Cactus Diseases

Sunburn

• Sunburn affects cacti that are not acclimated to direct sun. The most common symptom of sunburn in cacti is the yellow color of the epidermis. Some cacti species, such as barrel and columnar cacti, are especially prone to this disease. Placing the plant in the same direction as it had been growing is one way to reduce sunburn. Sunburn also can be avoided by purchasing plants that are acclimated to sunlight. Sunburn is intensified by lack of water, so watering the plants appropriately can minimize the effects.

Desiccation

• Cacti need water just like any other plant. While overwatering can have adverse effects on a cactus, the lack of it may eventually kill it. Lack of water may cause desiccation, and high temperatures can speed up the process. Desiccated cacti lose many of their roots, so it is better to water them gradually, increasing the amount progressively over several weeks. Abundant watering on a cactus with damaged roots can cause the plant to rot from sitting in moist soil.

Rot

• Rot affects the roots, stem or the crown of cacti, and it is caused by fungi and bacteria. The fleshy tissue of the cacti is a type of environment where bacteria thrive. Cacti tend to rot in moist soils with high organic content and when they are overwatered. The rotting process usually begins from the bottom, with the roots being affected first. This makes the process difficult to spot, as from the top the cactus looks fine. Often, once rot is detected, the plant is already dead. When rot is spotted in time, you can save the cactus by removing the entire affected part.

Cactus Longhorn Beetle

• The Cactus longhorn beetle is a shiny black bug that attacks several species of cacti, including the barrel cactus, prickly pear and cholla cactus and young saguaro cactus. The adult beetle feeds on the terminal buds of the cacti, while larvae may burrow into the roots and cause death of the plants. The beetles are more active in the early morning and late evening, and they are easier to detect and destroy during these periods.