Red Colors in Lower Part of Cactus House Plant

Rot

• Because cacti have water-filled tissues that they use during drought, they are highly susceptible to contracting a bacterial or fungal disease below their surface, according to Cacti Care. Bacterial and fungi thrive in moist organic tissue. Cacti rarely develop rot when growing in the wild. High temperatures and sunlight dry out the cacti tissues. However, gardeners who overwater their plants or keep them in containers that lack draining holes cause rot to develop on their cactus houseplants.

Symptoms

• Typically, rot starts on the lower part of the cactus plant and moves up, according to Kada's Garden. Gardeners may see red, brown or black discoloration on the stem of their plant. The discoloration witnessed on the surface of the cactus tissue is not as harmful as what is happening below the tissue. Also, gardeners may notice that the discoloration or rotting stemming from a wound made in the skin. Wounds made in the cactus create the perfect entryway for harmful pathogens.

Treatment

• Treating your cactus' rot problems involves surgery, according to Kada's Garden. Sterilize a sharp knife with a mixture of 70 percent denatured alcohol and 30 percent water. Cut into the healthy portion of the cactus, because at least one to two inches beyond the discoloration harbors the fungus. Dust the cut area with sulfur powder or a fungicide chemically formulated to treat cactus rot. Keep an eye on the area to make sure that the fungicide kills the rot.

Proper Watering

• Proper watering prevents rot from infecting your cactus houseplant. Avoid watering your cactus after it has gone dormant for the winter. Furthermore, refrain from watering when the surface of the top soil is wet. Allow the surface of the soil to dry out in between watering. Water your cactus plant until it starts draining from the holes on the bottom of the container. It is also important to use rain or bottled water to prevent salt accumulation in the soil.