Aloe vera is only one of 400 species of the Aloe genus. Its leaves grow in rosettes and are fleshy. The leaves are thick, succulent and have spines. The flowers grow on a single stem and are orange or red. Aloes originated on or around the African continent. It grows in many different climate--even in the mountains. It prefers rocky soil but will grow in rich soil.
Colletotrichum is a fungus that causes anthracnose. It thrives in moist conditions, or if the aloe is grown in the shade and is irrigated from the top instead of the bottom. The infection causes lesions on the leaves. It produces a red or orange spore mass that grows in the lesions. The spores spread via raindrops or by overhead watering. Remove and discard leaves with lesions, and avoid watering from above to control the disease.
Echinocereus is caused by Helminthosporium, which is a spore-producing pathogen. The spores are spread via wind-driven rain and from watering above. If the aloe has dark, shrunken areas that are water-soaked, remove the leaves with those spots. It can start anywhere on the plant and causes soft rot inside the plant. Fungicides that contain thiophanate-methyl help prevent infection, according to the Arizona Cooperative Extension, but water management prevents the disease.
Root rot is caused by several different soil-borne pathogens and Fusarium. If you notice the disease, according to the Arizona Cooperative Extension, you will most likely find the agave weevil. The weevil introduces soil-borne pathogens and Fusarium when they feed on the aloe. Once the microbes enter the plant, there is no cure. Remove and discard infected plants, including the rootball. Practice good watering and fertilizing techniques to keep the plants healthy. If you notice agave weevils, treat them with pesticides. Check the aloe for signs of root rot, including dark, shrunken areas and water-soaked areas. Sanitize the soil around the infected plants, so that the pathogens are not spread to other plants or to future plantings.