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Neem/Soap/Alcohol spray - how long does it last?

6 years ago

Usually I use up what I make straight away as I'm spraying several plants or can find something outside to dump it on. But this time I only have one little new plant I want to spray a couple of times a few days apart as a preventive. First spray done, but have some left over mix. Does this really not keep even a few days? Trying to be less wasteful & more efficient, rather than stingy. Seems wrong to chuck it unnecessarily. Any thoughts or experiences?

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Comments (3)

tropicofcancer (6b SW-PA)
6 years ago
Alcohol should last as long as it is kept well capped.

Diluted neem looses its effectiveness pretty quickly as far as its active ingredient (azadirachtin) is concerned. However, the oil part of neem should still be effective for a while. You will have really shake it well every time you use it. The oil tries separate from the water when left undisturbed. Oil is organic matter and so it is possible that a diluted version can start decomposing/fermenting. A smell test should let you know if it is OK to use.

Pure insecticidal soap in water should remain effective. I do not know how long but a few months should be fine. I am not sure of household soaps since there are tons of other ingredients in there besides soap. In fact, one should avoid regular household soaps on plants anyway.
robin98
Original Author
6 years ago
Thanks Tropic, that all makes sense. Can understand the neem breaking down pretty quickly, but thought the insecticidal soap might last longer than its label says (use within 8 hours). Probably just want you to go through the bottle faster. I will check if the mix is smellier before I use it again. And add a splash more alcohol because I bet there'll be some evaporation in the cheap little handsprayer.

Do you have a set quarantine routine? I brought in spider mites with my last new plant, which I've just gotten under control. So of course yesterday I saw a nice little rattlesnake plant which I couldn't resist. Didn't think of new bugs until I was back home. Must have had a brain fade when I saw its pretty leaves..
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I'm kind of surprised this subject and discussion is being tolerated in an organic forum. Alcohol is a disinfectant - meaning it kills "germs," like beneficial bacteria and fungi. The organic approach is to grow healthy plants with a healthy supply of bacteria and fungi that are resistant to the sucking insects. Down here in San Antonio we find that foliar spraying every two weeks with liquid seaweed (3 ounces per gallon of water) strengthens the plants to resist most sucking insects including (if not especially) spider mites. I'm experimenting with a milk spray (3 ounces or less per gallon) to see if it works as well for a whole lot less hassle and cost. I know the organic approach works on aphids. My roses suffered 8 years of aphids before I went organic. Since 2001 I have not seen an aphid on them. Your mileage may vary, but that's the no-kiddin truth at my house. All I do is topdress the rose beds with an inch of compost every spring and fertilize with a handful per plant of ordinary corn meal every month. We had been composting during the years of aphid infestation, but when we added the corn meal, the aphids disappeared. Another example of organic approach working is from a local organic experimenter who gave me a tour of his greenhouse. He pulled out three small plants in 4 inch pots. The three plants were all touching pot rims and the plant canopies were intermingled. He slid the tray out and showed me that only one of the three plants had aphids on it. It was pretty well covered while the other two plants were aphid free. The only difference was the soil. All three were growing in Wal-Mart potting mix but the two without aphids had been amended with compost, greensand, and ground basalt sand. I realize that three plants do not make a very serious experiment, but in the entire greenhouse, there was only one plant with aphids. Before that I had assumed that once a greenhouse was penetrated by aphids, the entire place had to be quarantined. Guess not.
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tropicofcancer (6b SW-PA)
6 years ago
Did not know that insecticidal soap must be used within 8 hrs. So I am guessing those Ready-to-Use bottles must have something to keep it useful. But I think you may be also right that they just want you to use it faster.

I usually make mine in those 24 oz sprayer and usually less than 24oz for quick spray jobs. I hardly ever have leftover. I have way too many plants anyway.

These days I rarely buy plants (refer to too many plants problem). But I do hit it with an alcohol spray if I do buy one. Most of my pest problems happen indoors in winter. To slow it down I will spray all my plants late fall when they are still outside. My favourite go-to is horticultural oil for this purpose.

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