Rot on scopulicola hybrid

Trouble shoot problems you are having with your cactus.
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duckworth
Posts: 14
Joined: Sat May 20, 2017 12:41 am

Rot on scopulicola hybrid

Post by duckworth »

Hello :) below are some photos of a T. scopulicola (hybrid?) which now has some black rot where the flesh was exposed to rain. This rot becomes hard in the sun, but after a rain it becomes soft. Not mushy soft - just soft enough that you can make an impression with a fingernail.

This cactus now has a rain cover - but maybe it's too late :( what are your thoughts?

However, the last photo shows that this champion has been through worse in the past - and survived.

Background info - this cactus has been ignored for over a decade. After seeing new growth, we tried to save it. So don't want that to be in vain! Thanks everyone.
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Steve Johnson
Posts: 4514
Joined: Thu Nov 03, 2011 4:44 am
Location: Los Angeles, CA (Zone 10b)

Re: Rot on scopulicola hybrid

Post by Steve Johnson »

Not sure if it's rot or a fungal infection. I've seen both, and my guess is that you're dealing with necrosis caused by fungus. The fact that the affected areas callus over tends to bolster this argument. If I'm correct, keep the plant protected from rain 24/7/365, and water around only the base of the plant. Last thing you'll want is to see the necrotic tissue spread, so don't spray the plant as this may be counterproductive.

Looking at your last photo, your Trichocereus doesn't appear to be healthy. The yellowish-green skin color is a sure sign of chlorosis, due to insufficient fertilizing and/or lack of a robust root system, which will in turn inhibit proper water and nutrient uptake. If your cactus mix is soil-heavy, lean it out more with enough pumice or granite gravel to have the mix draining freely. If you're already doing that, there are two other factors to consider:

1. Fertilizer -- I highly recommend Dyna Gro All-Pro 7-7-7. IMO this is the best fert for cacti and succulents, and I've been using it successfully since 2012 (it's the only fert I'll use). However, we can only get it by the gallon, so it may be more expensive than what you're willing to pay for. Dyna Gro also makes a 7-9-5 in smaller quantities through eBay. Although the NPK balance isn't exactly ideal, it'll be good enough -- plus you'll get the same excellent nutrient profile of minor and micronutrients as the 7-7-7. Dilute 1/2 teaspoon of the liquid concentrate per gallon of water, and fertilize with every 2 or 3 waterings.

2. Watering with rainwater is best, although whether you can or not depends on being able to store a sufficient supply of it. Here in SoCal that's pretty much impossible, since our year-to-year rainfall is too unreliable. If you're in the same boat, you'll be dealing with tap water which is most likely hard. Something else I've been doing since 2012 is acidifying my tap water with 5% white vinegar. I don't know what the pH of your tap water is, but 2 teaspoons of vinegar per gallon should be safe.

Hope this helps!
If you just want photos without all the blather, please visit my Flickr gallery.
My location: Los Angeles, CA (Zone 10b)
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