Viticulture

Introducing KEYBRI® Ultra fungicide: A new standard in downy mildew protection for grapes
Incidence and severity of downy mildew (Plasmopara viticola) on grapevine leaves and bunches (cv. Chardonnay) following two applications at E-L 16 & E-L 18 (21-day interval).

Consistency is key when keeping downy mildew out of grape crops. This makes KEYBRI® Ultra a powerful choice in unpredictable seasons.

"KEYBRI® Ultra offers a new standard in protection," Syngenta Technical Services Lead Len Ibbotson said. "It combines two specialist downy mildew fungicides. Growers can count on it to target the key stages of disease development during initial infection and early-stage establishment."

"This protection is quickly established and is long lasting. This is crucial when conditions can delay fungicide applications."

KEYBRI® Ultra fungicide highlights

  • Effective downy mildew control: KEYBRI® Ultra fungicide provides robust protection against downy mildew. It helps grape growers safeguard their crops from this destructive disease.
  • Complete formulation: KEYBRI® Ultra fungicide incorporates two specialist downy mildew fungicides and an adjuvant package. It has built-in resistance management. No need to add additional products to the tank.
  • Extended residual activity: KEYBRI® Ultra fungicide has long-lasting residual activity up to 21 days. This ensures prolonged defense. It reduces the need for frequent applications and provides peace of mind for growers.
  • Rainfastness: This fungicide's exceptional rainfastness ensures it remains effective even after exposure to rainfall. It offers reliable protection under varying weather conditions.
  • Enhanced formulation: KEYBRI® Ultra fungicide's advanced formulation maximises spreading and uptake. This optimises its efficacy and ensures comprehensive protection for grapevines.

Strong control and extended residual activity

KEYBRI® Ultra is a fully-loaded and optimised formulation. It streamlines spray applications. Complete with in-built adjuvant, KEYBRI® Ultra contains:

  • Oxathiapiprolin: A potent oomycete fungicide that inhibits downy mildew development at extremely low concentrations
  • Proven mandipropamid (Group 40)

This makes KEYBRI® Ultra a robust option. It gives growers a welcome alternative to copper mixes.

In Australia, the performance, crop safety and physical compatibility of KEYBRI® Ultra were evaluated over several seasons. Testing occurred in different locations with multiple cultivars.

During the development studies in Australia, KEYBRI® Ultra performed exceptionally well. It was comparable with existing standards, including REVUS® fungicide when treatments were applied at a 10-14 day spray interval.

However, when the spray interval was extended to 21 days, trial results suggested that KEYBRI® Ultra may offer superior performance. It provided extended residual control of downy mildew, compared to REVUS® fungicide (Figure 1).

Incidence of downy mildew (Plasmopara viticola) on grapevine bunches (cv. Merlot) following multiple applications of KEYBRI Ultra and REVUS applied at 10-14 (6-spray program) or 21-day intervals (3-spray program) from E-L 12 (5 leaves separated) to E-L 31 (pea sized).
Figure 1: Incidence of downy mildew (Plasmopara viticola) on grapevine bunches (cv. Merlot) following multiple applications (for research purposes), applied at 10-14 (6-spray program) or 21-day intervals (3-spray program) from E-L 12 (5 leaves separated) to E-L 31 (pea sized). Disease assessments conducted at 11 and 34, or 23 and 46 days after application (DAA) six or three respectively. Columns with the same letter for each assessment timing are not significantly different (P<0.05). Coldstream, Vic 2021-2022. Syngenta trial ID FSF062A4-2021AU.

Len said that protecting the fruit against disease is paramount. He also noted the value in protecting vegetative growth.

"Left unchecked, downy mildew infections can cause significant damage to the grapevine canopy," Len said. "There is potential for a complete loss of leaves during the growing season. Premature defoliation not only reduces ripening capacity in the current season. It can lead to a reduction of carbohydrate reserves and vine performance for the subsequent season."

In multiple studies carried out in Australia, KEYBRI® Ultra consistently reduced defoliation of vines affected with downy mildew (Figure 2).

Percent leaf drop (cv. Chardonnay, Shiraz and Merlot). Average of five trials, Vic and Qld, 2016-17 and 2020-21. Assessments made 22-65 days after final application.
Figure 2: Percent leaf drop (cv. Chardonnay, Shiraz and Merlot). Average of five trials, Vic and Qld, 2016-17 and 2020-21. Assessments made 22-65 days after final application. Untreated defoliation ranged from 13 – 95%.

During the 2023-2024 growing season, KEYBRI® Ultra fungicide was evaluated under commercial application conditions in Victoria's Yarra Valley. It used the maximum of two applications, strategically timed to align with possible infection windows.

KEYBRI® Ultra was compared to:

  • Untreated vines (which received no early season downy mildew treatments)
  • A copper treatment (Blue Shield* DF)

Fortnightly copper cover sprays were applied to both treated and untreated vines from early December through to veraison. This was in response to wet conditions that persisted throughout December.

Len noted that KEYBRI® Ultra performed exceptionally well considering the very lean downy mildew program. A low and commercially acceptable level of disease was noted on vines and bunches when assessed in February (Figure 3).

KEYBRI® Ultra vines appeared overall healthy. The full impact of downy mildew was clear on untreated vines, with significant canopy deterioration and almost no crop (Figure 4).

Throughout the development studies, KEYBRI® Ultra was also found to be safe to grapevines. It was highly compatible with a range of potential tank mix partners.

Incidence and severity of downy mildew (Plasmopara viticola) on grapevine leaves and bunches (cv. Chardonnay) following two applications at E-L 16 & E-L 18 (21-day interval).
Figure 3: Incidence and severity of downy mildew (Plasmopara viticola) on grapevine leaves and bunches (cv. Chardonnay) following two applications at E-L 16 & E-L 18 (21-day interval). Disease assessed 110 days after application two. Columns with the same letter for each assessment type are not significantly different (P<0.05). Research solutions, Coldstream, Vic. 2023-24.
Incidence and severity of downy mildew (Plasmopara viticola) on grapevine leaves and bunches (cv. Chardonnay) following two applications at E-L 16 & E-L 18 (21-day interval).

Outstanding performance under wet conditions

KEYBRI® Ultra fungicide is locally systemic with limited acropetal xylem mobility. Both active ingredients bind strongly to the waxy cuticle layer. They are then absorbed through leaves or berry caps. This offers protection to the underside of these tissues (translaminar movement).

Oxathiapiprolin is also translocated gradually outwards through the xylem.

"This combination of strong binding, translaminar movement and gradual translocation are what give KEYBRI® Ultra fungicide its excellent rainfastness and residual disease control properties," Len said.

The rainfastness properties of KEYBRI® Ultra were evaluated in several studies. There was no drop in performance even when up to 60 mm of rainfall was applied one hour after application (Figure 5).

Performance of KEYBRI® Ultra before and after simulated rainfall.
Figure 5 Performance of KEYBRI® Ultra before and after simulated rainfall. Vines (cv. Roter Gutedel) were inoculated with Plasmopara viticola one day after application. All products applied at the label rate in 250 L water/ha at E-L 31 (berries pea sized). 60mm of rain was applied one hour after application. Treatment efficacy was calculated by comparing the disease presence on leaves and berries with the untreated check, 28 days after inoculation. (2019.4049.1;2019-020).

Rainfastness is a critical quality of a good downy mildew fungicide. Disease pressure increases during wet periods. The best control is achieved when fungicides are applied before rain and subsequent infection periods.

Growers can be confident that KEYBRI® Ultra will continue to offer strong protection. It controls downy mildew even during challenging conditions where access to vineyards for post infection sprays may not be possible.

Conclusion

"KEYBRI® Ultra fungicide represents a significant milestone in the fight against downy mildew in grapes," Len said. "It offers growers a reliable and effective solution for disease management. With its powerful formulation, extended protection, and exceptional rainfastness, this fungicide is poised to make a substantial impact for downy mildew management in wine grapes. It supports healthier vineyards and higher-quality yields."

Click here for more information or contact your local Syngenta representative.

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