Zygocactus Problems

Zygocactus, often called "Christmas cactus," can suffer from problems such as rot caused by overwatering, dropping of buds because of improper temperatures or lighting, and failure to thrive due to infestations such as by mealy bugs or brown scales. It is important for growers to provide consistent, proper care to their Zygocactus in order to remedy the underlying causes of such health issues.

Phytophthora parasitica Dast. is a fungus that causes root and stem rot in Zygocactus. Plants experiencing stem rot exhibit water-soaked areas on stems that turn reddish brown as the disease progresses. In addition, root rot causes Christmas cactus plants to develop black or brown, mushy root systems. Root rot generally is a sign the your Zygocactus was planted in soil that did not allow adequate drainage, or it was overwatered. Remove all dead or rotted portions of stems and roots. Replant the Zygocactus in sterilized potting medium.

Mealy bug nymphs and eggs are covered in a waxy coating, which makes treating an infestation difficult. These pests cause problems by sucking out the sap or nutrients from your Zygocactus. Gardeners may see the 1/8- to 1/4-inch insect crawling on the Christmas cactus or they may just see the damage. Symptoms of a mealy bug infestation include cactus tissue discoloration and yellowing. Mealy bugs secrete a sticky substance called honeydew, which coats the cactus. Treat an infestation by spraying your Zygocactus with a recommended insecticide. Insecticide applications will have to be repeated to catch mealy bugs when they are crawlers and have no waxy coating.

Like mealy bugs, brown scales suck the nutrients from Zygocactus and produce honeydew. These scales may reach a staggering population size if ants are tending them. Ants and brown scales have a relationship with each other similar to the relationship ants have with aphids. Scales produce honeydew, and ants feed on the honeydew. In return, ants protect brown scales from their natural predators. Gardeners may see their Zygocactus discolor, wilt, or turn yellow because of the damage caused by honeydew-secreting organisms tended by ants. You can use a horticultural oil to treat your scale problem on your Zygocactus.

Dropping of unopened flower buds is a common problem of Zygocactus, according to the University of Illinois Cooperative Extension. The Zygocactus may have produced too many flower buds during the season to put energy into blossoming. Other factors may be dry soil, improper temperature, or interruption of the plant's required darkness. Zygocactus bloom when nights are 15 hours long or when they are kept in an area where temperatures are around 50 to 55 degrees Fahrenheit. They will not bloom at the normal room temperature of a home.