Hi

You can use a variety of methods.

Spray the plants with a solution of 'Farina' (potato starch). 1 tablespoon to a couple of pints of water and shaken vigorously. Spray this on the undersides of the leaves (where the flies hide) and leave overnight. This MUST be well rinsed off in the morning with clear water. If you don't rinse them the plants will not be able to transpire and you will cause more harm than good. Any sprayer used MUST also be rinsed straight away or the pipes and nozzle get clogged up.

As with any spraying carried out, a 'one off' attack will not cure the proble. The whitefly (or wwhatever pest) has different stages of their life cycle happening at the same time and the effects on one stage may not be detrimental to the other stages, When I had any whitefly I sprayed on a four day cycle until they had gone. Hatd work I know, but no more whitefly.

I use a chemical which is available here in the UK called "Provado Ultmate Bug Killer", this contains 'Imidacloprid' which may be available to you under a different name? This is systemic and the manufacturers claim that it works for up to 8 weeks. I use it more frequently than that and I haven't seen any aphids, thrips or whitefly this growing season.

Sticky traps can also be used but these are less effective in the open garden than when used in a greenhouse situation.

I am sure that many on the forum will have other suggestions too.

Hope this helps

Tight....