We had what I would call a severe fire blight season, I pruned a lot of wood. Now after days of extreme heat warnings with excessive humidity.
What is this?
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My guess, Bitter rot. I could be wrong but it is some kind of summer rot on apples.
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Probably fungal (all the humidity helps it grow) you can look at pics of white rot, black rot, bitter rot, scab etc.
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Is there a way to get a positive ID of what’s going on here, I need to get whatever this is under control. What’s the sense in growing apples if they can’t be eaten?
Can try bringing to your local extension office. They often
Looks like Bitter Rot to me.
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I have no idea where that is at in southern Illinois. Maybe you know?
Good info here Apple Diseases - Fruit Rots, Control at Apple Harvest (and Postharvest)
Fungicides mentioned are fairly expensive but very little is used per gallon of water so not really its just they dont come in smaller quantities. Maybe there will be a group buy of Merivon or Pristine or Luna Sensation?
I emailed SIU Southern Illinois University Extension office maybe they can point me in the right direction. Thanks for you’re reply.
usually its a county by county office run by some university, so they should be able to direct you! ITs an excellent resource and mine does soil tests and diagnosis of disease.
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From my perspective, those are for commercial operations. Captan is great for peaches and works well for many apple issues. Mancozeb is a must for Tomatoes and is also very useful for apples. Mancozeb wettable powder is very affordable and Captan isn’t expensive either.
The Golden Ds are extreme rotters if not sprayed here in the humid SE, and Immunox, Captan, Mancozeb will take care of my needs. I never combine. For years I just used Captan but noticed CAR infected leaves are prone to Apple blotch. I recently started treating my trees with Immunox as directed.
I used immunox and captan plus indar. When my Immunox is gone I’ll go with eagle 20 instead.
Working on a table for apples - thought I would post for comments.
| Fungicide (Active Ingredient) | FRAC Group | Typical Rate (per acre) | PHI (Days) | Efficacy vs. Bitter Rot | Est. Cost/Acre | Notes |
|---|---|---|---|---|---|---|
| Omega 500F (Fluazinam) | 29 | 13.8 fl oz (high rate) | 28 | Excellent (at high rate) | $37 | Contact protectant; must use highest rate for bitter rot. Not for late season. |
| Merivon (Pyraclostrobin + Fluxapyroxad) | 7 + 11 | 5.5 – 8 fl oz | 0 | Excellent | $41 – $60 | Systemic; 0-day PHI makes it ideal for late season. Max 4 apps/season. |
| Pristine (Pyraclostrobin + Boscalid) | 7 + 11 | 10.5 – 14.5 oz | 0 | Excellent | $45 – $65 | Similar to Merivon; strong postharvest rot suppression. Max 4 apps/season. |
| Luna Sensation (Fluopyram + Trifloxystrobin) | 7 + 11 | 5.0 – 7.6 fl oz | 14 | Excellent | $35 – $50 | Good for mid-season; 14-day PHI restricts use near harvest. |
| Aprovia (Benzovindiflupyr) | 7 | 10.5 – 13.5 fl oz | 30 | Very Good | $30 – $45 | Strong early-mid season option. Long PHI (30 days). |
| Flint Extra (Trifloxystrobin) | 11 | 2.0 – 3.8 oz | 14 | Very Good | $25 – $35 | Strobilurin only; resistance risk. Tank-mix required. |
| Fontelis (Penthiopyrad) | 7 | 20 fl oz | 14 | Good (with Captan) | $30 – $40 | Fair alone; must tank-mix with Captan for efficacy. |
| Captan (Captan) | Multi-site | 3.0 lbs (80% WDG) | 0 | Good/Very Good | $15 – $20 | Broad-spectrum protectant. Essential tank-mix partner. Low resistance risk. |
| Ziram (Ziram) | Multi-site | 4.0 lbs | 14 | Good | $20 – $25 | Broad-spectrum; alternative to Captan. |
| Mancozeb (Mancozeb) | Multi-site | 3.0 – 4.0 lbs | 77 | Good | $15 – $25 | Early season only due to long PHI. Excellent for scab/rot complex. |
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How often did you spray?
I have a comment. You have a tree problem. Top work the tree and graft on a better disease resistant varieties.
What variety is it?
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That was my issue… during the “heat dome” I thought we became Florida. It rained some everyday for almost 2 weeks. That and the fog overnight it might as well have rained.
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Best I can tell… no variety of apple is resistant to bitter rot. If you find one please let me know. I have about 20 varieties currently. Every variety that set apples got this rot. I was hoping to offer scions this coming spring but no way with this rot business gone crazy would I.
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A quality spreader/sticker can help your fungicides make it through rainy periods more effectively
I have been using southern ag spreader sticker Spreader Sticker - Southern Agricultural Insecticides, Inc. I like it but it’s the only one I’ve ever used, so nothing to compare it with. Cherries and peaches did well with my tank mixed sprays. Apples and pears - wow almost a total loss. I need to get a handle on this rot business for next season.
From what I have read, Mancozeb is pretty effective, but it has a 66 day pre harvest limit. That limitation was added later in the product life cycle for Mancozeb, and some people have argued that Bitter Rot has since become more of a problem. I plan to use Mancozeb as an early spray next year, following up with Merivon and Fluazinam, rotating, both combined with captan. Switching between Merivon and Fluazinam, to avoid selecting for resistance (Frac group 11 and 29 respectively), and adding Captan also to make resistance harder. Mancozeb hits many fungal targets ,so resistance development is not a concern. Bitter Rot is caused by many different species of the genus Colletotrichum, and they don’t have the same susceptibility to narrow target fungicides like Merivon. I figure that prolonged single use of such a fungicide can also cause a shift of species in your orchard towards more resistant species, rather than resistance mutations in a given species. Dormant sprays with copper and sulfur are probably also a good idea, to knock down overwintering fungal spores in the tree. Just a summary of what I have read.
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