Friday, April 3, 2015

Whitefly Control for Organic Gardeners

I collected this information for a neighbor this morning and thought it might interest others.
Organic Whitefly Control
  • Aluminum reflective mulch repels whiteflies by making it difficult for them to find host plants. This is a good way to protect tomatoes and peppers from diseases spread by whiteflies.
  • Use yellow sticky traps to monitor or collect whiteflies lurking among tomatoes, peppers, sweet potatoes or cabbage family crops. A half-and-half mixture of petroleum jelly and dishwashing detergent, spread over small boards painted bright yellow, is sticky enough to catch little whiteflies.
  • Blast whiteflies from leaf undersides with a strong jet of water. Then apply a weak solution of insecticidal soap, preferably late in the afternoon. Repeat after one week.
  • A small vacuum is the best way to remove whiteflies from plants because it will remove both nymphs and larvae. If you have chickens, allow them to peck through infested plant foliage before you compost it.
  • Never use chemical insecticides in attempt to control whiteflies. Many strains are pesticide-resistant, but their predators are not. You may accidentally kill many beneficial insects, and the whiteflies will bounce right back.
More Advice on Organic Whitefly Control
Gardens that host an abundance of beneficial insects make poor homes for whiteflies. In areas where whiteflies are common and your neighbors use a lot of pesticides, monitor populations with sticky traps and use a vacuum to keep small outbreaks under control.  In seasons following whitefly problems, avoid planting attractive annuals such as lantana, salvia and hibiscus.
More information on organic whitefly control is available from the University of CaliforniaMississippi State University and the University of Missouri.
Least-Toxic Chemical Controls
Whiteflies began showing resistance to synthetic insecticides many years ago, and have since become a major problem in some crops and greenhouses. To control an infestation use a suitable organic spray as soon as adults are noticed, make sure you spray underneath the leaves.
  • Insecticidal soap sprays such as Natrasoap are a good choice of control for the home gardener; spray every 2-3 days for 2 weeks.
  • Spray Eco-Oil or try making your own oil spray by mixing 1 tablespoon dishwashing liquid detergent with 1 cup of cooking oil; add 1 to 2.5 teaspoons of this solution to 1 cup of water, spray onto plants every 10 days.
  • Botanical insecticides such as Beat-A-Bug Insect Spray are useful. Research undertaken in NZ on neem's effectiveness for whitefly found that it had a major impact by preventing the 'nymph' stage from developing into an adult; the nymphs tend to disappear from the treated plants.
Whitefly Control
Yellow sticky traps are helpful for monitoring and suppressing adult populations. If found, use the Bug Blaster to hose off plants with a strong stream of water and reduce pest numbers. Natural predators of this pest include ladybugs and lacewing larvae, which feed on their eggs and the whitefly parasite which destroys nymphs and pupae. For best results, make releases when pest levels are low to medium. If populations are high, use a least-toxic, short-lived organic pesticide to establish control, then release predatory insects to maintain control. Insecticidal soap, neem oil and botanical insecticides can be used to spot treat heavily infested areas if population become intolerable.
Tip: Horticultural oils, which work by smothering insects, are very effective on all stages of this pest.
Note: Ants feed on the honeydew that sucking insects produce and will protect these pests from their natural enemies. An application of Tanglefoot Pest Barrier to the stalks of roses and other woody plants will help get rid of ants.
Preventative Measures
Use a seaweed spray to mist the leaves of your plants. Along with all the benefits plants derive from a seaweed spray it also seems to make the foliage undesirable for whiteflies to reproduce on. Spray garden plants in spring, houseplants at least a week before bringing inside and use in the greenhouse for seedlings and as needed. Try our Seaweed Powder.
Insecticidal soap: White flies are soft-bodied insects and can be successfully controlled and prevented with insect soap sprays. Our customers and we highly recommend our Insect Soap for whiteflies.
Repellant plants: African, French marigolds (Tagetes), Calendula, nasturtiums, and Peruvian cherry.
Shoofly plant traps whiteflies on it leaves making it a perfect choice to control and monitor the little devils in the greenhouse or home.
Direct Controls
Use a vacuum to carefully suck up as many whiteflies as you can. Insect or dustbuster units are ideal.
Here's a recipe for whiteflies to try:
  • Mix 1 tablespoon of insecticidal soap, 1 cup of 70% isopropyl alcohol and 1 quart of water. Proceed to spray at least 2 times 7 days apart. Spray heavily to the point of runoff. Do not breath the mist of this as the isopropyl alcohol is poisonous. When used with care it can be effective. Do test for alcohol sensitivity on plants as isopropyl alcohol will dissolve the natural coating on plants that have waxy leaves. Do not use on seedlings. Though not as strong and more expensive, vodka may be substituted for the isopropyl alcohol. 
Whiteflies cam be an indicator of phosphorous and magnesium  deficiencies. You can correct magnesium deficiencies by mixing 4 ounces of Epsom salts with 1 gallon of water. Use as a soil soak for infested plants. We won't say that this is a cure all but it can certainly benefit your plant especially tomatoes and peppers.