildew fungicide rotation programs significantly reduced downy mildew incidence and the average number of infected leaves compared to non-treated control
• There were no differences between plants treated on the 7-day versus the 14-day schedule in downy mildew incidence and average number of infected leaves
• The fungicide rotation program on the 7-day schedule significantly increased measured plant height compared to non-treated control

• Rotation treatments were applied with CapSil^® at 4 fl oz/100 gal beginning on Aug. 12 and ending on Oct. 21 for a total of six applications on a 7-day and 14-day schedule
• Rose plants were rated for downy mildew by counting the total number of infected leaves per plant on Oct. 28
• Plant average width and height were measured on Oct. 28
• Phytotoxicity, defoliation and visual residue data were evaluated on Aug. 19, Aug. 24, Sept. 2, Sept. 9, Sept. 16, Sept. 23, Sept. 30, Oct. 7, Oct. 14, Oct. 21, and Oct. 28 using a scale of 0-100% foliage affected
• No phytotoxicity, defoliation or visual residue was observed in any of the rose plants

Learn more about Segovis at GreenCastOnline.com/Segovis.

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