White flies are tiny, sap-sucking insects that are frequently abundant in vegetable and ornamental plantings. They excrete sticky honeydew and cause yellowing or death of leaves. The ability of the whitefly to carry and spread disease is the widest impact they have had on global food production. In the tropics and subtropics, whiteflies have become one of the most serious crop protection problems. Economic losses are estimated in the hundreds of millions of dollars.
Soapy water : If you want to use something safer than pesticides, soapy water will work. I use it sometimes when I need to spot treat small infestations.
- The problem with soapy water is I don't think it will kill all stages of white fly, only the adult stage. That means you will need to treat the plant about every three or four days for a couple weeks to kill the two or three generations you might have on your plant.
Neem oil : You can use Neem oil. Be sure to spray the soil, that's where they lay their eggs. Everytime I go to the nursery with a problem: pest, fungus, mold, etc. the answer is always Neem oil. I now start with this first. It almost makes the leaves shiny and beautiful.
Earthworm Castings : Earthworm poop. Yep, simple ol' earthworm poop aka Earthworm Castings! :) A farmer even told me this! What to do, get a huge bag of the earthworm castings and put cupfuls around your Hibiscus plants. Turn the soil over a bit around where you put the castings. Water away as usual. That's it! Somehow, the plant absorbs the 'stuff' and the nasty ol' White Flies don't like the way the Hibiscus tastes (I guess) anymore and won't lay eggs on it. Isn't that the craziest thing you've ever heard of?
I mentioned this to an agricultural scientist that said yep, I was correct, that Earthworm castings is one of the best things to use as a systemic in helping to keep White Flies away. :)
Isotox : Not organic, and it smells nasty for a couple days, but it works and will last longer than any of the organic methods. you do have to keep repeating treatments. Isotox is only for outdoor use.
Motor Oil : Paint strips of board yellow then paint on some motor oil. Guess it attracts the white fly there where a timely death follows.
Yellow Sticky Traps : Other than that, yellow sticky traps (kind of the same as the motor oil thing, but less of a hassle) help to lower the number of adults flies, so when you get rid of the larvae and eggs you don't have to worry about as many being laid.