Hey, Thanks for quick respond. I live in Barbados so we have humid conditions but lots of sun at the same time. I grow them outside but I do control watering. It spreads to other cacti and do not know how to stop it. I did some research and neem oil may help. Who or what else can help???

I've never tried it, but I've heard that spraying plant with a spray for athlete's foot (caused by a fungus) can help....

Sounds interesting, one will have to be a tester for good of all. Im trying to change the soil for more mineral and will use some fungicide .

As per my research it looks like rust fungus, nasty thing!

Thanks for help !!!

Yes, if not controlled it will spread to the rest of your collection. They spread usually by water droplets/rain/wind/contact. Don't let that happen!

Sulphur is a popular fungicide, there are many other commercial ones that may help you treat the affected plants.

I am not sure neem oil helps or not - if you treat with neem, ensure your cacti are not in full sun afterwards or they will burn.

Thanks everyone !!!!

The neem idea is okay as a prevention measure and might help it from spreading though out the single cacti but as your cacti already has a fungus I would lean toward a different manner for treating .

There are some cacti that do preference higher humidity from time to time but yours is a arid cacti If it's humid every day outside you may want to consider a green house for better climatic control for your arid cacti.

How would you treat in this case?

Not really easy to see but looks like your cacti are planted in sand. The dark stuff on top of the sand might be algae. Use a potting mix that will dry out better. However, I don't know what you can get in Barbados. Generally, your cacti look good. The first looks like a barrel cactus. The second looks like a Gymnocalycium.

You got that right my friend, first one is from seed,2 year old, Ferocactus i think, second is a cutting I stolen from nursery :) just broke small piece, no big crime :) I think is a Gymnocalycium as well.

I have changed soil already for a bit more mineral, I usually mix sand with soil 50/50, it should be 70/30, I do 50/50 only because it is Barbados and everything is dry next day and more organic soil = more food, but last rain season in the Caribbean was quite long and I think that some algae build in few cases, so nicely spotted Polypompholyx.

I do not know how to use fungicide on Cacti, anyone ??? How often, how to apply???

Shall I remove affected places and use cinnamon to heal cacti or just use fungicide first and wait what happen???

Thanks everyone for helping !!!

Cheers

Marcin

Spray them at dusk so they spend the next 8 or so hours out of the sun. If you are using a water-based spray, you can just leave them where they are. IF your spray has oils in it, you may have to rinse them before the sun hits them---this is just a guess on my part since I don't have cacti and I don't know how sensitive they are.

I have treated leafy outdoor plants and for mildew at least, two treatments were enough, one week apart.

When you say remove, do you mean cut it out? I wouldn't, since that will only expose more plant tissue and leave a bigger scar. Spray on the spot.

Long-term, I'm going to suggest doing a walk-around in your yard. Find the most windy spot that still gets full sun. Then relocate your affected pots there. This thing can spread. In your climate, outdoors may not be enough--you need air movement which can often be helped by careful pot placement so wind or breeze is not blocked by wall, fence, other plants or whatnot.

Sample instructions for one combination pesticide/fungicide used in the USA, Bayer 3-in-1. Active fungicide ingredient is Tebuconazole.

1. BEFORE YOU USE: Lots of important safety precautions on the label, such as what to wear, do it outside, etc.
2. Shake well before use, before and after mixing.
3. Adjust spray pattern, spray 12 inches away.
4. For diseases repeat every 7-14 days as necessary.
5. Do not apply when bees are foraging.
6. Do not apply to flowers or when plant is blooming.
7. Do not wet the foliage one hour after application.
8. Keep children and pests away, do not re-enter area until dry.
9. Do not let run off into storm drains, surface waters, etc.

Depending what you buy, there will be different recommended application instructions as you need to deliver the fungicide in the most effective manner possible.

At the moment I was able to get fungicide called Champion ( turquoise powder ), I have followed instructions regarding dosage and I did spray few affected plants. Will repeat it in a week time. I was not cutting out affected parts as it was suggested to me.

Now I can see that the place where I kept my cacti is a bit blocked from wind. Fortunately I spotted those orange spots early and I have only few plants affected.

I will definitely relocate affected plants and will make sure that there will be more air flow...

Thank you all for help, really appreciated !!!

Marcin

Good luck!! Not sure how much is said on the label, but I saw these very detailed label instructions. Says 1 tbsp / gallon dilution rate, repeated every 7-14 days as needed for ornamental plants. It may leave some residue as it is a copper solution (not sure if permanent, but probably not?).