Early disease protection in apples
March 25, 2024
Green tip is just around the corner – in some orchards it’s already here!
With that brings the spring rush and the excitement of getting that sprayer into the orchard for early-season disease control. Not only does the sprayer need to be ready, but a plan for sustainably managing diseases like powdery mildew and apple scab should be in place.
With multiple fungicide applications made each year, rotating or mixing products with different FRAC codes helps delay fungicide resistance.
What are FRAC codes?
Every fungicide is classified by its mode of action. Each mode of action is assigned a number (single site mode of action fungicides) or letter-number combination (multi-site mode of action fungicides) called a FRAC code. These codes can be found on the front page of every product label in Canada.
Mix or alternate?
Mixing or alternating FRAC codes in a multi-spray program is a key strategy for resistance management. Both approaches help reduce the selection pressure that leads to field resistance.
Mixing modes of action helps ensure the implementation of a resistance management strategy. However, this strategy only works when mix partners have different FRAC codes, are both effective against the target disease, and sequential sprays of the same FRAC code are limited, making planning more complex.
Alternating modes of action provides flexibility in the rotation and helps limit the risk of overapplication of a specific FRAC code within a spray program.
Which products? Which codes?
Syngenta has four fungicides in the apple disease toolbox, each with varying levels of resistance risk:
| Product | Sequential sprays (#) | FRAC code | Resistance risk |
|---|
 | 2 | 3 + 9 | medium |
 | 2 | 7 | medium to high |
 | 2 | 3 + 7 | medium to high |
 | 1 | 29 | low |
Many scab fungicides contain Groups 3, 7 and/or 9. The general rule of thumb is to apply a code (group) no more than twice sequentially when targeting a disease with high-fungicide resistance risk like scab. For all fungicides, preventative applications are best. Curative applications of Group 3 and Group 9 fungicides should only be used in conjunction with an accurate disease forecasting system.
The total number of Group 7 applications in an apple program should also be limited and depends on if applications are made solo or in a mixture with an effective partner.
| Total # of sprays per crop | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
|---|
| Maximum Group 7 sprays (solo) | 2 | 2 | 2 | 2 | 2 | 3 | 3 | 3 |
| Maximum Group 7 sprays (mixture) | 2 | 3 | 3 | 3 | 3 | 3 | 3 | 4 |
What about low resistance risk fungicides?
Another key strategy for resistance management is the inclusion of low resistance risk fungicides in the spray program. Allegro® is a Group 29 fungicide classified as a low risk fungicide by FRAC.
New to using Allegro in apples?
- In Eastern Canada, consider Allegro for early apple scab protection, before powdery mildew is a risk.
- Allegro is a key component of a summer disease management program in many orchards. The liquid formulation is easy to mix and use.
- Check out the product details for more information.
Not just thinking about scab?
With fewer multi-site tools now available, disease spectrum matters. Check out the snapshot below to better understand which sprays have you covered.
| Product | L/ha | Control | Suppression |
|---|
| 0.56 to 0.84 | apple scab |
|
| 0.84 | Brooks fruit spot, cedar apple rust, flyspeck, quince rust, sooty blotch | powdery mildew |
| 0.3 to 0.5 | apple scab |
|
| 0.5 | powdery mildew, Alternaria blotch |
|
| 0.39 to 0.64 | apple scab |
|
| 0.64 | powdery mildew, Alternaria blotch, cedar apple rust, quince rust, Brooks fruit spot, sooty blotch, flyspeck |
|
| 0.5 to 1.0 | apple scab, flyspeck, sooty blotch |
|
| 0.75 to 1.0 | cedar apple rust, bitter rot, Alternaria rot | two-spotted spider mite, European red mite, apple rust mite |
| 1.0 |
| black rot, Brooks fruit spot, quince rust |
Curious about how these products might fit into your program? Reach out to your local rep to grab a Quick Reference Guide for apples.
For more information including articles, resources and videos on resistance management, check out Manage Resistance Now. This is a collaborative effort of industry, academia and government experts, brought together by CropLife Canada, to raise awareness and promote the adoption of strategies to manage weed, insect and disease resistance.
Always read and follow label directions. Allegro®, Aprovia®, Inspire® and the Syngenta logo are trademarks of a Syngenta Group Company. Allegro® is a trademark of ISK Biosciences Corporation
