On-line Guide to the positive identification of Members of the Cactus Family
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How does fungal rust form and why does it affect the roots?Tom in Tucson wrote: ↑Tue Sep 19, 2023 8:20 pm 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.
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.keithp2012 wrote: ↑Tue Sep 19, 2023 8:59 pmHow does fungal rust form and why does it affect the roots?Tom in Tucson wrote: ↑Tue Sep 19, 2023 8:20 pm 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.