White Flies

(May 2009)

I have three beautiful gardenias in my yard. They bloom wonderfully every year, but my only problem seems to be white flies. I used the Bayer insecticide that you put into the root system and Malathion, but I still have a problem. Do you have any other ideas?

Imidacloprid (Bayer Advanced Tree and Shrub Insecticide) does do a pretty good job, but the results will not be instantaneous. The plants have to absorb the chemical. Occasionally a second application applied midsummer is needed for all season control. Other options include: Resmethrin, Permethrin, Talstar, and Mavrik are other options.

(June 2005)

I have recently planted three gardenias on the front of my house. These plants receive the morning sun and afternoon shade. My question is what makes the pretty green leaves turn yellow and fall off? Please help me with this problem . I am trying to make a hedge with the gardenias.

Several things can cause yellowing of gardenia foliage. Some are nutritional, or soil related, and the other can be insects. If the pH is too high, they can suffer from iron chlorosis. This condition usually causes yellow foliage, with green veins in the leaves. Although our soils are often acidic, occasionally liming or other conditions can cause a more alkaline condition. If they are planted next to a new foundation or new sidewalk, often the lime can leach out of the concrete causing a rise in pH. A soil sample can determine the pH and help you lower the pH. Another nutritional problem can be a lack of nitrogen, which can cause yellowing of the foliage. Poor drainage can also give rise to a weak and a more yellow plant. Another, and often more common problem is an insect called whitefly. Adult whiteflies often fly when the plant is disturbed, giving an almost dandruff like scattering of white. The larval and egg stages congregate on the underside of the foliage. These insects suck sap out of the foliage, and can cause yellowing and even a distortion of the leaves. Heavy infestations often give rise to a black coating on the leaves, caused by black sooty mold which builds up on the sweet honeydew given off by the insects. Whitefly is not easy to control. Systemic insecticides applied early in the season can give you some control now, or you can use Resmethrin. Other products are also available. But before you start spraying, try to determine the cause of your problem. Your county extension office is a great place to start.

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