Hollyhock Rust Seeds
August 29, 2023 1:23 PM   Subscribe

I have seeds from hollyhocks that were infected with hollyhock rust. From my understanding, the seeds will carry the fungal infection. I want these seeds to succeed for Sentimental Reasons. My question: is there a way to treat the seeds for hollyhock rust BEFORE PLANTING? I'm in zone 5a if it matters.

I have planted a round of the Sentimental Seeds at my rental place, and sure enough, they GOT THE RUST. I'm soon moving, and want to find a way to use the seeds at my new place without dooming my plants to a fungal death.
posted by Grandysaur to Home & Garden (4 answers total)
 
No, you cannot treat the seeds before planting. You can only be liberal with strong fungicides, or grow the hollyhocks as annuals (in which case they may not have time to establish rust).
posted by oneirodynia at 1:59 PM on August 29, 2023


More good rust control tips here.
posted by oneirodynia at 2:01 PM on August 29, 2023


Fungicide application prior to planting is an extremely common practice.
"Pre-sowing seed treatment with systemic fungicides is a firmly entrenched practice for most agricultural crops worldwide. The treatment is intended to protect the crop against seed- and soil-borne diseases. "
See here for a recent review, and reference therein.
The thrust of that research is to evaluate negative impacts when deployed at large scale, you won't really need to worry about that for a tiny home application.

This page from Iowa State Extension service has more practical information on which fungicides are better at what.

The biggest problem I see is how you get a hold of a handful of one of these agents for a reasonable price, but I certainly think it's worth a try to help keep a personally valuable strain going. If you have an old-fashioned local seed & supply store around, I'd call them first. Good luck!
posted by SaltySalticid at 6:33 AM on August 30, 2023


That paper linked suggests that fungicidal treatment of seeds should be considered more carefully:

We reviewed the trade-off of pre-sowing seed treatment in defending seeds against seed- and soil-borne pathogens on the one hand and the possibility of losing seed benefiting endophytes on the other. Considering the potentially important role of seed-borne endophytes in seed germination and seedling growth, and being a source of endophyte inoculum for the different tissues of the developing plant, the century-old practice of routine seed treatment should be revisited. The gain accrued by seed treatment in disease management versus the potential loss in crop performance due to disturbance of seed endobiome by seed treatment should be studied for more crops using fungicides exhibiting different modes of action.


In this case Hollyhock rust is not a seed or soil borne pathogen, though the seed can be contaminated superficially if plant parts were collected with them. Because it's not a food crop* and is presumably being sown in a garden with mycorrhizal associations, adding strong fungicides to the soil biome might not serve any purpose other than to disrupt those associations. The seed could be sterilized by removing any plant parts and using household bleach to sterilize:

The two most effective seed disinfectant solutions were chlorine based: dilute household bleach (NaOCl; 0.6% sodium hypochlorite) and freshly prepared hypochlorous acid (HClO; 800 ppm chlorine). Both consistently reduced fungal growth on germinating seeds (by up to a 5-log unit reduction in bacteria) without having a significant effect on seed germination

If your bleach is 5.25% sodium hypochlorite a 1:9 solution with give you 0.6 dilution. You'd then soak clean seed in that for 15 minutes to kill fungal spores and bacteria.


*soils in which food crops are grown on an industrial scale are generally "dead", without any living soil biome.
posted by oneirodynia at 11:57 AM on September 1, 2023


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