What do you use on Rhizosphaera?


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Has anybody played around with options enough to feel that you can say one product is definitively better than others?

Spruce trees are just coming out up here, so I've done round 1. I have been using Chlorothalonil, but that label switched from signal word "Caution" to "Warning". I try to avoid that if possible...both for applicator health, but also I prefer to explain to clients who ask about how toxic something I am using the 3 signal words found on products and that the one I am using is the lowest of those 3... Can't do that with Chlorothalonil any longer. I also like to switch fungicides to avoid building a resistant population.

I do see some recommendations on some Extension factsheets for Thiophanate-methyl. That still has a "caution label" (but when you put the 2 together, you get a "Warning" signal word...).

Open to other suggestions.



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Prune at ankle height and blame landscapers, deaigners, garden centers, and landscape architects.

T-methyl buzz has been a strong tendency towards disease resistance of late. Copper is still effective but your residual can be sketchy with lots of rain. I'm not aware if any Triazoles with the labeling, perhaps a Strobi?
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I've heard, thanks for chiming in!

I was trying to avoid switching from a "Caution" to a "Warning" signal word. I certainly don't want to make the jump to "Danger".

I think I'm going to use Tourney this spring - alternating with either a "Caution" labeled Chlorothalonil or 3336. Tourney is labeled for rhizosphaera, and I've heard it is effective.
You should really avoid using thiophanate-methyl on its own because it has a high chance of building up resistance quickly to most fungi. It is a fairly host-specific fungicide which means it attacks the fungi in a very specific way (I can get you that information if you want), and fungi can easily overcome that mode of action (MOA).

It's always best to mix it with another fungicide. Mixing with chlorothalonil works well for Rhizosphaera. Chlorothalonil has a less specific MOA and therefore has less of risk of building resistance.

Copper fungicides also work well, but if the tree is next to a solid object (fence, house, pavement) you might not want to use it. It will cause staining.

As far as your concerns with the signal words, those are in relation to your direct exposure to the product, like if you weren't wearing any PPE at all. If you're using and wearing the correct PPE then you're protected. Organically formulated (meaning that they contain carbon - no meaning used for organic agriculture) degrade once dry due to the exposure to sunlight, microbes, air, etc. so they're not a "danger" once they're dried.

Here's a good fact sheet on what the signal words mean. I use it for reference all the time and find it helpful. http://npic.orst.edu/factsheets/signalwords.pdf


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Junction and cu pro I think mancozeb too ha e cooper in them and that’s what works really well with rhizo, diploida and dothistroma. All caution
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