What’s In a Letter?
The letter in question here is Q. What does it mean to have Q-Biotype whiteflies instead of B-Biotype whiteflies. The quick answer is no one really knows yet, but it’s the long answer that the industry has been grappling with for the past few weeks.
If you’ve been reading GPN Weekly, our e-newsletter, (not a subscriber? go to www.gpnmag.com to sign up) then you know that the past few weeks have seen a flurry of speculation about the discovery of a “new” whitefly in Arizona and California (turn to page 10 for more information). The so-called Q-Biotype whitefly is a very close cousin to the standard silverleaf whitefly, known as the B-Biotype. In fact, the two look exactly the same and can only be distinguished by molecular analysis.
The big concern about the Q-Biotype is a report that this subclass is less susceptible to standard chemical controls (Marathon II, Flagship and TriStar) than other subclasses. Granted, that sounds pretty intimidating — those of you around when silverleaf whitefly first hit the industry remember what it was like not to have any chemicals to control this pest — but on closer inspection the situation is really not as bad as it seems.
A Few more facts
Our fear of Q-Biotype whiteflies comes from resistance research conducted at the University of Arizona and reports from Europe, where Q-Biotype is common. The Arizona research, which is actually very interesting stuff, relies on a recently developed molecular test that allows whiteflies to be divided into biotypes. Before this test was developed, we just called everything a silverleaf whitefly, which made me wonder how we know Q-Biotypes have not been in the United States for a long time. Maybe they have been here for years, but we have just not known it because we were not able to identify them. So, if they have been here for years, and we have not had major control issues, maybe this is not so bad.
Additionally, I’ve heard from several different sources that only a few Q-Biotypes were found at the suspect facilities. Instead of a large, established Q-Biotype population, there were only a few mature adults collected. With such a small population, I can’t help but believe that whatever control measures were used by the growers worked fairly well. Most growers I know don’t expect to kill every insect and would consider that much control a resounding success.
This is, in fact, what I have been hearing from people who spend a lot of time in Europe. Namely, that the Q-Biotypes, while being less susceptible, are controllable. Europe is not overrun with whiteflies; they just have to work a little harder to get control.
What does it mean?
First and foremost, the above information will hopefully make everyone a little less nervous about this “new” pest threat. While there have been some quarantines issued, as of press time, no one was under quarantine, and it’s debatable whether or not this is actually a quarantine-able pest (do USDA guidelines allow resistance to be used as a determining factor?).
Second, we have a number of highly effective products for control of normal, B-Biotype whiteflies. The reports are mixed about the effectiveness of these products on Q-Biotypes. Word-of-mouth from Europe is that all products are effective but require higher rates and/or have less residual activity.
We are learning more about this pest all the time. So if you want an update or for more background information go to www.gpnmag.com and search the news archive.
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The letter in question here is Q