Do any fungicides actually work as a preventative for sensitive species

[Aloinopsis]

Do any commercially available fungicides work as a preventative against rotting in cactus?

I know that prevention is always the best approach. It is best to keep plants dry and water them infrequently.

But I also see people talking about using fungicides as a preventative. Does this really work? And if so, which specific types of fungicide?

When I lived in Florida, I lost several Astrophytums and Mammillarias to rot simply because the air was tropical and humid. Does fungicide work in situations like that?

[CactiJim]

I don’t think fungicide will do anything to help your cacti if the problem had to do with the humidity in the air. If the humidity in the air caused fungus to grow on your cacti, then I think a fungicide like neem oil or that copper fungicide at Lowe’s/Home Depot could help.

As for the fungicide working or not, I think it definitely does work and helps. I used neem oil to spray my cacti after I took some pups off, and I saw that in the areas where the offshoots were particularly clumpy and close together, was some fungus and rot occurring. I sprayed some neem oil on the affected area and the cactus is healing nicely. It also helps to prevent fungus/mold from developing on the “open wound,” if you will, from where the pups were. Just be careful not to spray the neem oil during times where the sun will be hitting your cacti, as it can really cause severe burns. I applied the neem oil after the sun had set. You could even clean the neem oil off the next morning before the sun hits your cacti if you wanted to be extra cautious.

If the air is really humid, like in your Floridian climate, then I think you would benefit some decreasing the amount of organic matter in your cactus soil mixture (bark, peat, etc) and using a majority of pumice, lava rock/cinder/fines, turface (calcined clay), expanded shale, river/coarse sand, or other things of the like. You would just have to probably fertilize more often due to the high drainage and porosity of the new mixture.

I’m no expert, though, these are just my two cents. Maybe more seasoned cacti aficionados can give you some better tips or attest to my advice.

Hope this helps bro!

[Aloinopsis]

I could be wrong. But as I understand it, it is not necessarily the humidity in the air that directly causes it, rather it is the humidity in the air which easily allows the spores to travel on the air and get into the soil.

From what I have seen, people treat the whole plants so that the roots and soil are less prone to fungus.

By the way, when I lived in Florida I did used 100 per cent pumice, and some cacti still rotted even with proper care. It was mostly Astrophytums and Mammillarias like Mammillaria saboeae.

However it was a brilliant climate for orchids and ferns.

[CactiJim]

I could be wrong. But as I understand it, it is not necessarily the humidity in the air that directly causes it, rather it is the humidity in the air which easily allows the spores to travel on the air and get into the soil.

From what I have seen, people treat the whole plants so that the roots and soil are less prone to fungus.

By the way, when I lived in Florida I did used 100 per cent pumice, and some cacti still rotted even with proper care. It was mostly Astrophytums and Mammillarias like Mammillaria saboeae.

However it was a brilliant climate for orchids and ferns.

"I could be wrong. But as I understand it, it is not necessarily the humidity in the air that directly causes it, rather it is the humidity in the air which easily allows the spores to travel on the air and get into the soil."

That makes sense, actually. I think you're right.

Wow, even with a 100% pumice, you still experienced mold/fungus? Try it then, man. I think you could spray it once a month or something. I actually sowed some seeds about 12 days ago, and I applied just one spray of neem oil on the surface of the pots before I sowed my seeds, and I have yet to see any mold or fungus develop, so it seems to have helped. About 25 days ago, I sowed seeds and didn't spray or sterilize anything, and I started getting that spidery/fuzzy white mold creeping on the surface of the pots. So I think a general fungicide like neem oil or that copper one at the hardware stores does help.

[keith]

100% pumice will hold more water than a 50-50 mix of pumice and gravel or sharp sand. I figured this out the hard way .

I use hydrogen peroxide as a fungicide its OK the advantage is if it gets on my hands I don't get poisoned.

[CactiJim]

Neem oil is poisonous?

[greenknight]

Neem oil is poisonous?

Neem oil is mildly toxic if ingested, causing nausea and drowsiness. Getting some on your hands wouldn't be a problem, just don't drink it.

[CactiJim]

Neem oil is poisonous?

Neem oil is mildly toxic if ingested, causing nausea and drowsiness. Getting some on your hands wouldn't be a problem, just don't drink it.

Oh wow, I did not know that. I never get it in my skin, and would much less ever drink it. It smells absolutely horrendous. But it does seem to help my cacti with mold/fungi when I see some. Seedlings seem to be unharmed by it, too. I gotta try that Hydrogen peroxide, though.

Thanks for the info, Greenknight!

[DaveW]

I would have thought neem oil was more an insecticide? They use neem oil in shampoos for killing nits on children's heads, so not a problem on the skin. Many things are toxic if drunk.

https://www.discoverneem.com/home-remed ... -lice.html

There are narrow and broad spectrum fungicides. The narrow ones will only treat certain moulds, whereas the broad spectrum ones will kill most so look on the container to see if appropriate. Also if a contact or systemic one.

"Breadth of activity: narrow-spectrum or broad-spectrum. Narrow-spectrum fungicides are effective against only a few usually closely related pathogens. These usually have single-site activity and are often systemic. Broad-spectrum fungicides can often control a wide range of unrelated pathogens. These usually are contacts with multi-site activity, but some have single-site activity. Several fungicides have activity that places them on a continuum between narrow- and broad-spectrum fungicides."

https://www.apsnet.org/edcenter/disimpa ... 0pathogens.

[keith]

Don't know about neem oil I was writing of fungicides and pesticides in general . After a bad malathion experience years ago I am pretty careful now. I wear gloves and a mask now when I spray. Before I just wore gloves and got some kind of sinus headache that lasted too long. H2O2 I don't have to bother with any of that . I don't know how well it works compared to neem oil never used need oil but it sounds messy IDK ?

"the acute toxicity of fungicides to humans is generally considered to be low, but fungicides can be irritating to the skin and eyes. ... Chronic exposures to lower concentrations of fungicides can cause adverse health effects. Most cases of human fungicide poisonings have been from consumption of seed grain.Sep 13, 2017

[Aloinopsis]

100% pumice will hold more water than a 50-50 mix of pumice and gravel or sharp sand.

This is true. I have trouble locating gravel or sharp sand that is approximately the same size as the pumice I use.

[DaveW]

The EU is probably far quicker in banning any chemicals they consider human or environmentally unfriendly Keith than the USA is. Particularly banning them for use by amateurs who they think will not take the same precautions in their use as professionals.

You do have to be careful. I remember a Dutch cactus grower a decade or so ago obtained some Temik, supposedly only to be used by professionals usually in "space suits" in order to kill nematodes in his cactus bed. Unfortunately he was soon very ill since it affected his nerve endings and he never really recovered and died a few years later.

https://en.wikipedia.org/wiki/Aldicarb

Due to an alarming fall in bee and pollinator numbers the EU has banned some fungicides. Many people do not realise just how much we depend on bees and other pollinators to pollinate our crops to produce our food. Obviously a farmer cannot go around even an acre field with a pollinating brush to set fruit as we can with a few cacti in our collections.

https://geneticliteracyproject.org/2019 ... umblebees/

[keith]

California will ban things way quicker than say Arizona or Texas , not sure how it compares to the EU ?

Dutch cactus grower a decade or so ago obtained some Temik," yea that's just very scary. I work with the wives of AG workers they have to get their blood tested as they spray crops with IDK what ? We grow many crops year round here in Oxnard .

Malathion is an insecticide in the chemical family known as organophosphates. The Malathion I bought was made by chevron and I think because the actual Malathion concentrate is regulated to be very low the chemical company adds volatile chemicals to boost the effectiveness of the product. Who knows what effect they have then ??

This why I add diatomaceous earth powder to my soil mix I hate using pesticides. Hard to find and when you do find them they don't work as well as what professional growers can get so any imported bug is pretty resistant . I bought a concentrated jar of Merit back in the late 1990's for about 80 bucks still have it and kelthane for spider mite , still have it both still work , I hope they are pretty old but you cant get them anymore.

Merit its way better than the old organophosphates I used to use , Isotox, Cygon, not very effective and smelled terrible. This is also why I don't buy cactus from nurseries any more only online professionals who wont ship me bugs. Back in the 1990s when I started growing cactus again boy did I have bug problems. Almost gave up the hobby. Merit + diatomaceous earth + growing from seeds saved it. Although before merit I did have some luck with Nicotine water + soap + alcohol. I told Steve Brack at Mesa about this he said " you made nicotine sulfate that's toxic to all life forms" . I was thinking yea so what cant be as bad as that Malathion which I gave away to a co-worker who use it on his roses he was happy all the aphids died.

Sorry for the long post this goes way back to the mid-1990's. But Fungicides ? Don't know much about them ? I use hydrogen peroxide and root tone as fungicides.

[keith]

Aldicarb is a fast-acting cholinesterase inhibitor, causing rapid accumulation of acetylcholine at the synaptic cleft. It is widely used to study cholinergic neurotransmission in simple systems such as the nematode C. elegans.

Exposure to high amounts of aldicarb can cause weakness, blurred vision, headache, nausea, tearing, sweating, and tremors in humans. High doses can be fatal to humans because it can paralyze the respiratory system.[6]

In South Africa (where Aldicarb is popularly known as Two Step) it is widely used by burglars to poison dogs

[CactiJim]

Wow Keith. You seem to know a lot about this stuff!

Sow what is the general consensus when spraying seedlings or the soil media? Will simple Hydrogen peroxide suffice, or will some of that copper dust fungicide help as well?

I don’t really like the idea of sterilizing the organic material in a seedling mix because you also kill beneficial bacteria and the like (I don’t mind when it comes to sterilizing mineral components like coarse sand, pumice, and lava fines/cinder etc).

But is there a way to not sterilize organic material (that also has beneficial microbes) AND plant seedlings while also preventing/lessening the chance for mold or fungus to develop?