Q Biotype Whiteflies Found

April 1, 2005 - 13:41

Q Biotype whiteflies, a highly resistant strain of whitefly that is indistinguishable from silverleaf whitefly, have been found on poinsettia in Arizona. Details about this new pest and its possible impact on U.S. floriculture are still being sorted out, but the following is what we could track down right now.

Because of an ongoing research project to test whitefly resistance levels, researchers from the University of Arizona Extension Arthropod Resistance Management Laboratory were collecting whiteflies on a poinsettia at a retail outlet in Tucson, Ariz. Once in the lab, it was discovered that whiteflies collected at this location were highly resistant to insecticides. Further testing, which was confirmed by three separate labs, identified the strain as the Q Biotype of Bemisia tabci. Early indications are that the infested poinsettia originated in California.

Two species of whiteflies are common pests of greenhouse crops worldwide, the greenhouse whitefly (Trialeurodes vaporariorum) and the sweet potato or silverleaf whitefly (Bemisia tabaci). In the late 1980s, a more difficult-to-control biotype of B. tabaci spread rapidly in the United States, resulting in widespread problems with whitefly damage and more severe problems with plant viruses. In the Mediterranean region, where our B Biotype and the Q Biotype co-exist, the Q Biotype has been associated with particularly intensive resistance to insecticides and related severe virus problems. For this reason, the Q Biotype is the subject of extensive studies in Europe. Until this report from Arizona, the Q Biotype had never been found in the United States.

The Q Biotype originates in the Mediterranean region and has been associated with whitefly control problems in Spain, Israel, Morocco and Egypt. It has recently also been detected in China, Japan and The Netherlands. Q Biotype so closely resembles the B Biotype that the two are indistinguishable even under a microscope. The only way to tell the difference between the two biotypes is through extensive chemical and DNA testing. University of Arizona researcher Judy Brown has pioneered development of these tests and collaborated with detection of the Q Biotype in Arizona.

The immediate significance of the Q Biotype is that it has unusually low susceptibility to many of the key insecticides currently used to control whitefly. University of Arizona researcher Tim Dennehy’s laboratory has tested the resistance of Q Biotype against pyriproxyfen (Distance) on eggs and imidacloprid (Marathon), thiamethoxam (Flagship) and acetamiprid (Tristar) on adults.

As you can probably imagine, there are many outcomes to this case that may arise. There is talk of a quarantine on poinsettias, and perhaps all host plants, from Arizona and California; there is concern that the Q Biotype will spread throughout the United States; and there is speculation about what chemicals can be used for control.

Problems have arisen in southern Europe due to the lack of control methods. “Most of the materials in southern Europe have been lost,” said Lance Osborne, professor of entomology at the University of Florida “Some of the neonicitinoids are having trouble with the exception of the (newly registered) Safari.”

The good news is that University of Arizona researchers have no indication that the Q biotype has become established in field systems in Arizona. Efforts are currently underway by regulatory agencies to track the infested plants back to the producer. “It is too early to say anything about how widely the Q Biotype is distributed in the United States,” said Dennehy. “Hopefully we have detected it early. We were able to notify the USDA and Federal agencies within three months of making the collection.”

“We have known for 2-3 years that a resistant strain of Silverleaf Whitefly had emerged in Europe,” said Jim Barrett, professor of floriculture at University of Florida and GPN’s consulting editor. “We can hope that this particular outbreak is isolated and does not become established; however, the fact that this Q Biotype has been located now in several other regions of the world, indicates that it is spreading and that it will only be a matter of time before it does become established in the United States. Due to our warmer conditions this whitefly could become more widespread and more of a problem for U.S. growers than it is in Europe. If this infestation from last fall does become established hopefully we can develop good management programs based on what has worked in other regions. For growers, especially in the West, who develop whitefly problems this spring, it is important to monitor population levels more closely than in the past. Growers should not just treat with a standard chemical and assume the problem is solved.”

Osborne agrees with Barrett. “Growers need to be very careful about the material they’re buying in… Inspect, practice good IPM (if it comes in with whiteflies — even if just a few — I would probably think twice about accepting because no matter what biotype it is you’re asking for problems.) Don’t bring anything in that’s dirty in the first place.”

We will definitely keep you informed as we find out more information. We will be updating you on this story in future issues of GPN Weekly and will have a feature-length article as soon as possible in GPN.

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