Sunscald and fungal problems can occur on cacti and succulents.
This disorder could also be referred to as sunburn or sunscald. The plant becomes bleached, pale, and discolored. This usually happens over a fairly short period of time. In addition, irregularly shaped, reddish-brown spots can develop as a result of the sunscald.
The solution to this problem is obvious. Provide the plant with some protection from direct sun, particularly from exposures where they receive a lot of afternoon sun.
If youíre taking your cacti or succulents outdoors for the spring and summer months, do this with care. If you plan to put them in sunny locations, harden them off gradually so they have time to adapt to full sun. Hardening off is done over a period of a week to ten days or so by gradually increasing the amount of time that the plant is given full sun. This allows it to acclimate properly without damage.
Fungal Problems and Mold
Typically, this manifests itself as damping off of seedlings and white mold.
There are ways to minimize such problems. First, provide the plants with good air circulation. Next, be sure they are receiving enough sunlight for that particular species of cacti or succulent. Finally, donít allow the soil to stay chronically moist. Obviously, certain species, such as the Christmas cacti and the other jungle species, need a slightly more moist soil than other kinds of cacti and succulents.
Proper sanitation also goes a long way in preventing fungal diseases in the first place. That is one of the reasons I always disinfect pots and trays before I reuse them. I soak them in a bleach solution and rinse them well. This destroys any fungal spores on the containers. Also, always use a fresh, sterile potting mix, especially if youíre dealing with seeds.
It also helps if you clean the area where you display your plants. Clean all light garden shelves, windowsills, and the like with soap and water, or bleach.