Question about my cold hardy cactus. - Ask Extension
Hello, I have several cactus that are cold hardy and survive the winters here. Last year they started getting brown patches on some of the paddles. ...
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Question about my cold hardy cactus. #870514
Asked May 28, 2024, 8:11 PM EDT
Hello, I have several cactus that are cold hardy and survive the winters here. Last year they started getting brown patches on some of the paddles. I tried scratching it off and it does not appear to be bugs, but spraying with a copper antifungal spray didn’t help either. These are 2 paddles I removed from smaller cacti where only one section had the spots.
Anoka County Minnesota
Expert Response
Is the damage only on one side of the pads? If so it could be mechanical damage from hail or other mechanical things. Or Corky scab is another possibility. This is thought to be a combination of factors. See the website below for details.
If it is on both sides it might be insect damage. You wouldn’t necessarily see the insects, only the damage. There are other diseases but this is not enough information to diagnose those. A sample could be sent to the Plant Disease Clinic if these are high value plants to you. https://pdc.umn.edu/
The following websites may be of some help.
1. https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/cactus-scab-treatment.htm
2. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1399.pdf
If it is on both sides it might be insect damage. You wouldn’t necessarily see the insects, only the damage. There are other diseases but this is not enough information to diagnose those. A sample could be sent to the Plant Disease Clinic if these are high value plants to you. https://pdc.umn.edu/
The following websites may be of some help.
1. https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/cactus-scab-treatment.htm
2. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1399.pdf
