Vineyard Pesticide Resistance Rotation Planner

By VitiScribe Editorial·August 1, 2025·Updated September 6, 2025

QoI fungicide resistance in powdery mildew is widespread in California vineyards. It didn't happen overnight, it's the result of years of heavy reliance on a single FRAC group (Group 11) without adequate rotation. That's what pesticide resistance looks like in practice: a class of chemistry that worked well stops working, often in the middle of a season when you need it most.

VitiScribe tracks FRAC and IRAC groups across all spray records for resistance management. This planner explains how FRAC/IRAC rotation works, which groups are at highest risk, and how to build a rotation that protects your program long-term.

TL;DR

QoI (FRAC Group 11) resistance in powdery mildew is already widespread in California -- programs that haven't rotated away from strobilurins are managing a resistant population, and increased application rates won't recover efficacy once resistance is established
Botrytis resistance to FRAC Group 1 (benzimidazoles) and FRAC Group 9 (anilinopyrimidines) is well-documented in commercial vineyards -- pre-harvest botrytis programs that rely on either group without rotation should be evaluated for efficacy history
The most common rotation failure is a plan made in January that isn't tracked through August -- a FRAC rotation on paper that shows proper diversity can still result in Group 11 overuse if group tracking stops during the busy summer season
No more than 2 consecutive applications from the same FRAC group and no more than 2-3 total applications from any single FRAC group per season are the practical rotation thresholds that resistance management programs build around
Multi-site materials (FRAC M) -- sulfur, copper, captan, mancozeb -- have very low resistance risk because mutations at multiple target sites are required simultaneously; these are the rotation anchors that should appear between every 1-2 applications of site-specific materials
IRAC rotation follows the same principle as FRAC: IRAC Group 28 diamide resistance has been confirmed in grape berry moth populations in some eastern US regions where chlorantraniliprole has been applied heavily without rotation

What Is FRAC Group Rotation and Why Does It Matter for Vineyards?

FRAC stands for Fungicide Resistance Action Committee. The FRAC system classifies fungicides by their mode of action, how they kill or inhibit fungi. Materials within the same FRAC group work the same way, which means fungi that develop resistance to one product in a group are typically resistant to all products in that group.

The principle behind FRAC rotation: if you alternate between different FRAC groups, resistance to one group doesn't eliminate your entire program. You're never selecting exclusively for resistance to a single mode of action.

This matters for vineyard managers because powdery mildew, botrytis, and downy mildew are all capable of developing fungicide resistance under selection pressure. QoI (FRAC 11) resistance in powdery mildew is already widespread. Botrytis resistance to FRAC 1 (benzimidazoles) and FRAC 9 (anilinopyrimidines) is well-documented in commercial vineyards.

For the full FRAC group breakdown by disease target and resistance risk, see the fungicide FRAC groups vineyard guide.

IRAC Rotation: The Same Principle for Insecticides

IRAC stands for Insecticide Resistance Action Committee. The same rotation logic applies to insecticides. Repeated use of the same IRAC group for grape berry moth or leafhoppers can drive resistance in local pest populations.

Key IRAC groups used in vineyards:

IRAC 1B (organophosphates): Phosmet, chlorpyrifos (where still registered)
IRAC 3A (pyrethroids): Bifenthrin, esfenvalerate, note: pyrethroids can cause mite flares
IRAC 5 (spinosyns): Spinosad, widely used for grape berry moth; lower resistance risk but rotate
IRAC 28 (diamides): Chlorantraniliprole, cyantraniliprole, effective for moth larvae; excellent safety profile

For the full IRAC group framework and resistance management for vineyard insect programs, see the vineyard insecticide IRAC groups guide.

Key FRAC Groups Used in Vineyard Programs

Powdery Mildew

|---|---|---|---|

Botrytis

|---|---|---|---|

| M | Multi-site | Captan | Low |

Downy Mildew

|---|---|---|---|

| M | Multi-site | Copper, mancozeb | Low |

How to Build a Resistance-Smart Rotation

Step 1: List your materials. Write out every fungicide or insecticide you're currently using in your vineyard program. Look up the FRAC or IRAC group for each.

Step 2: Map your seasonal applications. For each application in your season, record which FRAC/IRAC group was used. Are you applying the same group more than twice in sequence? That's a resistance risk.

Step 3: Identify problem sequences. The most common rotation mistakes:

Using a QoI (FRAC 11) product every other application because it's effective early-season
Applying the same botrytis material (e.g., fenhexamid) every pre-harvest application
Using the same insecticide group for all leafhopper applications through summer

Step 4: Build in FRAC/IRAC diversity. As a rule of thumb:

No more than 2 consecutive applications from the same FRAC group
No more than 2-3 total applications from any single FRAC group per season
Always rotate high-resistance-risk groups with lower-risk materials (including multi-site FRAC M materials)

Step 5: Track it through the season. This is where many rotation plans fall apart, the plan is made in January but not tracked through August. VitiScribe tracks FRAC and IRAC groups in every spray record, so you can see your rotation history in real time and catch repeated-group situations before they become a problem.

For your powdery mildew resistance management program specifically, see the powdery mildew resistance management guide. For your broader IPM program, see the complete vineyard IPM guide.

FAQ

What is FRAC group rotation and why does it matter for vineyards?

FRAC (Fungicide Resistance Action Committee) groups classify fungicides by their mode of action, how they kill fungi. Fungi that develop resistance to one product in a group are typically resistant to all products in that group. Rotating between different FRAC groups means that resistance to one group doesn't compromise your entire program. QoI resistance (FRAC 11) is now widespread in California powdery mildew populations, a direct result of heavy, unrotated use of strobilurin fungicides.

How do I build a resistance management rotation for vineyard fungicides?

List all the fungicides in your program and their FRAC groups. Map out your seasonal applications and check for consecutive applications within the same FRAC group (more than 2 in a row is high risk). Identify alternatives from different FRAC groups for each disease target, and plan your seasonal rotation before the season starts. Limit any single FRAC group to 2-3 applications per season and always include multi-site FRAC M materials (sulfur, copper) as rotation anchors with very low resistance risk.

Does VitiScribe track FRAC groups in spray records automatically?

Yes. VitiScribe tracks FRAC and IRAC group designations for every pesticide product logged in a spray record. When you add a product to a spray log entry, VitiScribe automatically records the FRAC or IRAC group from its product database. You can view your current season's FRAC group usage by block to see whether any group is being applied too frequently, and your rotation history is available across seasons for long-term resistance management planning.