does freezing hurt fungicides-insecticides

mes111(5b -Purling NY & 7b -Nassau County NY)January 14, 2014

I just realized that my supply of fungicides and insecticides, etc. in are not in my garage at home, so I must have left them in the unheated shed in upstate NY. (Immunox, Captan, Copper, Fung-o-Nil, Triacizide etc).

Will the freeze harm their effectiveness.


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Scott F Smith(6B/7A MD)

Generally the answer is no, but there could be an exception I have not heard of. The pesticides that are the most sensitive are "live" ones like codling moth granulosis and for those the instructions are in fact to freeze them to preserve them for longer. So I would be surprised if freezing hurt any pesticide.


    Bookmark   January 14, 2014 at 12:49PM
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I'd guess they are probably all okay. Anything in solid/granule form is going to be likely more stable at low temps. For liquids redissolving any solids/and mixing it well before use would probably be sufficient but I don't have any particular experience with this in my climate.

My lunch meeting for today got canceled so I have some free time:

Immunox = Myclobutanil with or without Permethrin
myclobutanil: stability in frozen food/soil is at -10 to -15C is >2 years. If you have the granules I'm sure it is fine but if you have the concentrate, the myclobutanil is at about 100x the solubility in water so it must be dissolved in something else (alcohol or some other hydrocarbon) so make sure you let it redissolve. In liquid form it degrades when exposed to light.
Permethrin: stable in acidic and neutral pH, unstable at high pH. stable when exposed to light. stable at temperature extremes. In soil increased stability at low temp.

Captan: low solubility and relatively unstable in water. concentrate must be in some other solvent. In most frozen foods it is stable for at least 6 months at -20C.

copper: copper octanoate, sulfate, ammonium complex, etc. all are very stable

fung-o-nil = Chlorothalonil: stable at neutral and acidic pH, unstable at high pH. unstable in food, but stable if frozen. low solubility in water so it must be in some other solvent

triacizide = cyhalothrin: very low solubility in water. light stable. stable 1 year at -20C.

    Bookmark   January 14, 2014 at 2:32PM
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mes111(5b -Purling NY & 7b -Nassau County NY)

Thanx guys

    Bookmark   January 14, 2014 at 9:18PM
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olpea(zone 6 KS)


According to the label of Rally, which is the commercial counterpart of Immunox (i.e. myclobutanil) it should not be stored below 32.

Since most pesticide labels don't warn against freezing, I would say it's very possible freezing could damage your Immunox.

Some pyrethroids (same class of insecticide as Triazicide) are susc. to damage at lower temps, but I think the main concern is separation of the compound. The one concern I'd have about Triazicide is that when I've seen it, it looks to have a water base, whereas other pyrethroids are emulsifiable concentrates which have an oil base. I would think oil based concentrates would hold up better under freezing (since they don't solidify) but that's just a guess.

I agree with others that most pesticides can take freezing. I suppose the best thing to do is look for separation of material. Heat is generally much more destructive to pesticides.

Good luck with it!

    Bookmark   January 14, 2014 at 10:57PM
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jean001a(Portland OR 7b)

Info from "Section 830.830 Pesticide Storage Area"

"Dry, cool, and constructed so as to protect pesticides from direct sunlight exposure or adverse temperature extremes. The temperature in the pesticide storage area shall be controlled according to the pesticide manufacturer's recommendations or label directions. "


Here is a link that might be useful: safe storage temperatures for pesticides & more

    Bookmark   January 15, 2014 at 1:34AM
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The freezing may not hurt the pesticide but it could break and spill a container if the material is water based. I have noticed some materials get cloudy or settle after freezing and need to be shaken. They seem to work fine after that.

    Bookmark   January 15, 2014 at 6:39AM
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mes111(5b -Purling NY & 7b -Nassau County NY)

Thanx for the replies,

I know I used the word "freeze" in my initial question and in my mind (when I wrote it) I was thinking "turn into solid".

But, if I remember my high school chemistry correctly, when we add salt, alcohol etc. to water we lower the solidifying (freezing) temp.

So... does the low temperature cause the damage or is it the process of becoming a solid?

Sorry for the confusing way I asked the question

    Bookmark   January 15, 2014 at 4:09PM
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Scott F Smith(6B/7A MD)

Its usually the turning to solid that causes the damage, but for most chemicals in sprays even that shouldn't cause appreciable damage. I think Olpea has the right idea that separation or some other issue with the mix is the potential problem, not the active ingredient breaking down.


    Bookmark   January 16, 2014 at 8:27AM
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mes111(5b -Purling NY & 7b -Nassau County NY)


I will need to keep a close watch this spring

    Bookmark   January 16, 2014 at 1:55PM
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I concur with the others. As bberry said, you may have split the containers if it was water based/full. You might want to look them over while they are still frozen and set them in a secondary containment vessel while they thaw to prevent leaking.

As for solidifying, it all depends on what the reagent is. Methanol won't freeze till around -100C, but if it is an an oil it may solidify at a more reasonable temp (like how olive oil is a solid in the fridge). Freeze-thawing may destabilize emulsions, so a good shaking may be needed. Salt will lower the freezing temp but as the temp lowers you will get some crystallization of the solutes and again will need to give it a good mixing. As olpea said, resist the urge to heat these in order to redissolve/thaw them.


    Bookmark   January 17, 2014 at 1:48PM
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mes111(5b -Purling NY & 7b -Nassau County NY)


I had packed them all in one of those Rubbermaid 35 gallon storage containers planning to take it with me after I closed the place for the winter, so any spillage is contained.

I will be going ther next week to have a look see


This post was edited by mes111 on Fri, Jan 17, 14 at 14:02

    Bookmark   January 17, 2014 at 2:00PM
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jagchaser(5A NE, -15-115f may frost)

Some herbicides (prowl) lose any affect if they are stored below freezing. Im not sure about the pesticides you listed. The labels will say for sure.

    Bookmark   January 19, 2014 at 10:15PM
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