Question
I have a mature Ficus tree that is doing well in our Brooklyn apartment in front of an East window.  The first week I brough it home from the store I noticed one or two black dots on the leaves underneath.  The dots did not move and I did not worry about them but then they multiplied. I would cut the leaves with dots on them off with a scissors but somehow they just keep reappearing.  If I don't do anything they gradually multiply and there are more and more of them.  Should I worry about this?  I don't think these are bugs - I have checked pretty carefully and they do not move.  I don't know where they came from.  I really don't like the way they look.  Do you know what they are?

Answer
Hi Erica,

If the black dots are sightly raised bumps that scratch off easily with a fingernail, then they are probably scale insects.

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.

I do not recommend any pesticides because they are all hazardous to use and not 100% effective against scale. The best non-toxic treatment for mealybug and scale is called Brand X Foliage Cleaner. It is available through Southwest Plantscape Products in California (www.southwestplantscape.com). Their phone is 1-800-333-7977.It is a silicon-based product so it is very slippery. Its ability to penetrate is probably the key to its effectiveness because it gets into the tiny crevices that other sprays miss. However, Brand X does sometimes cause Ficus trees to defoliate temporarily.

You may want to try spraying with rubbing alcohol that will help break through the hard outer barrier of the scale and kill it. Mix 1 part alcohol with 5 parts of water. Add a little liquid soap to help it spread.

Sun Spray Ultra Fine horticultural oil is also mixed with water and effectively smothers the scale. Complete coverage is important.

Another good non-toxic spray is Hot Pepper Wax. Its main ingredient is hot cayenne pepper that overheats the plant pests. There is an information website for it at www.hotpepperwax.com.

Finally neem oil works similarly to horticultural oil. It should be diluted with water and Pine Sol to counteract the onion-like odor. All of these are available nationwide at plant and garden centers and also by mail order.

Important: None of these should 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.

If this information has been helpful, please click the Rate Volunteer bar below and enter a rating and nomination for me. I am a volunteer on this site so Ratings are the only compensation I receive for answering plant questions.

Visit my website at  www.HorticulturalHelp.com
  
Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]