Question
Hi Will,

Hope you can help. My grandmother gave me a hibiscus plant about 4 years ago. It seemed pretty healthy but now the leaves are drooping and some are starting to turn yellow and fall off. There are tiny, tiny white spots on the tops of the leaves and some tiny white, beige spots on the underside of the leaves. The tops of the leaves are also glazed with a sticky film which is creating a sticky residue on the floor beneath the plant and on the nearby furniture (up until now, I thought the stickiness was normal for the hibiscus because it seemed to happen every now and then). On the underside of the leaves there are also some tiny, white flies (they fly off the leave if you tap the plant). I just noticed this problem when my husband bought me some roses and within days they died. (The roses were within arm's length of the hibiscus). Upon closer inspection of the roses, I noticed they were covered with the tiny white flies. I can't figure out which plant attacked which. I suspect the pests on the hibiscus attacked the roses because the sticky floor problem has been around for several weeks (maybe months). The hibiscus bloomed all summer so I think it was relatively healthy back in August.

If you can recommend a treatment for our plant (preferably non-toxic, as we have some youngsters in the house) I would be very grateful. Thank you.

Answer
Hi Natasha,

Your Hibiscus is infested quite severely with two different pests - whiteflies and scale. The whiteflies are obvious. The scale insects appear as small raised bumps on the underside of the leaves. The scale insects secrete a sticky substance called honeydew.

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.

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.

Important: None of these should be applied to plants in direct sun or in high temps.

Whitefly eggs are found on the undersides of plant leaves where they are barely noticeable. If possible, take the infested plants outside and spray the undersides of the leaves with a moderately strong hose spray. Be thorough so as to get all of the eggs. In the process, most of the adult (winged) whiteflies will also fly off. That is why this should be done outside. The whiteflies can also be treated with Brand X or with soap and alcohol as described above.

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

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

Visit my website at  www.HorticulturalHelp.com

If you would like to e-mail me some photos, I may be able to provide some additional insights.