Botrytis Spray Log: Documenting a Bunch Rot Management Program in Your Vineyard

By VitiScribe Editorial·March 22, 2025·Updated June 8, 2025

Botrytis bunch rot is responsible for 15-30% yield loss in susceptible California vineyard blocks in wet vintages. That's a real number with real financial consequences. The spray program you run to prevent it, and the records you keep about that program, both matter.

TL;DR

Botrytis spray logs require FRAC group notation for every application -- consecutive same-group applications create resistance pressure that eventually causes program failure
Switch (FRAC Groups 12 + 7) used as the only botrytis product means you're applying the same mode combination every time, which most resistance guidelines say should not exceed two consecutive applications
Most primary botrytis fungicides carry a 7-day PHI in California grapes -- for a September 1 Chardonnay harvest, the last compliant application window is August 25
Canopy management records (leaf removal date, shoot thinning) belong on the same block timeline as botrytis spray records to show an integrated management approach
Documenting the vine growth stage at each botrytis application shows that timing was phenologically appropriate rather than calendar-based
Botrytis bunch rot is responsible for 15-30% yield loss in susceptible California blocks in wet vintages -- thorough records both protect the crop and document the program when losses occur

Botrytis spray logs have specific documentation requirements that generic spray record templates often miss: FRAC group rotation tracking, canopy management integration, and PHI management for multiple products with different harvest restriction windows.

What Makes Botrytis Record-Keeping Different

Multiple Products with Different FRAC Groups

Botrytis resistance management requires rotating between FRAC groups. Botrytis cinerea has demonstrated resistance to multiple fungicide classes across California wine regions, and any single FRAC group used exclusively for more than one or two consecutive applications in a season creates selection pressure for resistance.

The FRAC groups most commonly used for botrytis in California vineyards:

FRAC group 12: Cyprodinil (Vangard, component of Switch). Effective and widely used.
FRAC group 7: Fludioxonil (component of Switch), boscalid (component of Pristine, Endura). SDHIs with botrytis activity.
FRAC group 2: Iprodione (Rovral). Historically effective, now with resistance concerns.
FRAC group 17: Fenhexamid (Elevate). Effective, particularly at harvest timing.
FRAC group 3: Some DMIs have limited botrytis activity as secondary targets.
FRAC group M: Multi-site materials (captan, fludioxonil in some formulations) with resistance management benefits.

Using Switch (cyprodinil + fludioxonil) as your primary and only botrytis product means you're using the same combination of groups 12 and 7 every time. Most resistance management guidelines recommend not using the same FRAC combination more than twice consecutively. Your spray log should show that rotation is happening.

VitiScribe's FRAC tracking flags overuse of a single resistance group automatically. When your botrytis spray log shows three consecutive applications of the same FRAC combination on any block, the system alerts you before the fourth application rather than after you've already made the rotation error.

PHI Differences Between Botrytis Products

The botrytis fungicides have different PHIs that create real planning complexity:

Switch (cyprodinil/fludioxonil): 7 days
Pristine (boscalid/pyraclostrobin): 7 days
Elevate (fenhexamid): 7 days
Rovral (iprodione): 7 days in some registrations
Captan 80W: 0 days (verify current label)

The 7-day PHI on most primary botrytis fungicides gives you good flexibility. The practical issue is that if you're running multiple applications close to harvest, the last application that's within PHI must still clear before the earliest-picked fruit.

For Chardonnay harvesting September 1st, a botrytide application must be complete by August 25th if the PHI is 7 days. If disease pressure forces an application on August 27th, you need a product with shorter PHI, or you need to acknowledge that Block 2 Chardonnay won't harvest until September 3rd.

Canopy Management Integration

Canopy management reduces botrytis risk directly. Proper leaf removal at fruit zone can reduce botrytis incidence by 40-60% in susceptible varieties by improving airflow and spray penetration.

Botrytis spray records are more defensible and more interpretable when canopy management records appear on the same block timeline. A block with documented fruit zone leaf removal before bloom shows a grower who's managing botrytis proactively, not just reactively. A block with high spray application counts but no canopy management records raises the question of whether the spray program is compensating for inadequate cultural management.

VitiScribe's botrytis spray records link canopy management notes that connect disease pressure to vine architecture. When you log a pre-bloom leaf removal event for a block, that record appears on the same timeline as the botrytis fungicide applications for that block, creating the integrated IPM narrative.

Season Timing Documentation

Botrytis spray timing documentation should capture the relationship between application timing and vine growth stage:

Early bloom (BBCH 60-65): Infected flower caps are the initial infection source for botrytis bunch rot. An application at this timing, documented with the growth stage in the record, shows that bloom-window management was part of the program.

Bunch closure (BBCH 77): Last effective opportunity for spray penetration inside the cluster. Document the growth stage in the spray record to show the timing decision was phenologically appropriate.

Veraison (BBCH 83): Berry softening creates new infection risk. Document berry condition and any rain events preceding this application to justify the timing decision.

Pre-harvest: The last application within PHI before anticipated harvest. Documenting the anticipated harvest date alongside this record confirms that the PHI was considered in the timing decision.

What a Complete Botrytis Spray Log Looks Like

For a Chardonnay block with a botrytis program, a complete season's spray log should show:

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

| July 8 | Elevate WDG | 17 | 7d | Bunch closure | - |

| Aug 15 | Pristine | 7+11 | 7d | Veraison | Heavy fog week of Aug 10 |

| Aug 29 | Switch 62.5WG | 12+7 | 7d | Pre-harvest (harvest est. Sept 7) | - |

This log shows:

FRAC rotation: 12+7, 17, 7+11, 12+7. Not ideal on the consecutive group 7, but group 17 and multi-target elements break the sequence.
PHI compliance: Last application August 29, 7-day PHI clears September 5, harvest estimated September 7.
Growth stage documentation at each timing.
Weather note justifying the veraison application.
Canopy management integrated with program timing.

VitiScribe's botrytis management hub tracks the FRAC rotation for botrytis products specifically and flags consecutive use of the same group combination. The vineyard spray log software handles the full record-keeping structure.

Frequently Asked Questions

What spray records should I keep for a botrytis management program?

Complete botrytis spray records should include all standard DPR-required fields plus FRAC group identification for each product applied, vine growth stage at application timing, any weather events that influenced the timing decision, canopy management notes linking leaf removal and shoot thinning activities to the disease management timeline, and PHI calculations against anticipated harvest date for all pre-harvest applications. The records should show FRAC rotation across the season so resistance management can be verified.

How does VitiScribe track FRAC rotation to prevent botrytis resistance?

VitiScribe records the FRAC group for every product application automatically when you select a product from the database. The system tracks the sequence of FRAC groups applied to each block and alerts you when the same group or combination is used more than twice consecutively. This resistance tracking applies to botrytis-specific FRAC groups separately from the powdery mildew FRAC rotation tracking, recognizing that the two disease programs use overlapping products with distinct rotation requirements.

What are the PHI requirements for common botrytis fungicides in California?

Most primary botrytis fungicides registered for use in California grapes carry a 7-day PHI: Switch 62.5WG (cyprodinil + fludioxonil), Elevate WDG (fenhexamid), Pristine (boscalid + pyraclostrobin), and most iprodione formulations. Captan has a 0-day PHI in some registrations. PHI requirements should always be verified on the current product label before each application, as label revisions can change PHI requirements. VitiScribe pulls current PHI from registered label data and calculates clearance dates against your entered anticipated harvest date.

Should botrytis spray records include scouting observations that triggered each application?

Yes. Linking scouting observations to spray decisions is what distinguishes threshold-based IPM documentation from calendar-based spraying in the record. When a certifier or auditor reviews your botrytis spray log, they can see that each application was preceded by a scouting visit that documented the disease pressure or environmental conditions that justified it. A record that shows "spray applied, no observation noted" is defensible from a basic compliance standpoint but weak from an IPM standpoint. See block scouting template for the scouting fields that pair with botrytis spray records.

How does a botrytis spray log support a crop insurance claim after a wet vintage loss?

Documented botrytis spray records showing that your program was timely, well-timed by phenological stage, and rotated appropriately across FRAC groups provide evidence that you managed the crop reasonably. Crop insurance adjusters reviewing a bunch rot loss claim will want to see that applications were made during the critical bloom and pre-harvest windows and that PHI was observed. A complete spray log with weather notes, growth stage documentation, and canopy management integration supports your claim. Records showing no spray activity during key risk windows may be interpreted as evidence of inadequate management.

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Managing Spray Programs Across Multiple Varietals in One Vineyard

Sources

California Department of Pesticide Regulation (CDPR)
UC Cooperative Extension Viticulture
Wine Institute
American Vineyard Foundation
American Society for Enology and Viticulture (ASEV)

Get Started with VitiScribe

Botrytis spray records are more complex than basic pesticide compliance logs because they require FRAC rotation tracking, growth stage documentation, and PHI management against a moving harvest target. VitiScribe handles all of that automatically -- FRAC groups pull from the product library, PHI calculates against your block's harvest date, and canopy management events appear on the same timeline as fungicide applications. Try VitiScribe free and log your first botrytis application with FRAC rotation tracking built in.