Here is a link that provides good information about whiteflies and an interesting concept that using Sevin, as I did, will flare-up and not fix the problem. (UPDATE 7/8. The Sevin killed them)
msucares.com
Basically, it suggests Sevin and other insecticides don't work and kill the beneficially insects that feed on them. Well, I used Sevin spray yesterday and the day before. I will have to check this evening to see if they persist. The one thing to note is that the infestation was/is big. So, if I did kill any benefecial insects, they weren't doing a thing to help up otherwise.
Like I wrote earlier, I never had whiteflies. This has to be the worst year for bugs and now 2 weeks without rain. Tough gardening this year in Maryland. Soon the blight will or will not show its ugly yellow spots.
Here is the complexity of the problem, what do I use? This article suggest Sevin is fine.
This link has some great pictures and details about the whitefiles and treatment http://edis.ifas.ufl.edu/mg254
Here is a bit from the above link:
Who wants to bet I have this variety. I'll be making some home-made soap tonight.
If the whitefly species is hard to control with these products, then it may be the silverleaf species, or QBiotype. Soap or oil sprays are the most effective for homeowners to use against this particular whitefly and are safe to people and the environment. Follow label directions. Thorough coverage on the undersides of the leaves to the point of run-off is especially important when using soap or oil sprays. If a commercial soap or oil is not available, a homemade mixture can be made by mixing 2 tablespoons of dishwashing liquid (do not use those containing a degreaser or an automatic dishwashing soap or detergent) and 2 tablespoons vegetable cooking oil per gallon of water. Repeat at weekly intervals as needed.
The joys of Sevin...We don't have white fly issues (knock on wood), but this year, our extra long and cool spring gave rise to seedcorn maggots. I ended up resorting to using Sevin, in liquid form, on our soil. I really would have preferred not to because we have honeybees, but I was out of options. Fortunately applying it in the evening after the bees went to "bed" helped minimize their exposure. Next year though, I'm going to start everything as transplants to avoid having to use Sevin again.
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