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Ask Dr. Hort: 'Sooty mold' on gardenias, rusty leaves on cypress, gophers in the peanut patch

Gardenia needs neem oil to get rid of 'sooty mold'

Q: My gardenia bush has some type of growth on the branches, along with black smutty stuff on the leaves. Many of the branches are dying, and the leaves are turning yellow and falling off. Any ideas as to what is wrong? Dave Bowman

A: Your gardenia is covered with "sooty mold," which is a fungus that lives off the excrement of sucking insects (honeydew), in your case most likely whitefly. To eliminate the sooty mold, you need to control the whitefly. A biorational approach is to use neem oil weekly for one month. It is important to cover 100 percent of the plant, especially the undersides of the leaves. You will accomplish two things with one product: Peel off the sooty mold and begin control of the whitefly. Before application (following label directions) prune out any dead wood. Continue to monitor leaf undersides for whitefly larva (small whitish/green dots the size of a period) on new growth and employ spray program as needed. As the health of your gardenia improves through fertilization, your whitefly problem should decline.

Bald cypress is doing what comes naturally

Q: My cypress leaves are a rusty color. I had it sprayed for spider mites, but no improvement. What is causing this and how can I prevent the same? Irene Mullen, Ocala

A: The mystery is solved, and not to worry! The plant in question is bald cypress (Taxodium distichum), which is an incredible tree, growing from Miami to Canada and should be used more here in Florida. It is a deciduous tree (it loses leaves in winter) with fine foliage that turns yellow and then rusty brown before falling and blending into the grass. Because of the warm winter this year, deciduous plants are confused, not knowing whether to turn color and defoliate or stay green on the tree. Enjoy the rest of the colors before it goes bare, and not to fear, the foliage will be back in a couple of months.

Controlling gophers, weeds in peanut patch

Q: I planted 100 peanut plants last year for ground cover and am very pleased. My question is how to get rid of the gophers that have decided to dig in them. Will they cause any damage to my plants?I am also looking for a way to control weeds. Paul Herrick

A: What a good lookin' patch of perennial peanut, Arachis glabrata! If the gophers aren't bothering the patch, let them be. They do aerate the soil, but if overdone, roots will die. Water down tunnels on a regular basis, and if the gophers become troublesome call a professional trapper; gopher gadgets will drive you insane and still not work.

As far as the weeds, you need to identify the intruders by type — broadleaf, sedge or grass. Broadleaf weeds will need to be hand-pulled because herbicides labeled to kill broadleaf weeds will also kill your peanut. Sedges can be controlled with the herbicide Image, and grassy weeds can be controlled with the herbicide Vantage. Image and Vantage are considered "selective herbicides" because they target one type of weed without harming the ornamentals involved. It is very important to follow label directions closely so as not to harm the ornamentals.

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. Email him at [email protected] or mail questions to HomeLink, Features Department, Tampa Bay Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned.

Ask Dr. Hort: 'Sooty mold' on gardenias, rusty leaves on cypress, gophers in the peanut patch 04/21/12 [Last modified: Saturday, April 21, 2012 4:31am]
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