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Whitefly Management Program_2011
Q Biotype Whitefly Finds in North America
30 May 05
4 July 05
8 Sept 05
23 Sept 05
28 Sept 05
29 Sept 05
13 Oct 05
15 Oct 05
18 Oct 05
28 Oct 05
2 Nov 05
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3 Nov 05
8 Nov 05
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17 Nov 05
18 Nov 05
9 Dec 05
9 Dec 05
3 Jan 06
5 May 06
23 Mar 07
21 Sept 07
3 May 2010
GET YOUR WHITEFLIES
The following laboratories have agreed to receive
whitefly samples and determine biotype. The results belong to the
sender. We would, however, like to request that the following
information be available to the Whitefly Taskforce:
• Date collected
> ornamental greenhouse
> vegetable greenhouse
> ornamental outside or open structure
• Location: at the very least we would like State and county.
• Control history if possible:
> pesticides used
> control or failure
There are a number of specifics concerning how one collects a sample
and preserves it for evaluation. For these specifics, scheduling you MUST contact Dr. McKenzie.
Cindy McKenzie, Ph.D.
USDA, ARS, US Horticultural Research Laboratory
2001 South Rock Road
Fort Pierce, FL 34945
HOC WHITEFLY TASK FORCE:
Federal and State Regulatory Agencies
Scientific Technical Working Group
Click here for a PDF version.
TO ORNAMENTALS GROWERS
AD HOC WHITEFLY TASK FORCE
early reports, 2011 may be another challenging year for
whitefly management. Whiteflies have been detected in some rooted cuttings
shipments, and hot dry conditions have promoted a greater
than normal buildup of whiteflies on field crops in parts of
Hoc Whitefly Task Force, made up of state and federal
regulators, representatives of the ornamentals, cotton and
vegetable industries, and leading scientists, has been
working together to develop effective whitefly management
programs since 2005. The success of this effort has serious economic
agriculture, and depends in
part on you – the ornamentals grower.
whitefly management program must have two goals. First, of
course, is to help growers produce a high quality, salable
crop for the final consumer. Second, but of equal
importance, is preserving the chemical tools that
agriculture uses to manage whiteflies. If we do not maintain the viability of effective
chemical tools, it will be difficult for many growers to
produce a salable crop. Consequently, the wise use of chemicals, through a
scientifically based IPM program, is essential in this 21st Century.
has seen, and is suffering from, the
results of overspraying. Insecticide misuse in the
may result in
silverleaf whitefly populations that cannot be controlled. It is important to remember that the Q-biotype
whitefly is already resistant to a number of products
commonly used. Chemical overspray could easily lead to B-biotype
Force asks you to collaborate with us in this effort. It’s not just about the challenges posed by the
about avoiding resistance development in any whitefly
should commercial growers be doing?
1. Scout – essential. Inspect your crops at least weekly. Don’t let the whiteflies get ahead of you, or your
treatment options will be more limited.
2. Exclude or isolate. If at all possible, try to exclude whiteflies from
your growing facility with screening material, and if
possible, isolate the facility so that workers have to enter
through an anteroom.
3. Practice good sanitation – essential. Keep weeds down, maintain good growing practices.
4. Inspect incoming shipments, and isolate if
necessary. All of the major propagators are cooperating in this
program, so you should not be receiving undue numbers of
whiteflies. Because zero-tolerance is NOT the goal for anyone, you
may see a whitefly or two when your shipments arrive. That’s normal, and means that your propagator (or
rooting station) is probably following good management
practices. However, if you see many whiteflies on incoming
shipments, keep those shipments separate from your other
crops until they have been treated. And contact your propagator or rooting station - inform them about the situation. Ask whether they are biotyping their whiteflies, if
they are monitoring resistance levels in their whitefly
populations, and if they are following the Task Force’s
recommended Management Program
5. Watch your neighbors’ fields. If you’re near cotton or vegetable fields, you may
see whiteflies migrate to your greenhouse at the end of
their season, and you’ll have to deal with it. If you know when those seasons are, you’ll be better
6. Study and
implement the “Management Program for Whiteflies on
Propagated Ornamentals” recommended by the Task Force. It’s available at http://www.mrec.ifas.ufl.edu/LSO/bemisia/bemisia.htm. This program is based on the best scientific data
developed to date by the Whitefly Task Force scientists. Do not rely on just one or two effective products,
but instead integrate products with different modes of
action to decrease the potential for developing resistance.
7. If you have control problems: contact your propagator, your local extension agent
or university expert. Follow our “Whitefly Management Program”, and get
your whiteflies biotyped. The biotyping process is fast, and information will
be kept absolutely confidential. Knowing which biotype you are dealing with will help
you choose the most effective control products. (The Management Plan provides a list of addresses to
which samples may be sent for biotyping.)
the potentially impacted industries, federal and state
governments, and scientists have cooperated in the
aggressive, cooperative whitefly management effort to help
growers produce a salable crop and minimize the likelihood
of developing resistant whiteflies. You are an essential part of that effort.
REMEMBER: Q-BIOTYPE WHITEFLIES ARE A DOCUMENTED THREAT, BUT
THERE IS ALSO EVIDENCE THAT B-BIOTYPE ARE DEVELOPING
RESISTANCE AS WELL. Only by working cooperatively, wisely, and together can agriculture solve this problem.
DON’T BE PART OF THE PROBLEM: BE PART OF THE SOLUTION!
Don't forget that management doesn't end once you
ship! You should make very sure that you take appropriate
actions to eradicate any residual whitefly populations while you
have the chance!
Whiteflies have long been considered a major pest of ornamental
crops. Until 1986, the primary pest species was the greenhouse
whitefly (GHWF), Trialeurodes vaporariorum (Westwood). In
1986, Bemisia tabaci (Gennadius) was found attacking an array
or ornamental plants in Florida greenhouses. Scientists in Florida
soon realized that this species was causing damage different than
any ever attributed to whiteflies. This damage caused many plants
to show signs of being infested because the plants turned yellow,
white or silver depending on the specific host plant. Because
various squash species tuned silver when infested with the B-biotype
(also known as Bemisia argentifolii Bellows & Perring) this
biotype was given the common name, silverleaf whitefly (SLWF).
Throughout the following discussion we will refer to this whitefly
as either the B-biotype of Bemisia tabaci or SLWF.
The Q biotype--In
March 2005, Dr. Tim Dennehy (University of Arizona) reported the
detection of the Q-biotype of Bemisia tabaci. This detection
came after testing whiteflies collected from poinsettia in a retail
outlet. These whiteflies were collected in December of 2004 as part
of a pesticide resistance monitoring program in Arizona. Most of the
samples had been from cotton and other crops, poinsettia and
ornamental crops were not the primary focus of this monitoring
program. Drs. Judy Brown, Tim Dennehy (University of Arizona) and
Frank Byrne (University of California) independently verified the
whitefly as being the 'Q-biotype'. This is the first time this
particular strain has been found in the United States. The Q-biotype
is thought to have originated from the Mediterranean region and has
been associated with whitefly control problems. Dr. Dennehy
determined that the strain of whiteflies collected from the
poinsettia (Poinsettia-04) can be characterized as being virtually
immune to the IGR pyriproxyfen (Distance), having strikingly reduced
susceptibility to the IGR buprofezin (Talus) and a reduced
susceptibility to the neonicotinoids insecticides imidacloprid
(Marathon or Merit), acetamiprid (TriStar) and thimethoxam
At this point in time, this strain has not been tested
for susceptibility to the other materials registered for whitefly
control in ornamentals. It must be noted, that this information
is generated using laboratory bioassays and that no field efficacy
work has been conducted to determine how these data relate to
controlling the Q-biotype in the field, at least in the United
States. This biotype is known to have resistance to
pyriproxyfen (Horowitz et al. 2003), buprofezin and reduced
susceptibility to the neonicotinoid insecticides imidacloprid and
acetamiprid in other regions of the world.
Description and Biology
The greenhouse and silverleaf whiteflies are
the primary whitefly pests of greenhouse crops. Banded-winged and
citrus whiteflies are also found in greenhouses but usually do not
reproduce and develop damaging populations. Whiteflies, when
compared to other pests of ornamentals, have a long life cycle,
ranging from 2.5 to 3 weeks up to 2 months under cooler conditions.
Adults are moth-like and covered with white, waxy powder. Adult
female whiteflies are about 1/16 of an inch in length and
deposit about 50 eggs in cool environments and up to 400 eggs at
higher temperatures. Consequently a whitefly population can reach
very high levels in a few generations at higher temperatures. Eggs
are inserted on end upon a short stalk on the underside of leaves.
The eggs are whitish to light beige but darken to a dark blue or
purple before hatching. The immature stages resemble miniature
scale insects. They are flat and oval, glassy to opaque, light
yellowish or greenish, and often provided with a fringe of wax
filaments. Older immatures tend to be darker and either cream or
yellow. Newly hatched immature crawlers move around on the leaf for
only a few hours and then insert their mouthparts and begin to
feed. The remainder of the immature development is sessile.
Whiteflies feed exclusively on leaves, nearly always occurring on
the undersurface. They suck juices from the plants and also excrete
large quantities of honeydew in which sooty mold grows.
Feeding Damage and Symptoms
Whiteflies feed on more than 500 species of
host plants. Greenhouse-grown ornamentals such as poinsettia,
hibiscus, ivy, gerbera daisy, lantana, verbena, garden
chrysanthemum, salvia and mandevilla are especially susceptible to
whitefly damage. Whiteflies feed on plant phloem by injecting
enzymes and removing the sap, reducing the vigor of the plant.
Honeydew secretions from the whitefly promote the growth of sooty
mold which also significantly reduces plant quality. The most
obvious whitefly feeding damage symptoms are stem blanching,
chlorotic spots, leaf yellowing and shedding and, at high population
levels, plant death. In many crops the damage caused by Bemisia
tabaci is indirect. This species of whitefly is responsible for
transmitting many devastating viruses.
Detection and Sampling
Monitor whitefly population levels by trapping
winged adults on sticky cards and inspecting leaves for the presence
of feeding immatures. Strategically place yellow sticky cards
throughout the greenhouse, especially near doors and among new
plants to provide information about the presence and movement of
whiteflies. Detect whiteflies on plants by randomly selecting 10
plants per 1,000 square feet of greenhouse space and thoroughly
examining these plants on the underside of leaves, using a 10X hand
lens, for the presence of whitefly adults, nymphs and eggs.
Determination of biotypes is accomplished in the laboratory by using
sophisticated biochemical techniques. Therefore, growers will have
to send preserved whiteflies to one of the participating labs.
Currently, this pest is not rated as a pest with quarantine status
which means there are no legal requirements for these labs to report
their findings. Irrespective of which whitefly biotype you have it's
prudent to monitor for whiteflies and develop a Resistance
Management Program (RMP).
Chemical Control. Insecticides are the
primary method used to control whiteflies. Many compounds have been
used, but the systemic Marathon (imadacloprid) has been used most
frequently over the past few years. The newer chemically related
compounds Celero (clothianidin), Flagship (thiamethoxam), Safari
(dinotefuran), and TriStar (acetamiprid) are also effective.
Endeavor (pymetrozine), Aria (flonicamid), and the insect growth regulator (IGR) Distance
(pyriproxyfen) are new chemical classes that have activity as well.
There are several other effective IGRs: Azatin/Ornazin/AzaDirect (azadirachtin),
Enstar II (kinoprene), Pedestal (novaluron), and Talus
(buprofezin). The newest material to be registered for whitefly
control is Judo (spiromesifen). Tank mixes of orthene (acephate)
with a pyrethroid are synergistic, providing better control than
either alone. A few other general insecticides, aerosols and soaps
or oils can also be used. The newly hatched crawlers and the adults
are most susceptible to chemicals, but the waxy covering on the
larger immatures makes them more difficult to cover thoroughly with
spray material. Resistance is a PROBLEM and every effort should be made to rotate chemicals each time an
application is made don’t rely on any one product or chemical class
for whitefly control.
Exclude whiteflies from the greenhouse. Whiteflies are very small. Screens with a hole size of <0.19mm are
required to exclude adult whiteflies.
Be proactive, find them first. Scout
greenhouses by using sticky cards, leaf inspections or random
sampling techniques. Use this information as a basis for decisions
for chemical applications. Start any control practice early, when
the first whiteflies are detected. Control is difficult once
populations have increased to high levels.
Biological Control. Several biological agents are
available including predators (i.e. Orius, Delphastus, lacewing larvae, etc.), parasitoids (i.e. Eretmocerus, Encarsia, etc.) or pathogens (i.e. Beauveria bassiana, etc.).
Check with suppliers on compatibility with chemicals and
environmental requirements such as temperature, humidity, and
daylength. In Florida, Bemisia tabaci is effectively managed
on ornamentals and vegetables grown in greenhouses with Encaria
transvena. Other potential management tools that you probably
are not currently using. One area where nothing is currently being
done to manage pests is during transit or shipping of plants. Drs.
Lindquist, Oetting, and Osborne obtained significant whitefly
reduction by treating whitefly infested cuttings and plants with
insect pathogens just prior to boxing and shipping. A large grower
could easily produce their own insect pathogens that would be used
throughout the growing season in conjunction with all of the other
pesticides being used. A couple of the largest growers in Florida
are currently doing this. With fungi, it is not a typical case of
using either chemical or biological control. YOU CAN USE BOTH
WHAT CAN YOU DO?
First of all, don't panic! Growers that have the
Q-biotype in other parts of the world are still producing crops.
Go Back To The Basics
And Fine Tune Your Whitefly IPM Program!
Scout- Determine the extent of any whitefly problems. Make
sure everyone’s training is up to date and that employees are
sensitized to the fact that not all whiteflies are the same. If any
populations exist and the numbers or even their presence seems the
least bit unusual FIND OUT WHAT YOU HAVE. Studies have shown that in
a population that has both Q and B biotypes, increasing pesticide
applications will only increase the proportion of the population
that are the Q biotype.
Prevention- Don’t let new whiteflies into your operation.
You may not be able to prevent movement into your nursery from
outside sources but reduce your risk by inspecting new plant
material in a secure place so that whiteflies don’t escape.
Quarantine all new plant material introduced into your nursery.
Sanitation- Remove sources of infestation that might carry
over populations from one season to the next.
Cultural- Grow plants so as to facilitate good pesticide
coverage. If possible, try to have a crop free period so as to break
any cycling within your nursery.
Physical- Screening, weeding…
- a numbers game?
greater the number of whiteflies present when an application is made the greater
the chance that at least one individual might posses the ability to
survive the treatment.
The more frequently a given pesticide or mode of action is used
the greater the potential for developing a problem. Along those
same lines, the longer the residual activity the greater the
If no virus is involved in the system, then the ultimate goal is
not zero whiteflies throughout the production cycle but zero
whiteflies on the plant material leaving the facility. If this
statement can be agreed to, then we have a much better chance
managing resistance in whiteflies.
Older recommendations stated that “Insecticides should be applied
a minimum of two times at a five to seven day interval to
allow for egg hatch between applications so that both adults, nymphs
and individuals that hatch from eggs are killed. This is not
appropriate for many of the new pesticides that have residual
activity of one week or greater. If the insecticide is properly
applied and is not providing control, change to another material
with a different mode of action because whitefly populations have
the propensity to develop resistance. This is why scouting weekly
and especially after a pesticide application is critical.
includes several examples of insecticides listed according to their
chemical classification. Growers must learn from experience which
chemicals, when correctly applied, fail to give satisfactory
control, and to then try other materials in a different
a severe pest problem occurs on plants in the retail shop because a
few eggs, nymphs or adults survived even the best and most
conscientiously followed control program during production. It is
imperative, therefore, that your most effective pesticide be applied
to major whitefly host plants as close to the date of shipment as
There are a number of ways to deal with this
issue but the bottom line is; the fewer applications one makes of
materials from a given class, the smaller the potential for
resistance developing. To that end, what can be done? First
off, I recommend you develop a list of all the pesticides that are
legal to use for whitefly control on the crop you are growing.
Next, I suggest that each be evaluated under your particular
situation for phytotoxicity. When you are finished you will
have a list, hopefully not too short, from which you can develop a
management program. The next problem is to review the labels to find
restrictions/limitations on how often a material can be applied to a
given crop. The plan you put together should be based on all
of these points and the fact that growers will have to apply
materials to manage other pests. Scouting is essential to the
success of any pest management program.
From a resistance management perspective it
would seem prudent to treat with those materials highlighted
with yellow when the whitefly pressure and numbers are the
greatest. Once the population have been reduced then treatment
with those materials highlighted with green could be used.
The theory behind this is simple: DON'T USE YOUR BEST MATERIALS
AGAINST LARGE POPULATIONS BECAUSE THE LARGER THE POPULATION THE
GREATER THE CHANCE OF TREATING A RESISTANT WHITEFLY.
The Mode of Action information was obtained
Resistance Action Committee Mode of Action Classification
Products Chemical Class Chart
Class Chart Vol, XIII)
- Not all Q biotypes are going
to respond the same to insecticides. The strain detected by
Dennehy was shown to be highly resistant to a number of
newer insecticides but this does not mean that all future Q
biotypes detected in the US will be comparably resistant.
- The Q biotype detected by
Dennehy has reduced susceptibility to neonicotinoid
insecticides, including imidacloprid, thiamethoxam, and
acetamiprid. However, this does not necessarily mean that
these chemicals will fail to control the Q biotype,
especially under the conditions of treating potted plants.
- Based on tests of Q biotypes
conducted prior to the detection of the Q biotype in the US, it has been
concluded the neonicotinoid insecticide dinotefuran is
unaffected by the resistance of the Q biotype to
imidacloprid and other neonicotinoids. However, this result
has not yet been confirmed with the Q strain found in AZ.
- When Q biotypes are found in
the US and
“eliminated” with dinotefuran, or any other effective
insecticide, this in no way insures that the Q has been
eradicated at that location. There are few examples of
eradication of polyphagous, parthenogenetic homopteran