December 2005

Q Biotype Whitefly: The Good News By Lin Schmale

Good news: Santa Claus does exist after all! Jim Bethke, working with Frank Byrne and Rick Redak, all of the University of California, Riverside, has written an article (see page 18) you must read. Their research, supported in part by the Floriculture & Nursery Research Initiative and IR-4, has definitively shown that some chemicals will work against the newly discovered Q biotype whitefly. And more research is ongoing that will add even more information.

The Background

You probably know that earlier this year discovery of the sweet potato whitefly Q biotype threatened to send panic throughout the ornamentals, cotton and vegetables industries. Although the learning curve for methods of control has been steep, scientists have learned that the problem with the Q biotype whitefly is its resistance to many of the chemicals commonly used to control the common B biotype. Therefore, scientists in the United States were unsure exactly which chemicals available here would control the Q. The affected industries needed knowledge about where Q was present in the United States and experiments to show which chemicals might control the pest.

Quarantines were initially imposed by California and Arizona (subsequently lifted). To avoid a crisis, leaders of the three industries got together and agreed to form the National Ad Hoc Whitefly Taskforce. It would be led by representatives of the three industries and facilitated by APHIS. The Taskforce incorporates leading scientists from around the country, as well as federal and state regulatory officials. It has been meeting since last spring, focusing on survey efforts by the states, research and grower education. The "Technical Advisory Committee," a subgroup of the Taskforce, co-chaired by Lance Osborne, University of Florida, includes leading scientists and is discussed on page 26.

Growers must feel comfortable about getting samples tested without threat of quarantine, we argued. If a grower is having a whitefly problem, it's important to find out about it and get it under control. But if growers are afraid of being quarantined and having to destroy crops, they are not likely to report a problem. The problem would get worse as it is ignored, and the whiteflies would proliferate and disperse, defeating our purpose. So the ornamentals industry has put an especially high premium on grower awareness. The trade press of the ornamentals industry has been especially helpful in getting the word out to growers. SAF and the American Nursery & Landscape Association joined together with Osborne and other key scientists to issue a "best guess" document in late August, giving growers the best knowledge scientists had about how to control B and Q whiteflies.Growers have shown an excellent response — and must continue to respond. Thanks to growers all over the United States who have gone to their university extension specialists or county advisers or sent samples directly to one of the labs authorized to test for B and Q whiteflies, we now have a much better picture of where the Q whitefly is. Growers are adding knowledge to that picture every day as they continue to find and report problem or resistant whiteflies. Key states have also conducted surveys under the guidance of the Taskforce. As a result, we know that the Q has been found in states from Oregon to New York, from Michigan to Florida. In short, it is probably quite widespread.

Science now provides new information about tools to fight the Q whitefly. The Floriculture & Nursery Research Initiative and IR-4 quickly provided funding for new efficacy trials to determine which of our existing and new chemicals might ç be effective against the Q biotype. Initial results of that research are reported in Bethke's article, with specific recommendations on which chemicals work best. That research is continuing, and more information will be provided to growers just as soon as it becomes available.

What To Do Now

I wanted to pass along a few pointers to you, the growers. The following will help you determine what to do during this incident.

• Look at your crops to make sure you are not having whitefly problems. You may think you aren't, but remember, if you develop a problem late in the poinsettia season, it can be much more difficult to control. Scouting is essential. Make sure your spray programs are working.
• If it turns out you are having some problems — even minor ones — with your spray programs, immediately contact your county adviser, county extension agent, propagator's support team or other expert adviser, and you should also have the whiteflies tested to determine which biotype you are dealing with.
• Then, adjust your spray programs according to the latest available research (see page 18).
• And continue to watch for updates as research continues.There is no reason to panic. In fact, there is less reason to panic today than there was earlier this year. It is important, however, to know your enemy.

As you know, whiteflies have a very wide host range. Just because we are exiting the poinsettia season does not mean you are clear. Additionally, a whitefly control problem does not necessarily mean a grower has the Q biotype. Lack of control could mean poor spray coverage or a B biotype population that is developing resistance. But it's important to know with what you are dealing, apply chemicals appropriately and rotate modes of action.

Additionally, you should review all aspects of your IPM program concerning whiteflies. Scouting is essential. Good sanitation is essential. Get rid of weeds, old plants and anything else that might serve as a refuge for the insects you're trying to get rid of. And if you have difficulty controlling whiteflies, please contact your local county adviser, extension agent or propagator's advice team and submit a sample for biotyping. The results will remain proprietary to your business and confidential, if you so request.

Participate with other ornamental growers, producers of cotton and vegetables, and the Whitefly Taskforce in the important advances being made against this pest — if you do not, you are part of the problem!