My Cactus Is Rotting From Within

Causes

• Pests such as bacteria, fungi and insects enter cacti through wounds or eat their way into the plant. Commonly, fungi such as Lasiodiplodia theobromae, Phialocephala virens and Fusarium oxysporum enter through damaged stems. Stem damage may be caused by improper grafting or planting practices. Furthermore, over watering or fertilizing the cactus causes rot. Cacti cannot thrive in poorly draining soil or other moist conditions. Gardeners who use a potting soil that doesn't contain material such as gravel, sand or peat can experience rot in their cacti. Encouraging rapid growth through over fertilizing also promotes rot. Over-fertilized cacti bloat and their skin can tear, creating an opening where harmful pathogens can enter.

Symptoms

• Cacti can experience three different types of rot: root, stem and grafting. Root rot causes mushy, discolored roots. Gardeners can tell their cacti has contracted the disease by lifting the plant out of the container and inspecting the root system. Also, cacti with root rot display stunted growth. Stem rot starts at the lower portion of the plant and works its way up. Symptoms of stem rot include discoloration, black spots and tan discoloration. Grafting rot is often caused by pruning tools that have not been sterilized. The area around the grafting union exhibits discoloration when grafting rot is present.

Treatment

• Regardless of the type of rot a cactus has contracted, gardeners use the same basic treatment method. Sterilize a sharp knive with a solution of 70 percent denatured alcohol and 30 percent water. Cut into the healthy part of the cactus to remove the diseased rot area. Apply either sulfur powder or rooting hormone to the cut area to treat the disease. Repot the plant in fresh cactus potting mixl. Avoid watering for a couple of days.

Other Factors

• Removing rot from the cactus is not the end of the treatment. Gardeners may remove the rot, but the disease can occur again if certain cultural practices aren't amended. Water your cactus only when the soil is completely dry. Apply enough water for it to drain from the draining holes. Allow the surface of the soil to dry out in between waterings. Cactus plants go dormant in the winter; therefore, they need less water. Also, keep the container on a saucer filled with pea gravel to help with drainage. Do not leave in a saucer with standing water.