As the days get longer, our indoor plants come back to life… and so do whiteflies. We often bring these insects into our homes in the fall on plants and cuttings we brought indoors or on our clothes when we work in the garden. However, they usually remain fairly inconspicuous through the fall and early winter, as they enter into diapause (dormancy) under the influence of short days. Now that the days are getting longer, however, they wake up and start to proliferate.
Whiteflies pierce the bottom of leaves of indoor plants (they are especially fond of herbs, hibiscus, poinsettias, fuchsias and pelargoniums), lapping up the sap that flows from the holes they provoke, and causing the plants to become yellowish and weak.
Although whiteflies are tiny, they are still readily visible, because they have the curious habit of flitting around the infested plant when disturbed, then quickly landing on the same plant or a neighboring plant. In fact, they look a lot like flying dandruff! You can’t really miss them when you’re watering your plants.
Whiteflies do have one fatal flaw you can used to control them: they are attracted to the color yellow. In nature, yellow indicates a weakened plant, one that is not likely to defend itself against attack, and thus a haven for whiteflies. In your home, you can take advantage of that by placing yellow sticky traps near susceptible plants. You can easily find such traps in garden centrers… or you can make your own from a piece of yellow cardboard or any object painted yellow by covering it in a sticky product such as motor oil, Tanglefoot sticky coating (sold in garden centers) or Vaseline.
The yellow color of the trap will attract adults who then land on it and remain prisoner. Do note that these traps will not touch whitefly young (called nymphs), as they remain fixed on the host leaf, but they too will stick to the trap as they reach adulthood and begin to fly.
When the traps are covered with adults, change them or (in the case of homemade traps) clean them and apply a new coat of sticky product.