Adult whiteflies look like tiny moths with white, waxy wings. The nymph stage resembles small white waxy scales. Whiteflies damage plants by sucking the juices and secreting sticky residue that grows mold. The scale stage is hard to kill, but adults are more easily controlled. Traps can prevent the adults from laying eggs. Homemade sprays may be used to control whiteflies in greenhouses and on indoor potted plants. For ornamental plants outside homemade sprays provide better control since weather can ruin traps.
Indoor Potted Plant Insecticide
Remove adult white flies first with a small hand vacuum or the brush attachment on a regular vacuum. Smaller potted plants can be held under the shower to remove adults. Be sure to cover the potting soil so it doesn't come out of the pot.
Make a 70 percent isopropyl alcohol (rubbing alcohol) spray solution. Mix 2 cups of alcohol in 1 quart of water. Do not use more alcohol because it may burn houseplants with hairy or fleshy leaves.
Test the solution on a portion of each plant first as some plants are sensitive to alcohol. Fill a spray bottle and spray the solution on all parts of non-sensitive plants. Coat the stems and undersides of leaves.
Use a soap solution for sensitive plants. Grate 8 oz. (16 tbsp.) of Fels-Naptha or Ivory soap. Stir the soap into 2 1/4 gallons of water till it completely dissolves. Test for sensitivity by swabbing on the underside of a leaf.
Apply the soap solution to all parts of non-sensitive plants and let dry overnight. Wash plants the next day by holding the foliage under running water, or take large pots outside and hose them with a fine spray.
Outdoor Whitefly Insecticide
Mash enough garlic cloves to produce a cup of crushed garlic. Add 4 tsp. of mineral oil, mix well, and let it sit for one day.
Add 4 cups of water and 1 tbsp. of Safer's Soap. Mix everything well and let it sit for two hours, then strain the solution.
Use 1 tbsp. of solution for every 2 cups of water in your pump sprayer. Coat all parts of your plants including the undersides of leaves. Do not use a sprayer that has been used for herbicide or other insecticides.