Sticky White Mold on My Cactus

History

• A recent revival of interest in cochineal dye pigments has occurred because it is a non-carcinogenic dye source. The carmine colored dye was highly prized and long-used by the Aztec and Maya people of Central and North America. It was introduced to Europe by the Spanish in the fifteenth century and held exclusively as their import item. Cochineal insect dye was used to color military uniforms, royal dress, artist's pigments and food. By the middle of the nineteenth century, it was replaced by alizarin crimson, which is an extract of the madder plant.

Symptoms

• The cochineal is indigenous to the lower elevations of the western United States and Mexico. It feeds almost exclusively on the pads of the prickly pear cactus. Like the aphid, the cochineal female presses her tubular proboscis into the plant and draws out its liquids. She creates a white, waxy, moldy-looking coating around her body at the same time to protect her from predators. Eggs are produced and a cochineal colony is established on the cactus pad. A home gardener sees isolated spots of white that grow to cover an entire area of the cactus pad.

Treatment

• Spray an affected cactus thoroughly with soapy water followed by clear water. When cochineals are collected as a dye resource they are brushed gently off the plant and are easily dislodged. Water spray works the same way. The correct dilution is 1 tbsp. mild dish soap to 1 gallon of water. Make sure to spray the undersides and where the pads attach. The cactus should be examined regularly for a repeat infestation and treated again as necessary.

Ongoing Care

• Food, light and water are important ingredients to the on-going care of a prickly-pear cactus. Weak plants are more susceptible to insect infestations such as the cochineal scale. Potted indoor cactus thrives when placed near a bright window. Outdoor cactus needs sun for six to eight hours per day. Prickly pear cactus survives on local rainfall outdoors and once-monthly watering indoors. Feeding cactus one time per year with a 10-10-10 fertilizer provides adequate nutrients for healthy growth.