University of Maryland Extension

Problems Controlling Whitefly

On Poinsettia:

There were some really tough whiteflies in greenhouses in Summer 2013. Two growers received poinsettias in the spring from the West Coast. One shipment came in late March for stock plant production. The other greenhouse operation received plants in April to produce tree poinsettias. In both cases the plants came in with small populations of whitefly. In hindsight, they should have refused the infested plants, but it was a busy spring.

In both cases, they treated with imidacloprid and then ignored the plants through the spring bedding plant season. The grower that introduced the plants in late March ended up applying Avid, Azatin, Azatin, BotaniGard, Sanmite, Safari, Distance, TriStar and finally, Kontos. He just obtained a reasonable control in early August since he applied the Kontos, but it took several weeks for the Kontos to really show an impact.

The second grower’s greenhouse operation treated plants May through August with wet sprays of Aria, Talus, Judo, 1% oil, Sanmite, NoFly, Endeavor, Marathon II, and Azatin. They were applying the foliar applications once a week. The whitefly population kept increasing. Two weeks ago they applied a Kontos drench. Since they applied the Kontos drench (about 2 weeks prior to my visit) the newer foliage was pretty clean, but I still found several viable 2nd and 3rd instars and a couple of adults with their mouthparts still inserted into the foliage and still alive. The older foliage (4 - 6 weeks old) had incredible populations of eggs, and all sessile stages present. I have not seen populations of whitefly like this one in a very long time. There was actually sooty mold growing on the foliage with all of the honeydew produced by the whiteflies.

The whitefly species was Bemisia tabaci. Several years ago several growers had major problems with Bemisi tabaci Biotype Q which was resistant to several classes of chemistry.

Control Options:

If whitefly populations continue to be very high, be sure to rotate chemicals at 7-day intervals. It is critical to rotate using chemicals with different modes of action to reduce the chance of developing resistance.

In trials conducted in Florida, researchers Cindy L. McKenzie1, Vivek Kumar2, Cristi L. Palmer3, Ronald D. Oetting4, Lance S. Osborne2, found that the following insecticides were most effective in controlling the Q-biotype whitefly: spirotetramat, dinotefuran, acetamiprid, and spiromesifen. In their trial, imidacloprid, thiamethoxam, pyridaben, pyriproxyfen, flonicamid, oil, and azadirachtin or hydrophobic extract of neem oil reduced whitefly populations, but not to the extent as the insecticides listed above.

1USDA-ARS, U.S. Horticultural Research Laboratory, 2001 South Rock Rd, Ft Pierce, FL 34945
2Mid-Florida Research and Extension Center, IFAS, University of Florida, Apopka, FL, USA
3Rutgers, The State University of New Jersey, IR-4 Project Headquarters, Princeton, NJ USA
4College of Agriculture and Environmental Sciences, University of Georgia, Griffin, GA, USA

Author: Stanton Gill, Extension IPM Specialist, University of Maryland
Maintained by the IET Department of the College of Agriculture and Natural Resources. © 2020. Web Accessibility

University programs, activities, and facilities are available to all without regard to race, color, sex, gender identity or expression, sexual orientation, marital status, age, national origin, political affiliation, physical or mental disability, religion, protected veteran status, genetic information, personal appearance, or any other legally protected class. If you need a reasonable accommodation to participate in any event or activity, please contact your local University of Maryland Extension Office.