Please HELP! White/brown spots on Opuntia microdasys.

Trouble shoot problems you are having with your cactus.
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cactusmactus
Posts: 4
Joined: Thu May 14, 2015 5:06 pm

Please HELP! White/brown spots on Opuntia microdasys.

Post by cactusmactus »

Hey, everybody. Last year, shortly after my opuntia microdasys grew two new pads, the new pads developed white spots which eventually grew and turned into the rust color you see in the picture. I'm honestly not sure if it's spreading or if the original spots are just becoming more evident as time goes on. If it is spreading, it's very slow. Does anybody know what this is? Again, it's not affecting the original pads, just the two new ones. Should I just remove them? Any advice would be greatly appreciated. Thanks!

PS I have lots of other cacti which are all very healthy so I don't believe that this is a problem with light or over watering.
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hegar
Posts: 4596
Joined: Mon Jan 23, 2006 4:04 am
Location: El Paso, Texas

Re: Please HELP! White/brown spots on Opuntia microdasys.

Post by hegar »

Well, it is difficult to speculate about the reason for these lesions. They may well be caused by a fungal pathogen. Examine the largest spots for tiny dark grey specks or perhaps a ruptured epidermis (outer skin) showing little bumps with a yellow or pink pigmentation. Also, you may see fine whitish growth covering the lesions. If you do have a good hand lens, you will be able to spot many of the problems that affect your plants.
If you do see in increase in the number of the lesions or you see them grow, you most likely do have an infective agent (disease).

To be on the safe side, it may be best to cut that cladode (pad) off at the joint and discard it. That way you remove a possible source of fungal inoculum (spores) and the other parts of your plant will stay healthy.
Opuntia microdasys is a quick growing, vigorous cactus and will replenish the lost pad rather quickly.
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greenknight
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Joined: Tue Apr 30, 2013 4:18 am
Location: SW Washington State zone 8b

Re: Please HELP! White/brown spots on Opuntia microdasys.

Post by greenknight »

Agreed. They look bad, anyway, removing them will only improve the plant.
Spence :mrgreen:
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