The Q&A Archives: Whiteflies Out Of Control Indoors

Question: We added a heated solarium on the side of our home about 1.5 yrs ago, and we left most of the original ground in the room to plan a rose tree, hybiscus and other plants. During winter when the room is closed up, I have a terrible time with whiteflies. I have to spray insecticide once a week or they multiply and spread from plant to plant, focusing on my hybiscus. Spraying kills them instantly, but they start coming back within days. How can I kill these bugs once and for all without having to continually spray? I also am having a small problem with spider mite, primarily on my rose bush, the white flies are the biggest problem. The room is very moist because of all the plants and it's enclosed and heated (both solar and gas heat). Any suggestions you have on how to get rid of these pests?

Answer: Whiteflies are tenacious because they reproduce rapidly in warm temperatures. Outdoors, cold will eventually kill them off but since you indoors that won't help. A strong blast of water from the hose often works, but that's impractical for you so try a soapy water spray, using a hand held spritzer. Spray underneath leaves where they hang out. Do this daily if you notice insects.

Use 1 teaspoon to 2 tablespoons of liquid detergent soap per gallon of water. Use regular, not concentrated soap. Don't use soaps with lemon, as the citric acid can burn plants. Start with the lower amount and work up as needed. Spray as often as needed. As with any spray you might wish to test it on a few leaves first before you treat all your plants. Spray early in the morning before the sun heats up.

Whiteflies are attracted to the color yellow. You can purchase or make yellow "sticky" traps from yellow cardboard smeared with petroleum jelly. They fly to it and get stuck.

Next on my list would be an insecticidal soap spray. The insecticidal soaps are made from plant-derived fatty acids and target soft-bodied insects. There is really no effective chemical spray for whiteflies but researchers are working on it. I'm afraid you'll just have to keep after the problem on a regular basis until you get them under control.

Spider mites are best controlled with a daily blast of water. (Mites like dusty plants.) The humidity from the extra water also helps the plant. If possible, spray early in the morning, before the sun gets too hot. If that doesn't work, try an insecticidal soap.
Good luck!

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