A new study shows growers may be keeping a watchful eye on the Q-biotype situation, but many have treatment practices in place that may inadvertently encourage resistance, not fight it.
The Q-2006 study was a collaboration of key industry organizations: OFA–an Association of Floriculture Professionals, Society of America Florists (SAF), American Nursery and Landscape Association (ANLA), Florida Nursery Growers and Landscape Association (FNGLA), USDA’s IR-4 and Valent Professional Products.
“There’s a lot of talk, and frankly, some fear-driven confusion in the industry about Q-biotype,” says Dr. Joe Chamberlin, field market development specialist with Valent. “Some growers are worrying too much; some may not be taking it seriously enough. The study collaborators saw this survey as a great opportunity to understand what is going on in growers’ minds, and help get the smartest scouting, testing and treatment practices in place to address Q-biotype and overall resistance.”
Dr. Lance Osborne, University of Florida and co-leader of the industry’s Q-biotype Task Force, and Jim Bethke, University of California-Riverside, reviewed the study results and offered recommendations to growers at an OFA Short Course meeting in July.
“Many results were as we expected,” Osborne says. “Overall, growers are doing a good job in managing their operation against resistance. But several trends emerged that showed us there are still everyday practices that could be improved.”
Manage Q, Manage Resistance
According to the Q-2006 study, more than 85 percent of respondents claimed they were “somewhat” or “very” concerned about Q-biotype. Though researchers want growers to pay attention to the Q-biotype issue, many see its emergence as an example of the greater resistance management issue facing the industry.
“Today we have a Q that is manageable, but if growers don’t put resistance management at the center of their treatment program, we could be dealing with a more resistant Q tomorrow, or even a different and more resistant biotype,” Bethke says. “Growers shouldn’t panic or be overly concerned. Just pay close attention to unusual outbreaks and know where to go for information and which resources are best equipped to help your operation.”
Researchers encourage growers to stay up-to-date on any news about the Q-biotype through trade journals and Web sites dedicated to the issue.
Scout And Test Today To Keep Problems Away
Scouting for unusual outbreaks can help growers improve their resistance management practices without significant change to their operation or costs.
More than 80 percent of respondents said they scout for whiteflies at least weekly (54 percent weekly, 28 percent daily)–a practice applauded by both researchers.
“A good weekly scouting should be manageable within most operations,” Osborne says. “Most whitefly populations do not develop significantly over the course of seven days, which allows you to keep a good handle on emerging pests.”
The researchers were concerned, however, with the nearly 20 percent of growers who stretch their scouting efforts beyond the one-week mark. He encourages scouts to stay dedicated to their tasks and to check at least weekly for whitefly activity.
And both researchers agree: the best scout is well trained–often by university Extension programs–and in contact with the plants daily. When scouting for whiteflies, trainers encourage scouts to disturb the plant to encourage flight and be sure to check the underside of the leaves where both the adult and nymph whiteflies reside.
Since it is impossible to visually differentiate among whitefly biotypes, researchers agree that proper testing is a valuable tool to help growers determine whether the Q-biotype is the root cause of a whitefly control problem. Fewer than 10 percent of respondents said they would test for Q-biotype at the first signs of resistance; many (35 percent) would simply increase their insecticide use. “Without proper testing, I can’t tell the difference between Q and other strains,” Osborne says. “I’m confident scouts can tell apart the major whitefly species, but it’s almost at the point we want growers to assume they have a resistant strain of the whitefly, get it tested for Q-biotype immediately and treat it appropriately.”
Use Proven Products In Rotation
As the seasons begin for such highly susceptible crops like poinsettia, what are the best treatment options for the grower hoping to prevent or fight Q-biotype? Both researchers recommend growers work closely with a trusted source to choose a rotation of treatments and chemistries that may be used throughout the entire crop cycle.
Many growers seem to be embracing the idea of rotation. Nearly two-thirds (64 percent) of respondents claim they used the same chemistry no more than three times within a given crop cycle. Bethke recommends a maximum of 21 consecutive days with the same chemistry. He says sometimes resistance is further encouraged by growers who mistakenly think they are changing modes of action when they rotate products.
“Just because you are rotating products, don’t assume you are rotating chemistries,” Bethke says. “Work with an Extension agent to ensure you are incorporating a full range of chemistries and maintaining good management practices.”
Most respondents in the study ranked “overall efficacy” (77 percent) and “length of residual” (66 percent) as their top attributes when selecting a treatment for whiteflies. Bethke says a thorough and complete kill is critical in whitefly treatment, but growers should also consider translaminar activity–an important attribute when treating whiteflies that dwell on the underside of leaves.
“A translaminar product or a good systemic should be one of the first products they should look for to effectively address whiteflies,” Bethke says.
Chamberlin says university trial data should serve as the cornerstone to developing a sound IPM program. He encourages growers to look to products that have consistently performed well in university trials.
“Several products have worked very well against the Q in university trials,” says Chamberlin. “Safari has been highly effective as a soil drench when tested against Q on poinsettia, and a number of products have been consistent performers when applied as foliar sprays, including Avid, Judo, Safari, Sanmite and TriStar. As always, coverage is key with foliar sprays, and products with translaminar activity should be considered in dense crop canopies.
“The most important thing is to not rely on that one best product for control of Q, but to instead rotate products with differing modes of action. Fortunately, the products I have mentioned are drawn from four different IRAC mode of action classes. This means that at the present time, growers are in a good position to put together an effective resistance management program for Q.”
Growers can see the full university trials of Q-biotype treatments at http://www.mrec.ifas.ufl.edu/LSO/bemisia/bemisia.htm