I have a bad PLC fungal problem with about 30 peach & nectarines stonefruit in a damp location.
Copper spray and other oil/sulfer treatments have failed and I’m loosing young trees.
My research suggests Ziram and Chlorothalonil are most effective. I’m unable to find Ziram in small quantities, does anyone have a source for a pound? Or can suggest a similar effective dormant spray alternative that’s available in smaller quantities.
Isn’t chlorothalonil much more widely available.
CHAT check
are Chlorothalonil and Ziram equally affective at PLC control.
If by PLC you mean peach leaf curl (Taphrina deformans), then no—chlorothalonil and ziram are not equally effective, and in practice they should not be considered interchangeable.
Below is a precise, field-relevant comparison.
Effectiveness: Excellent / gold standard
Bottom line:
If applied at late fall leaf drop and/or late dormant (bud swell), chlorothalonil provides very high and repeatable control.
Effectiveness: Moderate at best
Bottom line:
Ziram can reduce disease pressure only when timing and coverage are excellent, but it does not provide equivalent control under real-world conditions.
Interesting, that seems contradictory to IPM for PLC citation below, and statements in Growing Fruit seemed to indicate Ziram. Am I missing something?
“Several other fungicides that are equivalent or even more effective than copper for managing peach leaf curl are ziram, chlorothalonil (Echo or Bravo), and dodine (Syllit) when applied at the optimal time. Ziram is most effective.”
Ref.
https://ipm.ucanr.edu/agriculture/nectarine/peach-leaf-curl/#gsc.tab=0
If for no other purpose than to demonstrate that all “AIs” don’t draw the same conclusions… Here’s what Google Gemini responds with for Alan’s question:
Both Chlorothalonil and Ziram are highly effective for Peach Leaf Curl (PLC) control, and both are considered superior to standard copper-based fungicides. However, they are not strictly “equal” in terms of performance or availability.
1. Effectiveness Comparison
- Ziram: Generally considered the “gold standard” for commercial growers. It is often ranked as the most effective single product for PLC, especially under high disease pressure. It is highly resistant to wash-off from rain and has a multi-site mode of action that prevents fungal resistance.
- Chlorothalonil (Bravo/Daconil): Also extremely effective and frequently ranked alongside or just slightly below Ziram. It has excellent “redistribution” properties, meaning that when it rains, the chemical moves slightly to cover new growth or areas that were missed, which is a major advantage during wet springs.
2. Key Differences in Use
Feature Chlorothalonil Ziram Availability Widely available for home gardeners (e.g., Daconil). Primarily a commercial product (Ziram 76DF); harder to find for home use. Timing Dormant only. Must stop at “leaf curl” or “shuck split” stage; can be toxic to young foliage. Dormant preferred, but some labels allow for “emergency” early-season use to slow a spread. Rain Resistance Excellent (redistributes with water). Superior (very high “stickiness”). Other Benefits Also controls Peach Scab and Brown Rot blossom blight. Also controls Shothole (Coryneum blight). 3. Application Strategy (2025–2026 Recommendations)
For the best results in the current season, university extension services suggest:
- The Single Spray: Apply either product in late fall (after 90% leaf drop) or early spring (before bud swell).
- The Double Spray: If your trees had a severe infection last year, apply a Ziram or Copper spray in the late fall, followed by a Chlorothalonil spray in the early spring before the buds turn green.
- The “Emergency” Window: If you miss the dormant window and buds are already swelling, Chlorothalonil and Ziram are both more effective than copper at providing “last minute” protection.
Safety Note
Ziram is a more powerful and potentially more hazardous chemical than consumer-grade Chlorothalonil. If you are a home gardener, Chlorothalonil (Daconil) is the safer, more accessible choice that will provide nearly identical results.
It is important to ask for research that has been done comparing the two fungicides side to side. Chat came up with what seems like misinfo because it was based on Bravo Weatherstick which theoretically would be superior to a back loaded sticker.
I seriously doubt there is meaningful difference between the efficacy of the two and I also believe the failure of copper may have been the result of poor timing. Copper works fine here for PLC, but pressure isn’t as bad as in parts ot the northwest.
All sales of Ziram are banned. Ferbam and Thiram not far behind.
Great dissertation! I’ll apply Chlorothalonil as soon as I can procure, as some buds are swelling already. It’s a challenge to get a dry enough day this time of year given my poor orchard site.
What is interesting to me is the fact that AI spits out different answers partially because the actual research is extremely limited. I don’t think a single study has been done to compare the two fungicides side by side, but when Bravo came out with a new patent that included a sticker in the formula it created noise about chloro itself being superior to Ziram When you follow the AI conclusions the mistakes are often the result of misleading assertions by researchers who tend to exaggerate the implications of their research for obvious reasons, whether it is conscious or not.
However, funding for research comparing products is very limited. Sometimes the best thing to do is ask what commercial orchardists are using in your own region. They cannot afford either overpaying for pesticides or crop failure. Collectively their methods are likely very reliable sources of info- probably much more so than university based guidelines which have incentives not to dispense the “truth” beyond a level that threatens crops.
That said, commercial orchards often face a much higher level of pest pressure than our own home orchards, both because they attract more pests and because they must produce a very high percentage of pristine apples that store very well. But both university guidelines and the modifications practiced by commercial growers are equally affected by this need for pristine and extra pest pressure.
I should add that for west coast growers, ziram is preferred and more reliable in single applications due to the extended risk of infection while humid region growers tend to prefer chlor because PLC is easier to control based on a shorter window of infection and because it is affective against many fungal pests for which ziram in not. Pests much more prevalent in the humid region than in the west.
I applied a 50/50 ratio of Ortho 29% chlorothalonil and Kocide 3000 (46% copper hydroxide) 30% elementry equivalent. Mixing products was suggested as acceptable. Applications were done at maximum recommend dose. So we’ll see how that works, I’ll report efficacy.
The old research always indicated chlorothalonil was more effective than Ziram for leaf curl.
The big reason I mostly used/use chlorthalonil here for leaf curl was/is cost. The costs are a little closer now between the two. Last year a 40 lb. bag of Ziram cost $190, or $23.75 per acre for leaf curl. Bravo cost $73 for 2.5 gal. or roughly $22.75 per acre (but there are generic chlorothalonil versions cheaper than Bravo). That doesn’t include shipping, which is expensive for both because both are considered class 9 hazmat, which incur significant up charges in shipping.
One other thing to be aware of is that Ziram has a “Danger” signal word, whereas Bravo just carries the “Caution” signal word. Not a huge deal. Captan 80 also carries a “Danger” signal word.
DF and WDG like Ziram and Captan 80 probably carry the “Danger” signal word because the powder, if inhaled, at those concentrations, isn’t so good for you. So you’ll need to make sure you hold your breath, while mixing, lol.
All joking aside, I did once get a little Captan 80 powder in my eye. Burned like %$&&. So one does need to be more careful with compounds with “Danger” on the label.
A lot of the old literature was based on east coast conditions. Apparently, Ziram is more affective in at least parts of the west because its chemistry sustains efficacy for a few more days. In the west, the infection period can be much more extended. Here, in the east, even copper usually does the trick. A single app.
Here is CHAT’s explanation.
Ziram
Is a dithiocarbamate fungicide.
It forms a relatively insoluble, rubbery film on the plant surface.
That film sticks better and washes off more slowly, so it persists through light rain and time.
It works by shutting down key enzyme systems in fungal spores on contact.
Chlorothalonil
Is a chlorinated aromatic compound.
It forms a more crystalline, brittle residue on the surface.
That residue breaks down and erodes faster from UV light and weathering.
It works by reacting with sulfur-containing proteins, but the protection layer doesn’t last as long.
Bottom line (why growers notice a difference):
Ziram’s chemistry leaves a more durable protective coating, while chlorothalonil leaves a harder but less persistent deposit.
It is puzzling that if Ziram sticks better, and is less effected by weather, why it wouldn’t also perform better than chlorothalonil in the east, as well as the west.
The only reason I can think of is that chlorothalonil is more effective, as a chemistry (more toxic to Taphrina deformans) but just degrades faster than Ziram. That would I suppose explain why chlorothalonil is rated higher in the east, where an initial kill down of the fungus is good for the whole season. But with longer rainy seasons of some west coast states, more persistence of the chemical might be more helpful.
Perhaps because Chlor. is active against other diseases that are common in the east along with a much shorter window of PLC disease pressure. I should mention that the dominant PLC control used by west coast growers is copper.
I’m getting this info from CHAT GPT and here is the summation.
You indicated earlier that Ziram is the preferred PLC treatment over Chlor in the west… what was that based on
Good question — and it’s worth being precise about what that statement was based on, because it was not a claim about intrinsic fungicidal “strength” or modern trial superiority.
My earlier comment that Ziram tends to be preferred over chlorothalonil for PLC by West Coast growers was based on practice-driven evidence, not headline extension recommendations. Specifically:
When you look at California peach crop profiles and pesticide-use summaries over multiple cycles, a consistent pattern shows up:
Copper is dominant (for cost, resistance, and regulatory reasons)
Among non-copper protectants, Ziram shows up on more acres than chlorothalonil for PLC
Chlorothalonil is present, but less consistently tied to PLC-specific dormant use
That matters because:
Growers vote with acres, not with extension PDFs.
This is not proof that Ziram is “better” in all contexts — it’s evidence that it fits West Coast dormant-spray constraints better.
West Coast PLC pressure (especially coastal / near-coastal regions) is defined by:
Long, drawn-out dormant periods
Intermittent light rains
Fewer chances to respray
High penalty for missing the last effective dormant window
Under those conditions, materials that:
adhere well
wash off slowly
retain surface activity longer
are favored in practice.
Ziram’s dithiocarbamate chemistry has long been known (by growers, if not always emphasized in print) to leave a more persistent surface residue than chlorothalonil under exactly those conditions. .
What this tells me is that for my purposes I’m best off sticking with copper, which has been fine for controlling PLC but also allowed me to harvest bacterial spot susceptible pluots last year. Bac spot has become an increasing issue on certain J. plums varieties as well- it seems to be associated with warmer weather… which is on hold at the moment as we are having a kind of test winter this time around. But in the past such winters have brought lows at least 10 degrees lower than what we are having this time around… but the cold has certainly been persistant. .
What all this tells me is don’t ever listen to AI. Thanks for the heads up!!
Man AI has the thickest brown lipstick I ever seen. Ha! Even has a brown nose it’s so stuck up there!
You come off like a crank when you fail to provide examples of AI’s incompetence- as though you are simply against science and research derived information. All AI does is bring quick access to available information from all available quarters. The search it did to bring forth the information required for my last comment was massive and took it several minutes surveying thousands of documents.
I’m sorry, but even very experienced individuals in any given subject cannot perform this kind of task and your evaluation seems to be entirely emotional, given your lack of specific rebuttal of the infromation I have been supplying.
I see that as a negative contribution. Mud, not information. CHAT makes mistakes sometimes, but I’ve yet to see any comments you’ve made that pointed any out. Meanwhile my CHAT based comments seem to be receiving increasingly positive response from other members. Maybe because they are participating on this forum to learn more about fruit trees any way they can and don’t start with some ideology that bars some useful info sources.
When this conversation started I had no knowledge of the contrasting nature of the chemistry of Ziram and Chlor, or that Ziram was more popular as a treatment against PLC than Chlor with west coast commercial peach growers, but that ultimately, most get adequate control with copper. CHAT gave me all that within minutes.
Commercial growers are managing thousands of acres of fruit trees and cannot afford to waste money. They use academic guidelines as a starting point, but over the seasons modify their management based on real world conditions that university researchers have much less experience with. How they manage their orchards is difficult to acquire information without the use of AI. These people don’t make catchy videos for the internet.