Surrounding your plant with reflective material such as aluminum or silver polyethylene mulch that reflects light up onto the leaves of plants (also known as Aluminum Reflective Mulch), makes it difficult for whiteflies to find the plant. If you have a limited budget you can cover cardboard with aluminum foil.
Read more at Gardening Know How: Reflective Mulch Info: Is Reflective Mulch Effective In Gardens https://www.gardeningknowhow.com/garden-how-to/mulch/using-reflective-mulch-in-gardens.htm
How does it defer whiteflies? They are simply confused by the light. The use of this mulch is particularly good for protecting your vegetables from diseases that whiteflies can transmit.
A note from Gail: I’ve never tried this approach in either my garden or Aquaponic system. I’ve always simply knocked the whiteflies off the plants by backing the plant up with my hand then gently spraying the hose (shower mode) onto the leaves. If you repeat 2-3 times each week, the infestation should slowly disappear.