Question
Hi Mr. Creed,   I just discovered a scale insect infection on my spider plant.  I will spend some time fighting it but as I live in New Orleans I can grow another one in a week.  My question is that right next to my spider is a large Yucca tree.  Is has been very healthy but I just re-potted it and a few of the leaves turned brown.  The leaves did have that "honeydew" on them.  Is the Yucca also susceptible?

Thanks

Answer
Hi Pat,

Yes, Yuccas are another preferred host of scale insects. If the leaves have that tell-tale stickiness on them, it is very likely to be scale insects. I suggest that you treat them right away before the spread further.

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 100ffective 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.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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