A team of researchers offers its best guess for management of the Q-Biotype whitefly, Bemesia tabaci, on poinsettias. Stay tuned for more whitefly-related coverage in Greenhouse Grower.
PESTICIDE recommendations have been developed for each of the following four poinsettia growth phases:
* Propagation phase - the cuttings are on the mist bench.
* Recent transplant phase - rooted cuttings have been transplanted, but not yet pinched. Roots do not yet extend well into potting media and plants will not be efficient at taking up soil-applied systemic insecticides at this time.
* Growth phase - transplants pinched and roots extend well into potting media and can efficiently take up soil-applied insecticides. Bracts do not yet show color. Adequate whitefly control is critical during this time.
* Color phase - bracts show color.
Pesticide options are most limited during phases one and four due to either frequent irrigation, phytotoxicity concerns or both.
Q-Biotype Pesticide Program
Propagation. Pesticides may be washed off plants early in the mist cycle and phytotoxicity may be an issue with some products. Pesticides may be more effective after the mist frequency is reduced. Recommended products include:
* Foggers
* Beauveria bassiana
* Avid (sometimes used in combination with acephate or a pyrethroid such as bifenthrin or cyfluthrin)
* Neonicotinoid spray with translaminar and systemic activity.
Recent transplants. Foliar sprays are most effective during this phase. Recommended products include:
* Abamectin
* Azadiractin
* Beauveria bassiana
* Buprofezin
* Endosulfan
* Flonicamid
* Kinoprene
* Novaluron
* Potassium bicarbonate
* Pymetrozine
* Pyridaben
* Pyriproxyfen
* Pyrethroid + Acephate
* Pyrethroid + Azadiractin
Growth phase. A single soil drench or granular application with a neonicotinoid is strongly recommended within one to two weeks after pinch. Soil treatments before or after this time may be less effective. Systemic activity may be greater with more water-soluble products. Important note: Pots should not be drenched during the first week after application or some insecticide may be washed out of the media before being absorbed by the roots.
Recommended products include:
* Neonicotinoid soil treatment
* Dinotefuran
* Thiamethoxam
* Clothianidin
* Imidacloprid
After drenching, apply foliar sprays as needed if whiteflies are present. Avoid repeated application with a single mode of action (products with the same number in the attached chart). If plants have received a neonicotinoid drench, do not spray with a neonicotinoid during this phase if at all possible. If necessary, make only a single spray just prior to bract color.
Recommended products include:
* Foliar spray rotations as needed
* Insecticidal soap
* Beauveria bassiana
* Horticultural oil
* Potassium bicarbonate
* Spiromesifen
* Abamectin
* Azadiractin
* Endosulfan
* Acetamiprid
* Dinotefuran
* Clothianidin
* Thiamethoxam
* Imidacloprid
* Flonicamid
* Kinoprene
* Novaluron
* Potassium bicarbonate
* Pymetrozine
* Pyridaben
* Pyrethroid + Acephate
* Pyrethroid + Azadiractin
Color phase. Control of whiteflies during this time is hard due the difficulty of achieving effective under leaf spray coverage and the lack of labeled products. Therefore, pest management efforts should be concentrated before bracts begin to show color. Recommended products include:
* Foggers
* Any other product whose use is not restricted by the label.
During the period from pinch to color formation use products with a nonspecific mode of action (soap, oil, Potassium bicarbonate, Beauveria) as often as possible, but only if plant safety is first demonstrated. As with all pests and pesticides, proper application and coverage is essential to obtain the best results.
Whitefly Scouting And The "Best Guess" Pesticide Program
A rigorous and regular scouting program is the foundation of any IPM or resistance management program for pests affecting floricultural crops. Scouting is especially critical for the management of the Q-biotype of Bemisia tabaci on poinsettia, and its development of pesticide resistance.
While most poinsettia growers profess to follow an IPM program, many do not employ a scout. However, if growers do not scout, they will be unlikely to detect and identify pest problems early in the infestation cycle. The end result will be calendar spraying and/or the need for "curative" control of established pest populations. Calendar spraying can result in unnecessary (and costly) pesticide application, and it may also accelerate the development of pesticide resistance. The latter is especially undesirable for a pest like the Q-biotype, which is already noted for its tolerance or outright resistance to a number of insecticide classes.
Finally, once pest populations are established, they are much more difficult and costly to bring under control, and pesticide options can be more limited. Find an introduction to scouting at: www.mrec.ifas.ufl.edu/LSO/SCOUT/INTRO.htm.
It is important for poinsettia growers to recognize that scouting is a critical component of whitefly management regardless of biotype, and that without a rigorous scouting program, they will be unable to take full advantage of the "Best Guess" pesticide program that is presented above. For example, several pesticides (ex. IGR insecticides that have strictly contact activity) listed in the program are much less effective once pest populations are established, and/or will take longer to work. In addition, once a poinsettia begins showing color, pesticide options are very limited due to labeling restrictions. Therefore, it is vital for poinsettia growers to be proactive with respect to whitefly management, and to initiate control programs when pest populations are first detected. This requires scouting.
Poinsettia should be scouted at least weekly for adult and immature whiteflies. Scouts should tag or map the location of infested plants so these plants can be evaluated after the application of pesticides or other management tactics. This will allow growers to determine how effective their pest management program is against whiteflies. If control is less than desirable, this information will allow growers to investigate the root cause of the control failure. In many cases, control failures have nothing to do with resistance, but instead result from inadequate levels of pesticides reaching the pest. This is most often due to inadequate spray coverage or improper use of soil-applied insecticides (ex. application before roots are established, or excessive leaching during the first week after application). Scouts can be instrumental in detecting poor application technique.
Scouts can also detect control failures that result from reduced tolerance of whiteflies to a given pesticide. The first sign of insecticide tolerance is a reduction in residual activity, and the consequent need for more frequent pesticide application. If whiteflies are developing a tolerance to an insecticide, early detection by scouts will allow growers to substitute or incorporate pesticides with different modes of action - before pest populations reach unmanageable levels.
More To Come
We will develop a more detailed document on scouting poinsettias and post it to the Bemisia Web site (www.mrec.ifas.ufl.edul/LSO/bemisia/bemisia.htm).
About the authors: Contributors to this article, in alphabetical order, are: James Bethke, Luis Canas, Joe Chamberlin, Ray Cloyd, Tim Dennehy, Jeff Dobbs, Scott Ferguson, Dan Gilrein, Richard Lindquist, Scott Ludwig, Ron Getting, Lance Osborne, Cristi Palmer and John Sanderson.
If you have any comments or suggestions concerning the information contained within this document, please contact one of the contributors or e-mail Dr. Lance Osborne; lso@ifas.ufl.edu.
For more information on Q-Biotype whitefly, please visit www.safnow.org. This article was reprinted with permission from the Society of American Florists and the American Nursery and Landscape Association.
Copyright Meister Media Worldwide Nov 2005
Provided by ProQuest Information and Learning Company. All rights Reserved
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