I have a whitefly infestation on my broccoli, all the leaves were hanging today, I already tried to treat in the last couple of days with 1/1 oil water in spray bottle and soap and water mix in spray bottle, seems like nothing helps, do you know a better treatment? I don't want to use chemicals.
I know your post was awhile ago but I thought I'd post anyways.
When it comes to our garden, I use two routes for whiteflies. Firstly, find the yellow sticky pads. They are essentially pieces of thin cardboard with an adhesive on one side. Hang these around plants and place some pieces on substrate. These are very effective at catching any flying or hopping organisms.
Secondly, pick up some neem oil and spray, spray, spray. These little suckers seem to stick around. I have found that it is best to spray plants when they are not in direct light. The refraction of light off the droplets can sometimes burn tissue.
The last thing that I can think of is, quite simply, ladybugs. The strategy with ladybugs is obviously keeping them on the plants. The easiest way to do this is by having the area enclosed, or to tie cheesecloth over the plant and release ladybugs inside.