Question
QUESTION: I have about 6 topiary plants and 2 palms (I forgot the type of palm) . They have all developed black raised spots and yellow leaves. The topiary plants have lost the leaves in various sections.  

I water them all twice a week and they get plenty of sun. It looks like a bug or mite. It started on the palms and then moved over to the topiary plants. I bought a spray but not sure if I am using a correct treatment.

Can you please advise me of a treatment.


ANSWER: Hi Melanie,

Topiary refers only to the style of the plant, not to the plant species. However, most topiaries use Hedera ivies so I will assume that is what you have. It is also important that you know what kind of palm you have as different species have very different requirements. If you email photos to my address below, I can ID them for you.

If the pests are hard brown bumps that scratch off with your fingernail and you are finding stickiness on your plants, the you have  a scale insect infestation. Please let me know if this is not applicable.

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 5 parts of water. Add a little liquid soap to help it spread.

For more resistant infestations, 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 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.

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.
     
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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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




---------- FOLLOW-UP ----------

QUESTION: thank you for your detailed response. I will send u a photo to help me determine the best treatment.     The palms are saga.They have the black spots under the leaves. they are small raised spots.I am not sure if they are sticky or not. I will send photos.thanks so much!

Answer
Hi Melanie,

Thanks for the top ratings! From your brief description, I am quite sure scale is what your Sago palm has. Sagos are quite prone to scale. I will look for your photo and confirm after I receive it. A photo of the entire plant and its pot might also be useful.

~Will