Apple Disease Update: Week of June 8, 2025
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The forecast is calling for rain this week which means extended leaf wetting events and a battle to keep fungicide residues on the tree. We completed our first rating in our Glomerella leaf spot/bitter rot trials last week to give you early insight into what’s working so far. In addition to Captan 80WDG (2.5 lb/A) and Merivon, Omega has performing excellent in our ‘Gala’ block with high inoculum pressure. On Thursday June 5th we observed 23.7% incidence of GLS in the untreated program (no fungicides applied this year); whereas in the program where Omega was applied weekly since petal fall, we observed 6.8% incidence of GLS. Since we’ve tested Aprovia for many years and it’s been effective, we are not screening it this year. Given rainy week ahead combined with the early results from our GLS fungicide trial, I’d consider the following:
- If you applied Aprovia, a strobilurin (FRAC 11), or Omega last week with captan, consider applying 2.5 lb/A Captan 80WDG. You may want to add Topsin (thiophanate-methyl) for some added activity against GLS, frogeye leaf spot, Bot rots, and flyspeck/sooty blotch.
- If you DID NOT include a strobilurin (FRAC 11), Aprovia, or Omega last week, I’d suggest adding one of the aforementioned options in tank mixture with Captan 80 WDG (2.5 lb/A). Remember! Only 4 applications max of any FRAC 11, or any combinations of FRAC 11 fungicides. Also, Aprovia is limited to 3 applications of the high rate (7 floz/A) per season.
In addition to GLS and bitter rot, this is the earliest I’ve ever seen Marssonina leaf blotch on apple in NC. While rating the GLS trial last week, we observed quite a bit of MLB on ‘Gala’. For those who need a refresher here are some old photos from our ‘Rome Beauty’ block at MHCREC:
As of last week, the majority of symptoms I’ve observed resemble the bottom two photos. Unless you’ve had MLB issues in the past, applications of Captan 80WDG should do the trick. Neither Aprovia nor the single-A.I. strobilurins have performed well in our field trials. In addition to Captan 80WDG, which has good but not excellent efficacy, some of the better products for MLB control include:
- Cevya 5 floz/A (has label for MLB control)
- Tesaris (4.5 floz/A)- this is the active ingredient in Merivon so be careful about exceeding annual application limits for fluxapyroxad
- Inspire Super (12 floz/A)
- Cevya (5 floz/A) rotated with Howler Evo (2.5 lb/A)
- *All fungicide applications should be mixed with Captan 80WDG (2.5 lb/A)*. Other captan formulations can be considered.
Since we are reaching the robotic stage for apple disease management (Captan 80WDG + ………) let’s try something new for the upcoming weeks! In the feedback section, post any apple disease management questions you may have and I’ll address them in upcoming posts! Comments are anonymous!