Another great question came to Ask Gardenerd this week:
“We have whiteflies on our hibiscus trees, and I was wondering if there is a pesticide-free way to get rid of them. The infestation is on one tree, and I don’t want it to spread to the other trees or anything else in our garden. We have dogs, and I don’t want to use malathion or diazinon. What would be safe to use?Thanks!”
In many cases, your hose is your best friend. If you have a hose nozzle set on my favorite setting: Kill (read: Jet or Full), you can blast those whiteflies from the underside of the leaves on a weekly basis or as needed. If you’re worried about them spreading, there are a couple other options:
Boost your soil – white flies usually show up when a plant is showing weakness. Give your plants a shot of fish or kelp emulsion weekly (diluted in a bucket of water) and see if that helps. I would do this in combination with a jet spray of water.
Horticultural Oil- you can foliar spray your tree with a harmless-to-humans-and-pets solution of a vegetable oil mixture. There are many available, including Neem Oil, a canola-based oil from Concern, and Garden’s Alive carries one called Oil-Away Supreme Insecticidal Spray. If you click on the link, go to page 5 of the listings and you’ll see it there.
These oils are mixed with water and sprayed during cool parts of the day so the plant doesn’t burn.
Sticky Traps – These are yellow cards that are coated with sticky substances. The whiteflies (and flea beetles and other small bugs) are attracted to them. They land and can’t leave, so they basically starve to death. These are usually used for houseplants, but you can use them outdoors as well. You might need a lot of them to make them effective. Garden’s Alive has them on page 2 at this link: Pot Stickers. Gardener’s Supply also carries a sticky trap:
Try those and see how it works for you. Either way your pets will be safe and your hibiscus will be much happier.
Thanks for writing in!