Issue: January 15, 2005

Umbrella plant with sticky substance on its leaves

I have an umbrella plant with what I think is an infectious disease. The leaves are coated with a very sticky substance, and this "sap" drops on the floor and makes the floor sticky. The plant is losing its leaves after they turn yellow.

I had this problem earlier in the year with an ivy plant, but I thought my daughter had spilled soda pop on it because it was sticky. This plant eventually dried up and died.

Is this some form of fungus? I can't see any fungal growth or insects.

I hope to save the plant because it is at least 30 years old and was a 'pet' belonging to my late mother.

Can you offer any suggestions?

It is probable that there is an insect causing what you have described. The sign of their presence is the sticky substance called honeydew. Honeydew is a sugary, syrupy substance excreted by the insects after consuming sap from the plant.

There are several insects that excrete honeydew. The most common of these are aphids, mealy bugs, and scale insects. Of these three, the scale insect is most difficult to see because it covers itself with a (usually) brown waxy covering so it looks like a bump on a stem or a small brown bump on the bottom of a leaf. It betrays its presence by the honeydew that collects on surfaces below the place where it is feeding on the plant.

Scale can be difficult to eradicate. If the infestation is too great, it is often best to dispose of the plant to protect nearby plants. However, as you described, your umbrella plant has sentimental value to you and is worth saving.

Isolate it from other plants to reduce the chances that the scale insect will infest other plants. When caring for the plants, go to the umbrella plant last so the insect will not spread on your hands, clothing, or houseplant implements. You can treat with chemical insecticides (organic/low toxicity or commercial insecticides). Try using the least toxic means of treatment at first, especially since you will be treating the plant indoors during the winter. You can use horticultural oil or insecticidal soap applied to the under surface of leaves and stems where the scale insects (brown bumps) are located. Apply the oil with a cotton ball or cotton swab. With gentle rubbing, the scale insect may be removed along with any eggs or scale offspring under or nearby the larger parent scale. Some people use rubbing alcohol, but this only allow physical removal. Horticultural oil and insecticidal soap have insecticidal properties and will kill some of the insects that remain. Horticultural oil and insecticidal soap are labeled for control of insects and provide directions on their label for treating houseplant insects.

There are also systemic insecticides that may be applied to the plants, but these should be applied when the weather is warmer and the umbrella plant can be taken outside without fear of cold damage. The systemic insecticides have the advantage because the chemicals will enter the phloem of the plant that carries the sap on which these insects feed.

Whenever using chemicals (including the insecticidal soap and horticultural oil) read and follow the label directions. If you do not understand the directions, contact your local Cooperative Extension Service agent for assistance.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!