Question
I have had a large boston fern for many years. Recently I noticed that the underside of the fronds are sticky, almost like there was honey on them. The floor under the fern is sticky also. I cannot see any pests on the plant, and it doesn't look sick, but I have never noticed this stickiness before. What is causing it and how can I fix it? thank you very much.

Answer
Hi Marianna,

Your fern has a scale infestation. Unfortunately, scale is very hard to treat on Boston ferns because the fronds are so sensitive to handling and to various sprays, even non-toxic ones.

On option would be to cut off all of the fronds at the soil line and discard them along with the scale. You could then spray the remaining stubs and soil surface with an alcohol/water/soap solution described below. As long as your plant is otherwise healthy, new fronds should start growing in very soon and you will have a decent looking plant again by the end of the summer.

Another option is to spray only the undersides of the fronds with soap and water (no alcohol). This will hold the scale in abeyance and prevent additional stickiness. However, it will not completely eradicate the scale, so you will have to spray again every month to hold the line.

The last option is to attempt to spray your fern thoroughly. But you should expect consider frond yellowing as a result and I cannot guarantee that the scale will not come back again in several months.

Okay, here is what you need to know about scale and treating it. Scale can be hard to detect. When they are young these sucking insects are slightly oval, slightly raised, translucent bumps about an eighth of an inch long. They can be found along stems and on the undersides of leaves. They don't look like bugs and don't appear to move. As they get older, they develop a hard, dark brown shell and look like a small mole. As the infestation increases, these sucking insects will secrete a sticky substance called honeydew that falls onto leaves, furniture and floors. This stickiness is the most obvious sign of scale and the one that most people notice first.

The key to eliminating scale is to treat even the ones that you cannot see. That means thoroughly drenching all leaf and stem surfaces until they are dripping wet. It is also best if you repeat this treatment all over again in 5 to 7 days to catch any crawlers (the translucent young ones) that you missed the first time. After that, you should check your plant weekly to see if they return.

You may want to try treating scale by spraying the entire plant with rubbing alcohol. This will help break through the hard outer barrier of the scale and kill it. Mix 1 part rubbing alcohol with 8 parts of water. Add a little liquid soap to help it spread.

Important: This spray should not be applied to plants in direct sun or in high temps.

Please let me know if any of this is unclear or if you have any additional questions. If you would like to e-mail me some photos, I may be able to provide some additional insights.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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