These small sucking insects have developed resistance to many synthetic pesticides making chemical control difficult. Here’s how to get rid of whitefly using proven, organic techniques.
Common on houseplants and in greenhouses, the whitefly (Trialeurodes vaporariorum) is a sap-sucking insect that is often found in thick crowds on the undersides of leaves. When infested plants are disturbed, great clouds of the winged adults fly into the air. Both nymphs and adults damage plants by sucking the juices from new growth causing stunted growth, leaf yellowing and reduced yields. Plants become weak and susceptible to disease. Like aphids, whiteflies secrete honeydew, so leaves maybe sticky or covered with a black sooty mold. They are also responsible for transmitting several plant viruses.
In southern and coastal states whiteflies are found year-round in outdoor gardens. In northern areas year-round infestations are possible only indoors. Host plants include more than 250 ornamental and vegetable plants. Citrus, squash, poinsettia, potato, cucumber, grape, tomato and hibiscus are commonly infested.
Adults (1/16 inch long) are moth-like insects with powdery white wings and short antenna. They are easily recognized and often found near the tops of plants or on stem ends. Wingless nymphs are flattened, oval and almost scale-like in appearance. After the first instar, or crawler stage, they settle down and attach themselves to the underside of leaves and begin feeding.
Life Cycle
Young nymphs overwinter on the leaves of host plants. In late spring adult females deposit 200-400 eggs in circular clusters on the undersides of upper leaves. The eggs hatch in 5-10 days and first instar nymphs, which resemble small mealybugs and are called crawlers, move a short distance from the egg before flattening themselves against the leaf to feed. The remaining nymphal stages (2nd, 3rd and 4th) do not move. A non-feeding pupal stage follows and within a week, young adults emerge to repeat the cycle. There are many generations per year. Whiteflies develop from egg to adult in approximately 25 days at room temperature. Adults may live for one to two months.
Note: All of the immature stages are easily overlooked. They are usually pale, almost translucent, and blend with the color of the leaf to which they are attached. Superficially they are similar to several scale insects.
Whitefly Insecticide Recipe
You can mix up a simple recipe for an insecticide spray for whiteflies right in your kitchen. First, make a base mixture with 1 tablespoon of regular dish soap (not one with added bleach or an antibacterial soap) and 1 cup of vegetable oil. Pour it into a bottle that can be sealed, and shake well to mix. Note: This recipe must be diluted before using it on your plants.
Diluting the Recipe
Now that you have your base, you can mix 1 1/2 teaspoons of it into a cup of water. Mix this in a spray bottle, and shake it well. Oil and water do not mix, so it needs to be shaken often as you are using it.
Using the Spray
Once your spray is properly diluted and mixed, you can spray your affected plants. Be sure to spray the undersides of leaves, since this is where the whiteflies tend to be. This mixture kills adult whiteflies and smothers the larvae and eggs as long as they are covered in the spray, so be sure to apply it liberally. Reapply as needed after rain or watering your plants for the best results. Be sure to spray plants early in the morning or late in the day when temperatures are cooler, as the heat may cause an adverse reaction in your plant.
Alternate Recipe
Another recipe, from The Old Farmer’s Almanac, recommends a mixture of five parts water, two parts rubbing alcohol and 1 tablespoon of dish soap. Mix well, and spray it on the leaves of affected plants. You might want to test this on one leaf first, in case the rubbing alcohol is damaging to the plant.
Source:
1. http://homeguides.sfgate.com/homemade-whitefly-insecticide-37740.html
2. https://www.planetnatural.com/pest-problem-solver/houseplant-pests/whitefly-control/
