In May 2016, for the first time the pesticide resistant silverleaf whitefly (Bemisia tabaci) Q-Biotype has been found established in Florida (Palm Beach County) landscapes.  Another genetically different whitefly that looks exactly the same, called the B-Biotype came into Florida around 1996 and created havoc for nursery poinsettia and commercial vegetable production by displacing the original “A-Biotype.”  Since then, the neonicotinoidinsecticides helped manage it and other whiteflies.

The Q-Biotype (we will just call it Q whitefly for the remainder of this document) developed in the Mediterranean region of Europe likely due to their intensive form of vegetable production.  All of the biotypes of silverleaf whitefly look exactly alike.  They can only be differentiated by genetic testing – and sometimes by their sensitivity to, or tolerance of certain insecticides.  The genetic tools were not available in the mid-1990’s to reduce the confusion about the taxonomy of these insects back then.  Old names like sweetpotato whitefly and Bemisia argentifolii can still be found in documents available on the web. 

As of June 1, 2016, the Q whitefly has been positively identified in landscapes in Palm Beach Gardens, Palm Beach, Boca Raton and western Boynton Beach.  That is a broad area and implies that the Q whitefly is probably more widespread throughout the county – although, we will have to wait and see on that.  Interestingly, only B-Biotypes have been found so far in Broward and Monroe Counties, although they are also experiencing unusually high silverleaf whitefly control problems in spots.  Also of note is that Q whitefly transmitted viruses have been devastating vegetable production in some areas of the world.  Silverleaf whitefly has greater than 900 known host plants and can transmit more than 100 plant viruses.  So far, locally we have seen the Q whiteflies mostly on hibiscus and crossandra in landscapes.  The whitefly transmits at least two common tomato viruses in Florida, and one common pepper virus.  In fact, if you grow garden tomatoes in Palm Beach County, you probably have had tomato yellow leaf curl virus transmitted the B-Biotype on them in the past.  Viruses cannot be treated in vegetables, and must be controlled by managing the insects and destroying the plants.  Thankfully, we are at the end of tomato and pepper commercial production for this season, but you can see the implications for next season if limited effective insecticides are available for this difficult to manage pest.

Recommendations for landscape management are being developed and evolving.  Residents can use repeat applications of insecticidal soaps or oils to obtain some control.  Be sure to completely cover all leaf surfaces and avoid spraying during the hot parts of the day.  If you are using other common insecticides and still not getting control, feel free to contact our Master Gardener Hotline during normal business hours, Monday through Friday excluding holidays at 561.233.1750 or email mgardenfwd@pbcgov.org  The Master Gardeners can also help you identify if you actually have silverleaf whitefly, or some other insect.

Websites for Additional Information
Palm Beach Whitefly Task Force: http://www.pbcgov.com/coextension/horticulture/whitefly