White flies took a liking to my watermelon vine. A quick spritz with the insecticidal soap in the evening and the next morning when I went back to the greenhouse, no more white flies! I also hung up a yellow fly cone and found quite a few on it as well.
White flies are attracted to the color yellow. The yellow fly cone and yellow flat sticky boards sold in garden centers are effective traps for white flies.
With these two items, you will have an organic arsenal against white flies!