How are we doing?
Find Us on Facebook Follow Us on Twitter
Follow us on Pinterst Visit the ATTRA Youtube Channel

What Is Sustainable Agriculture?

Master Publication List

Education

Energy Alternatives

Beginning Farmer

Field Crops

Horticultural Crops

Livestock & Pasture

Local Food Systems

Marketing, Business & Risk Management

Organic Farming

Pest Management

Soils & Compost

Water Management

Other Resources

Home Page


Contribute to NCAT



Newsletter icon Newsletters

Newsletter sign up button

· Privacy Policy
· Newsletter Archives




RSS Icon XML Feeds

RSS 2.0: Events, Breaking News, Funding Opportunties
Atom: Events, Breaking News, Funding Opportunties


NCAT strives to make our information available to everyone who needs it. If you are a limited-access or low-income farmer and find that one of our publications is just not in your budget, please call 800-346-9140.
Default Font Size Increase Font Size Increase Font Size
Home > Master Publication List > Greenhouse IPM: Sustainable Whitefly Control

Greenhouse IPM: Sustainable Whitefly Control

Pest Management Technical Note


Lance Greer
NCAT Agriculture Specialist
© NCAT 2000
IP168


Abstract

Whitefly
Whitefly.
www.extension.umn.edu/
yardandgarden

This publication focuses on integrated pest management for greenhouse whitefly on both vegetable and ornamental crops. It is designed to complement the ATTRA publication Integrated Pest Management for Greenhouse Crops, which discusses techniques for good greenhouse supervision. Monitoring of whiteflies, biological controls, biopesticides, and insect growth regulators are discussed below. The appendices include information on the newest biopesticides and biological control organisms.

Table of Contents

Introduction

Whiteflies began showing resistance to synthetic insecticides early on, and by the 1980s they were a very serious greenhouse pest. Not only do they feed on plants, but they also produce honeydew, which detracts from the plants' appearance and attracts other insects and sooty mold. Whiteflies can also transmit plant viruses. The mere presence of whiteflies in a greenhouse will stop customers from buying your product.

Several species of whiteflies attack greenhouse plants, and they typically have a wide host range and resist insecticides. Greenhouse tomatoes and poinsettias are especially plagued by whiteflies. The most common whiteflies on greenhouse crops are the greenhouse whitefly (Trialeurodes vaporariorum), sweetpotato whitefly (Bemisia tabaci) and the silverleaf whitefly (Bemisia argentifolii).

The various whitefly species and biotypes look very much alike, but they have subtle physiological differences. These differences can cause them to respond differently to control strategies. Because control measures must be selected according to the type of whitefly present, accurate identification is critical to successful control. The Cooperative Extension Service is an excellent resource for assistance with pest identification. There are also several Web sites that provide pictures of the various whiteflies. See the Web Sites section for more information.

Back to top

Crop Scouting and Trapping

Plants should be visually inspected for signs of a whitefly infestation—e.g., off-color or stunted plants. A hand lens is useful for systematically inspecting a number of individual plants for the presence of eggs, nymphs or adults. Both the upper and lower leaf surfaces should be inspected. It is important to check the greenhouse in the same pattern on each scouting trip. Locations where whiteflies are found should be flagged so that population development and control efforts can be evaluated. Scouting frequency should be increased during warm weather as whitefly populations multiply faster then.

Trapping with yellow sticky cards, both inside and outside the greenhouse, is essential for a successful whitefly management program. The cards are used to detect and monitor population levels. As a general rule, 1 to 4 cards spaced evenly throughout 1000 square feet of greenhouse are sufficient. (1) A generally acceptable threshold for whiteflies is 0.5 per card per day when the crop is young, and 2 per card per day as the crop reaches maturity. (2) Traps should be hung level with the tops of the plants since whiteflies are most attracted to young foliage. Doors, vents and other openings where whiteflies can enter the greenhouse are other good sites to hang yellow sticky cards.

Researchers in California have successfully used silver-painted pot spaces and silver polyethylene mulch to control whiteflies on greenhouse poinsettias. (3) The reflective materials were used in conjunction with yellow sticky cards or  tape and resulted in significantly enhanced trapping of whiteflies, relative to controls with sticky traps only.

Greenhouse plastics themselves may have significant influence on the initial attraction of insects into greenhouses. A study from the late 1990s showed that silverleaf whiteflies preferred to enter greenhouses covered with film that transmitted higher levels of ultraviolet light. (4)

Back to top

Biological Control

Several types of beneficial organisms are available for biological control of whiteflies. The parasitic wasp Encarsia formosa preys on immature whiteflies and is commonly used for greenhouse whitefly. Encarsia wasps kill whitefly nymphs in one of two ways: they either lay an egg inside the nymph, providing food for their young, or they kill the nymph right away and feed on the fluids inside of it. (2) Greenhouse whitefly pupae that have been parasitized by Encarsia formosa turn black; silverleaf whitefly pupae turn amber-brown. (2) The cost of E. formosa is comparable to foliar pesticides. (2)

Sweetpotato and silverleaf whiteflies are not well controlled by Encarsia formosa. Two other wasp parasites, Encarsia luteola and Eretmocerus californicus are commercially available for control of these species, but E. formosa remains the mainstay of most whitefly biological control programs due to the expense and intermittent availability of these other beneficials. (5) Researchers are also examining different strains of E. formosa to determine their effectiveness against sweetpotato and silverleaf whiteflies.

Mark Hoddle, University of California, Riverside, has done some recent research dealing with Eretmocerus eremicus. E. eremicus was effective for silverleaf whitefly control and is best used in combination with the insect growth regulators Precision™ or Applaud™. Enstar™ was not compatible with natural enemies he tested. Biological control should be used only at low whitefly levels (less than one nymph per 10 cuttings) and must be regularly evaluated. (6)

Mark has also compared the effectiveness of Encarsia formosa and Eretmocerus californicus on silverleaf whitefly. In a 1996 study, both parasitoids controlled whiteflies at a 99% control rate. However, fewer numbers of E. californicus had to be released, which would result in cost savings for growers. Another benefit: Fewer parasitoids meant more food for each, so the reproduction rate was much higher. (7)

Delphastus pusillus, sometimes called the whitefly destroyer, is a very small, black ladybird beetle that attacks all stages of whiteflies, but prefers eggs and nymphs. The females lay their eggs within clusters of whitefly eggs. Adults can consume 160 eggs or 12 large nymphs every day. A larva consumes 1000 whitefly eggs during its development. These beetles perform best at temperatures between 65 and 90°F, with relative humidity above 70%. These predators can be used in combination with Encarsia species. (8)

See Appendix 1 for a complete listing of biological controls for whiteflies.

Back to top

Biorational Pesticides

Some microorganisms also control whiteflies. For instance, the fungus Beauveria bassiana (trade names Naturalis-O™ and BotaniGard™), is effective against eggs, immature and adult whiteflies. Thorough coverage of leaf undersides and correct timing of applications result in best control.

Another fungus, Paecilomyces fumosoroseus (trade name PFR-97™), is now commercially available. It controls whiteflies, aphids, and spider mites. Both B. bassiana and P. fumosoroseus need high humidity for best results.

Several least-toxic, or biorational, pesticides have been evaluated for their effectiveness against the different whitefly species. These include neem-based formulations (Neemazad™ and Azatin™ are two registered products), insecticidal soap (M-Pede™), and horticultural oil. Enhanced whitefly control is achieved with thorough spray coverage. Wider plant spacing and removal of dead lower leaves improve pesticide coverage and pest control.

A 1995 study conducted in Florida compared the effectiveness of Sunspray Ultra-Fine Spray Oil™, M-Pede insecticidal soap, a sucrose ester extract surfactant derived from tobacco, and Garlic Barrier™, for killing and repelling silverleaf whiteflies (Bemisia argentifolii) on tomatoes. Sunspray provided the best control, followed by M-Pede and the tobacco surfactant. The Garlic Barrier did not provide any control. (9)

Researchers at Ohio State University showed that mortality rates of silverleaf whitefly were higher when BotaniGard was used together with Adept™ (an insect growth regulator), insecticidal soaps, horticultural oil, Fulex SO-2000, glycerol and a yeast extract. (10) In most cases, the rate of infection and kill was faster than with BotaniGard alone. This is important because it would allow more biopesticides and biorationals to be used retroactively. When several substances are used together, they are applied at lower-than-recommended rates (one-tenth to one-half were used in this study). The researchers are trying to "develop management guidelines on spray-tank mixes that would enhance fungal efficacy." (10)

See Appendix 2 for a complete listing of biopesticides and biorational pesticides available for whitefly management.

Back to top

Insect Growth Regulators

Insect growth regulators (IGRs) are another least-toxic pesticide control option. IGRs typically kill insects by disrupting their development. They have a complex mode of action that precludes insects from rapidly developing resistance. IGRs can work in one of several ways: 1) they can mimic juvenile hormones, so that insects never enter the reproductive stage of development; 2) they can interfere with the production of chitin, which makes up the shell of most insects; or 3) they can interfere with the molting process.

Table 1. Selected Insect Growth Regulators
Brand Name Supplier
Adept, Dimlin, Azatin Uniroyal Chemicals, Hydro-Gardens, Olympic Horticultural Products
Citation, Precision Novartis
Distance Valent
Enstar II Wellmark Int'l
Neemazad, Neemix Thermo Trilogy
Preclude, Pyrigro Whitmire Micro-Gen

IGRs usually work through ingestion, so good spray coverage is essential. They generally don't affect non-target species-such as humans, birds, fish or other vertebrates. For most IGRs there are minimal re-entry restrictions. IGRs typically take several days to have an effect on pest populations. Because IGRs do not affect mature insects, adult beneficials released into the greenhouse after an IGR application are not likely to be affected. Use of IGRs is generally prohibited by organic certification organizations because the products are synthetic.

IGRs can sometimes be used in conjunction with biological control efforts and may provide growers with a "safety net" should beneficials fail to keep the pests below economically damaging levels. The table above lists some well-known insect growth regulators.
(See the Suppliers section for suppliers' contact information.)

Back to top

Controlled Atmosphere

Changing the composition of the atmosphere in the greenhouse by either reducing oxygen or increasing carbon dioxide appears to provide some control of greenhouse whiteflies, especially adults. Reduced-oxygen experiments by Dr. Susan Han at the University of Massachusetts resulted in 100% adult mortality after less than two hours of exposure, though eight-hour treatments were needed to control most (about 80%) of the eggs and pupae. (11)

Horticulturists at North Carolina State University reported that whitefly population levels were lower in greenhouses where carbon dioxide enrichment occurred daily for about eight hours. The likely reason for the population reductions is that plants grown in atmospheres with high carbon dioxide levels tend to have higher concentrations of carbohydrates in the plant tissue relative to nitrogen, resulting in a nitrogen-dilute diet for the whiteflies. Lower dietary nitrogen would slow the growth and reproduction of the pests, without adversely affecting crop yields or quality. (12)

Back to top

References

  1. McHugh, Jennifer. 1991. Monitoring—the first line of defense. Greenhouse Grower. February. p. 66.

  2. Gill, Stanton. 2000. Pest control: whitefly control for cut flower growers.
    The Cut Flower Quarterly. Vol. 12, No. 1. p. 26-30.

  3. Price, Robert P. Jr. 1999. Reflective mulches and yellow sticky tape control whiteflies in greenhouse poinsettia (Euphorbia pulcherrima). As reported in Williams, Greg and Pat. From the 1999 ASHS conference. HortIdeas. August. p. 85.

  4. Costa, H.S. and K.L. Robb. 1999. Effects of ultraviolet-absorbing greenhouse plastic films on flight behavior of Bemisia argentifolii (Homoptera: Aleyrodidae) and Frankliniella occidentalis (Thysanoptera: Thripidae). Journal of Economic Entomology.
    June. p. 557-562.

  5. Anon. 1995. Biological pest control. Greenhouse Product News. July. p. 17.

  6. Daughtrey, Margery and Christine Casey. 1998. Highlights from SAF's pest conference. Grower Talks. April. p. 44, 46.

  7. Grossman, Joel. 1996. Conference notes. The IPM Practitioner. March. p. 14.

  8. Cloyd, Raymond A. 1999. Know your friends: Delphastus pusillus: whitefly predator. Midwest Biological Control News. October. p. 3.

  9. Williams, Greg and Pat. 1995. Oil, soap, surfactant, and garlic vs. whiteflies on tomatoes. HortIdeas. May. p. 55-56.

  10. Brownbridge, Michael, Margaret Skinner, and Bruce L. Parker. 2000. Enhancing the activity of insect-killing fungi for floral IPM. Ohio Florists' Association Bulletin.
    January. p.14-16.

  11. Anon. 1995. Controlled atmosphere to manage whitefly. The Cut Flower Quarterly. July. p. 14-16.

  12. Tripp, Kim and Mary Peet. 1993. New use for CO2: Slowing whiteflies. American Vegetable Grower. November. p. 43-44

Back to top

Web Sites

USDA's Whitefly Knowledgebase

Information on silverleaf whitefly from the University of Florida

 

Back to top

Suppliers

A-1 Unique Insect Control
5504 Sperry Drive
Citrus Heights, CA 95621
916-961-7945
916-967-7082 FAX
ladybugs@a-1unique.com
Mycogen Crop Protection
5501 Oberlin Dr.
San Diego, CA 92121
800-745-7476
619-453-9089 FAX
soares@mycogen.com
ARBICO Inc.
P.O. Box 4247 CRB
Tucson, AZ 85738
800-SOS-BUGS
520-825-2038 FAX
arbico@aol.com
Mycotech Corp.
P.O. Box 4109
Butte, MT 59702-4109
800-383-4310
406-782-9912 FAX
mycotech@montana.com
Beneficial Insectary
14751 Oak Run Rd.
Oak Run, CA 96069
800-477-3715
530-472-3523 FAX
bi@insectary.com
Natural Pest Controls
8864 Little Creek Dr.
Orangeville, CA 95662
916-726-0855
916-726-0855 FAX
natpestc@cwnet.com
BioLogic Co.
P.O. Box 177
Willow Hill, PA 17271
pyealber@epix.net
717-349-2789/292
Nature's Control
P.O. Box 35
Medford, OR 97501
800-698-6250
541-899-9121 FAX
bugsnc@teleport.com
Caltec Agri-Marketing Services
P.O. Box 576155
Modesto, CA 95357
209-575-1295
209-575-0366 FAX
Novartis Crop Protection, Inc.
P.O. Box 18300
Greensboro, NC 27419-8300
800-395-8873
See www.zeneca.com/en/index.aspx
Florikan ESA Corp.
1523 Edger Place
Sarasota, FL 34240
800-322-8666
941-377-3633 FAX
Plantadvice@Florikan.com
Olympic Horticultural Products
P.O. Box 1885
Bradenton, FL 34206-1885
800-659-6745
The Green Spot, Ltd.
93 Priest Rd.
Nottingham, NH 03290-6204
603-942-8925
603-942-8932
603-942-5027 (voice mail)
GrnSpt@internetMCI.com
Plant Health Care
440 William Pitt Way
Pittsburg, PA 15238
800-421-9051
Harmony Farm Supply
3244 Hwy. 116 No. F
Sebastopol, CA 95472
707-823-9125
707-823-1734 FAX
kate@harmonyfarm.com
Rincon-Vitova Insectaries, Inc.
P.O. Box 1555
Ventura, CA 93002
800-248-2847
805-643-6267 FAX
bugnet@west.net
Hot Pepper Wax, Inc.
305 Third St.
Greenville, PA 16125
888-667-3785
724-646-2302 FAX
lindag@hotpepperwax.com
SePRO Corp.
11550 N. Meridian St., Suite 180
Carmel, IN 46032-4562
800-419-7779
317-580-8290 FAX
rogers@sepro.com
Hydro-Gardens, Inc.
P.O. Box 25845
Colorado Springs, CO 80932
719-495-2266
719-531-0506 FAX
Soil Technologies Corp.
2103 185th St.
Fairfield, IA 52556
800-221-7645
515-472-6189 FAX
info@soiltechcorp.com
International Technology Services Inc.
P.O. Box 19227
Boulder, CO 80308-2227
303-473-9141
303-473-9143 FAX
intertechserv@worldnet.att.net
Stoller Enterprises, Inc.
8582 Katy Freeway, Suite 200
Houston, TX 77024
800-539-5283
713-461-4467 FAX
IPM Laboratories
P.O. Box 300
Locke, NY 13092-0099
315-497-2063
315-497-3129 FAX
Wellmark International
1000 Tower Lane, Suite 245
Bensonville, IL 60106
800-842-3135
630-227-6065 FAX
M&R Durango, Inc.
P.O. Box 886
Bayfield, CO 81122
970-259-3521
970-259-3857 FAX
Whitmore Micro-Gen
3568 Tree Court Ind. Blvd.
St. Louis, MO 63122
800-777-8570
314-225-3739 FAX

Back to top

Appendix 1: Beneficial Organisms

Organism Supplier Pests Controlled Application/Comments
Chrysopa carnea (predator) Natural Pest Controls, Beneficial Insectary, Caltec, Arbico, A-1 Unique Insect Control, Praxis, Rincon-Vitova, Hydro-Gardens aphids, caterpillars, mealybugs, scales, spider mites, thrips, whiteflies 1 lacewing/5-30 aphids; 1000 eggs/200 sq. ft. Apply every 1-3 weeks as needed. May arrive as eggs, immatures, or adults.
Chrysoperla rufilabris (predator) Arbico, Beneficial Insectary, IPM Labs., A-1 Unique Insect Control, Nature's Control, Praxis, Rincon-Vitova see above  
Chrysoperla spp. (predator) M&R Durango, Florikan, Green Spot see above  
Coleomegilla imaculata
(pink ladybird beetle)
Arbico aphids, caterpillars,mites, scales, thrips,
whiteflies
1/sq. ft.; shipped as larvae and eggs.
Deraeocoris brevis (predator) Green Spot aphids, whiteflies, thrips  
Delphastus pusillus
(predatory beetle)
Arbico, IPM Laboratories, Nature's Control, Harmony Farm Supply, Hydro-Gardens, Rincon-Vitova, Praxis, Green Spot greenhouse whitefly, sweetpotato whitefly 2000/3000 sq. ft.; temperature should be 60-85°F. Will feed on spider mites if no whiteflies are available. Should be used along with Encarsia formosa and traps.
Encarsia formosa (parasitic wasp) Arbico, Nature's Control, IPM Laboratories Intl. Technology)Services, Florikan, Harmony Farm Supply, Hydro-Gardens, Natural Pest Controls, A-1 Unique Insect Control, Praxis, Rincon-Vitova, Green Spot greenhouse whitefly, sweetpotato whitefly, silverleaf whitefly Release 1/sq. ft. weekly for 3 weeks when pest numbers are low. Release 2-4/sq. ft. when pest numbers are high. Apply when pests are first observed. Should be used in conjunction with traps. May be used along with other beneficials. E. formosa is very susceptible to chemicals. Temps. should be at least 64°F. Re-apply every two weeks.
Encarsia luteola or
E. deserti
Hydro-Gardens whiteflies  
Eretmocerus californicus or E. eremicus (parasitic wasp) Beneficial Insectary, Hydro- Gardens, IPM Labs., Arbico, Praxis, Green Spot greenhouse whitefly, silverleaf whitefly, sweetpotato whitefly Capable of handling hot, dry temperatures. Introduce when whiteflies are first observed. May be used in combination with other beneficials such as green lacewings. Eretmocerus is more tolerant of pesticides than Encarsia formosa.
Harmonia axyridis (Asian lady beetle) Green Spot scale, whiteflies, mealybugs, aphids Temps. should be 70-85°F; humidity around 70%.
Hippodamia convergens (lady beetle) (predator) A-1 Unique Insect Control, Arbico, Caltec, IPM Laboratories, Natural Pest Controls, Nature's Control, Harmony Farm Supply, Hydro-Gardens, Praxis, Green Spot aphids, mites, whiteflies Release at dusk near an immediate food source. Spray plants with water prior to release.

Back to top

Appendix 2: Biorational Pesticides

Azadirachtin—extract of neem seed; IGR that works through contact or ingestion
Brand Name Supplier Pests Controlled REI Application/Comments
Azatin Green Spot Aphids, caterpillars, fungus gnats, leafhoppers, leafminers, Western flower thrips, whiteflies, psyllids 4 hours Apply when pests first appear.
Neemazad Thermo Trilogy Aphids, caterpillars, thrips, greenhouse whitefly, leafminers, sweet potato whitefly, psyllids, leafhoppers 12 hours Cannot be applied through irrigation. Low rate can be used as a preventive.
Beauveria bassiana—fungus that works through contact; exposure to non-target insects should be avoided
Naturalis-O SePro aphids, caterpillars, mites, psyllids, thrips, whiteflies 4 hours Apply when insects first appear and repeat every 7-10 days. Need good spray coverage. Not compatible with other fungicides.
BotaniGard Mycotech giant whitefly, green peach aphid, black vine weevil, others aphids and whiteflies, thrips, leafhoppers, psyllids, white grubs 12 hours See above.
Garlic extracts
Garlic Gard Soil Technologies repels many insects   Use late in the day. Can be mixed with fish oil or horticultural oil.
Garlic Barrier Green Spot repels many insects 4 hours Do not use in combination with bumblebees or honeybees.
Horticultural oil—includes dormant and summer superior oils
All Seasons Green Spot aphids, mealybugs, scales, thrips, whiteflies, spider mites 4 hours Use on sunny days to promote rapid drying and decrease chance of phytotoxicity. Not compatible with beneficials
Hot pepper wax—contains capsaicin, parrafin, and mineral oil
Hot Pepper Wax Green Spot aphids, loopers, beet armyworms, mites, whiteflies, thrips, mealybugs, etc. 4 hours Also contains herbal essential oils. Not compatible with beneficials.
Hot Pepper Wax Hot Pepper Wax, Inc. see above 0 hours  
Insecticidal soap—contains potassium salts of fatty acids
M-Pede Mycogen aphids, mealybugs, scales, thrips, whiteflies, spider mites 12 hours Phyotoxicity is often a concern, epseically after repeated applications.
Safer Green Spot see above 4 hours See above.
Insecticidal soap Olympic see above    
Neem oil— multi-purpose organic insecticide/fungicide/miticide; kills eggs, larval and adult stages of insects
Trilogy 90EC Thermo Trilogy greenhouse whitefly, silverleaf whitefly, sweetpotato whitefly, thrips, whiteflies, leafminers, aphids, mites, psyllids, San Jose scale, scale, spider mites, downy mildew, powdery mildew, Alternaria, Botrytis, etc. 4 hours Apply at first signs of damage. Repeat every 7-10 days as needed.
Triact 90EC Thermo Trilogy see above 4 hours For ornamental crops only.
Paecilomyces fumosoroseus—fungus
PFR-97 Olympic whiteflies, aphids, spider mites, Western flower thrips 4 hours  
Soybean oil
Golden Natur'l Spray Oil Stoller aphids, fungus gnats, lace bugs, leafminers, scales, mealybugs, spider mites, whiteflies 12 hours  

 


Greenhouse IPM: Sustainable Whitefly Control
By Lance Greer
NCAT Agriculture Specialist
Tiffany Nitschke, HTML Production
IP168
Slot 64

 

Back to top

This page was last updated on: April 26, 2012