Stephen J. Toth, Jr. and Thomas A. Melton, editors

The information and recommendations in this newsletter are applicable to North Carolina and may not apply in other areas.

Date: September 25, 2001

From: Stephen B. Bambara, Extension Entomologist

I recently received a question via voice mail about silverleaf whitefly on geraniums, but the caller did not leave a name or phone number. I think this information bears repeating to all.

To clean up a heavy infestation of whiteflies, I recommend using insecticidal soap, horticultural oil or Tame + Orthene 75S several times at relatively close intervals. Since Marathon has been labeled for whiteflies (aphids, mealybugs and leaf-feeding thrips), growers have a granular systemic pesticide for greenhouse ornamentals. If the population has a bunch of mature fourth instars (the pupae), new adults will continue to appear for a week or two in spite of the spray applications. Apply to undersides of leaves.

The silverleaf whitefly is resistant to resmethrin (PT 1200), Temik, sumithrin, oxamyl 10G, malathion, Metasystox-R and Mavrik. I also have some unconfirmed reports of possible resistance to Marathon. In Jim Baker's demonstrations, Talstar, Insecticidal Soap, Enstar II, and Tame + Orthene have worked well for whitefly control. Marathon 1% granular also provides good control. Ornamentals and Turf Insect Note No. 83 that provides a little more information on this pest. It is also available on the World Wide Web at the following site: http://www.ifas.ufl.edu/~apkweb/ncstate/whitfly.htm.

Other possible chemicals to use are: Avid, Azatin XL, Thiodan. Of course, diazinon and chlorpyrifos compounds are on their way out of use. Some chemicals may be phytotoxic on some plants.

I want to emphasize the following:

1. Orthene should be used mixed with Tame.
2. Marathon granules are not taken up immediately so other controls may need to be used while this begins to work.
3. Rotate chemicals!

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Last modified on September 21, 2001 by Stephen J. Toth, Jr.