Answer: The pest spray you are using is the right one, it's just that whiteflies are tenacious because they reproduce rapidly in warm temperatures. Outdoors, cold will eventually kill them off but indoor plants can be infested all year around. A strong blast of water from the hose often works, but you have to keep repeating the treatment. I have the best results when I spray early in the morning before the sun heats up. The pests will still be on the plants and the spray will kill any it touches. You might also try making traps. 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. I'm afraid you'll just have to keep after the problem on a regular basis until you get them under control. Good luck with your project!
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