What is the Most Effective Treatment for Whitefly Infestations on Plants?
AbstractWhiteflies are a group of closely related insect species whose larvae live on plants. Like aphids, they suck nutrients from the plant's circulatory system. What is the most effective method for fighting a whitefly infestation in your garden? This project has some ideas for you to try.
The objective of this project is to determine the most effective treatment for whitefly infestations on garden plants (e.g., Hibiscus, tomato, poinsettia, and others). Potential treatments for comparison include: soaps, oils, biopesticides, insect growth regulators, or insecticides. The different treatments are compared to each other and to a treatment of water alone.
Andrew Olson, Ph.D., Science Buddies
This project is based on:
- Joyce, A.M., 2003. "The Effectiveness of Commercial Products vs. Home Remedies on Whitefly," California State Science Fair Abstract [accessed October 16, 2006] http://www.usc.edu/CSSF/History/2003/Projects/J1418.pdf.
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Whiteflies (see pictures in Figure 1) are a group of related insect pests whose larvae, like aphids, get nutrients by sucking juices from plant leaves and stems. In addition to the primary damage they cause by depriving plants of vital nutrients, whiteflies can cause harm in other ways. They secrete relatively large quantities of honeydew, which encourages the growth of harmful fungus, and may also attract other harmful insects. Whiteflies can also transmit viruses which cause disease in plants.
Figure 1. Four different species of whitefly (clockwise from top left): bandedwinged whitefly, greenhouse whitefly, sweet potato whitefly, and silverleaf whitefly (Fasulo et al., 1995).
Whiteflies have predators, including some parasitic wasp species, and ladybugs. Using broad-spectrum insecticide treatments to try to control whiteflies can lead to killing off these predators, and to the development of insecticide resistance in the whiteflies that survive.
Biorational pesticides are more focused methods of chemical control that aim to manage the pest species with the minimum amount of disturbance to non-target species. Biorational pesticides for whitefly control include insecticidal soaps and oils, and insect growth regulators, which kill by delaying larval development.
In this project, you'll compare the effectiveness of different treatments for controlling whiteflies.
Terms and Concepts
To do this project, you should do research that enables you to understand the following terms and concepts:
- Greenhouse whitefly
- Bandedwinged whitefly
- Silverleaf whitefly
- Sweet potato whitefly
- How to identify them
- Most effective pest management strategies for each
- Integrated pest management (IPM)
- Biorational insecticides:
- Insecticidal soaps and oils
- Insect growth regulators
- What are some disadvantages to using insecticide treatments for insect pests in the garden?
- Fasulo, T.R., et al., 1995. "USDA Whitefly Knowledgebase," United States Department of Agriculture and Department of Entomology and Nematology, University of Florida [accessed October 16, 2006] http://entnemdept.ufl.edu/fasulo/whiteflies/wfly0002.htm.
- Wikipedia contributors, 2006. "Whitefly," Wikipedia, The Free Encyclopedia [accessed October 16, 2006] http://en.wikipedia.org/w/index.php?title=Whitefly&oldid=80716701.
- Greer, L., 2000. "Greenhouse IPM: Sustainable Whitefly Control," ATTRA Pest Management Technical Note [accessed October 16, 2006] https://attra.ncat.org/attra-pub/summaries/summary.php?pub=51.
- Cranshaw, W.S. and B. Baxendale, 1999. "Insect Control: Horticultural Oils," Colorado State University Cooperative Extension [accessed November 3, 2006] http://www.ext.colostate.edu/PUBS/INSECT/05569.html.
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Materials and Equipment
- Plant(s) with whitefly infestation:
- Many plants are susceptible, e.g., Hibiscus, tomato, poinsettia, and others;
- If the plant is large enough (e.g., hibiscus), you can try different treatments on different branches.
- You will need to research and select 3–5 different control methods to test. Some of these may be available at a local hardware store or plant store/nursery. Be sure to follow all safety labels for any product, including for necessary protective gear (see below). For example, you could test:
- Horticultural oil, available on Amazon.com.
- Insecticidal soap, available on Amazon.com. One brand name is M-Pede.
- Insect growth regulator, available on Amazon.com. See Greer, 2000 in the Bibliography in the Background for some specific examples.
- Biopesticides. Use ones that are based on insect-killing fungus, Beauveria bassiana or Paecilomyces fumosoroseus, such as the brand names Naturalis-O, BotaniGard, or PFR-97.
- Spray bottles for administering different treatments, available from Amazon.com
- Depending on the warning labels for the treatments you choose, you may need specific safety gear. The items below are just suggestions based on some common pesticide warning labels, but be sure to follow the specific warning labels for your products.
- Chemical splash goggles, available on Amazon.com
- Chemical-resistant gloves, available on Amazon.com
- A particulate respirator, available on Amazon.com. Note that respirators have different ratings, for example "P95" and "R95". If you do need a respirator, make sure to get the exact kind that is recommended on your pesticide's warning label.
- Long pants and a long-sleeve shirt
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- Do your background research to make sure that you are knowledgeable about the terms, concepts, and questions above.
- As you learned when doing your background research, accurate identification of the particular whitefly species is important, since there are differences in control strategies. Use the ID Key webpages from the Whitefly Knowldedgebase, or seek help from a local greenhouse expert or county agricultural extension agent.
- Based on your background research, select 3–5 different treatments for testing.
- Before any treatments, take photographs and perform counts to determine the level of whitefly infestation. Record the results in your lab notebook.
- Clearly mark the different garden areas (or different branches of the same plant) for each treatment.
- Prepare and apply the different treatments according to the manufacturer's instructions. Be sure to follow all safety instructions when spraying.
- Use a plain water spray as a negative control.
- Continue to perform whitefly counts and take photographs for each treatment area at regular intervals for two weeks. Record the results in your lab notebook.
- Make graphs of the whitefly counts vs. time for each of the treatment areas.
- Which treatment is most effective?
Communicating Your Results: Start Planning Your Display BoardCreate an award-winning display board with tips and design ideas from the experts at ArtSkills.
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- Ladybugs (both adults and larvae) are natural predators of whitefly eggs and larvae. Can introduction of ladybugs control a whitefly infestation?
- Compare the cost effectiveness of different treatments. Which one delivers the best results per dollar?
- For a more advanced (and longer-term) project you could compare integrated pest management techniques vs. a single treatment. To do this, you would need multiple areas with similar infestations for testing (e.g., multiple fields, greenhouses, or your garden plus those of one or two friends).
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