Wasps prey on young nymphs, which blacken when they die. When repotting, look out for tunnels in the potting mix. If any exist, replace the mix and add gamma benzene hexachloride to the new soil. Diseases Cacti and succulents suffer mainly from fungal diseases. Fungal spores abound in the atmosphere and attack plants in damp or wet conditions, especially in a shady area with similar daytime and nighttime temperatures.
Some fungi accually grow through the plant skin.
Most problems occur in late spring or autunm when condensation from cold nights fails to evaporate from the plants if the next day is overcast. Damping off in seedlings can be avoided by lightly spraying the potting mix with a copper sulfate solution. Other factors include high soil temperatures, exposed wounds and poor soil-drainage. There are many types of fungi, however only twelve are specifically associated with succulent plants. The treament of these fungi are all similar.