Question
I have a hedge about ft. tall of Orange Jasmine that has been healthy but now is showing signs of yellowing. I have never fertilized it but I'm sure it needs to be. The leaves look clean, but there are white fly flying around. When should I fertilize it and with what? Thank you for your help.

Answer
I would think the white flies are the problem. Whiteflies damage plants by sucking out plant juices. Because large amounts of sap can be removed, primarily by the developing nymphs, heavily infested plants can be seriously weakened and grow poorly. Leaves often turn yellow, appear dry and drop prematurely.  Also, because whiteflies suck out more plant juice than they can digest, the excess is excreted as a sweet, sticky substance called honeydew. The honeydew covers leaf surfaces and acts as a growth medium for a black, sooty mold. Both the removal of plant juices and the presence of the black, sooty mold growing on the honeydew can interfere with photosynthesis.

I would spray the hedge with an insecticide. It many cases it has been difficult to control whiteflies with insecticides because they have developed resistance to some chemicals. Because of this resistance, a certain product may work well in one area but not in another. Resistance may be delayed by alternating the types of chemicals used. In addition, the egg and non-feeding pupa stages are generally not as susceptible to insecticides as are the adults and nymphs. Consequently, eradication of a whitefly population usually requires four to five applications of a registered insecticide at five- to seven-day intervals. Be sure that the applications are made to the lower leaf surface, and apply as soon as whiteflies are detected. Do not wait until populations become severe.

Here are several insecticides that will work for white flies. Check with your local nursery/garden type store for these. Ortho Orthene Systemic Insect Control, Ortho Isotox Insect Killer, Spectracide Lawn and Garden Insect Control, Ortho Malathion 50 Plus Insect Spray