Orange spots?

[keithp2012]

I need help with one of my Gymno. I rescued this last year, it was completely flat and brown. Since then it's gotten fatter and better coloring, but it's had these orange spots on the edges and they've gotten worse. I have no idea what they are or how to treat them?

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[Tom in Tucson]

My guess: fungal rust. To reduce the infection, I would remove it from the pot, remove all the existing soil, then put it aside in the shade for the roots to heal. In the mean time, you should acquire some high quality bonsai soil with very little organic matter. After youv'e waited for the roots to heal, plant the cactus in a plastic pot (for this type of cactus), and wait 2 days before watering. Keep this type of cactus shaded and warm until new growth resumes. If the rust persists, spray with any fungicide, and follow the label instructions.

[keithp2012]

My guess: fungal rust. To reduce the infection, I would remove it from the pot, remove all the existing soil, then put it aside in the shade for the roots to heal. In the mean time, you should acquire some high quality bonsai soil with very little organic matter. After youv'e waited for the roots to heal, plant the cactus in a plastic pot (for this type of cactus), and wait 2 days before watering. Keep this type of cactus shaded and warm until new growth resumes. If the rust persists, spray with any fungicide, and follow the label instructions.

How does fungal rust form and why does it affect the roots?

[Tom in Tucson]

My guess: fungal rust. To reduce the infection, I would remove it from the pot, remove all the existing soil, then put it aside in the shade for the roots to heal. In the mean time, you should acquire some high quality bonsai soil with very little organic matter. After youv'e waited for the roots to heal, plant the cactus in a plastic pot (for this type of cactus), and wait 2 days before watering. Keep this type of cactus shaded and warm until new growth resumes. If the rust persists, spray with any fungicide, and follow the label instructions.

How does fungal rust form and why does it affect the roots?

Fungal rust. like most fungi thrive on 3 things: a moist atmosphere, unhealthy tissue, and low light conditions. In your case the rust is an indirect result of the soil. The soil led to poor root growth. This led to unhealthy stem tissue. This became a breeding ground for the fungus.