colloidal phosphate - what's the best source?

I've had a problem with whiteflies for years. I've gotten it under control somewhat by removing some of the plants that were most susceptible, removing infected foliage when I can, and by spraying the worst infestations with insecticidal soap. That's way too much work.

My Texas Bug Book says that whitefly infestations usually mean that your soil is low in phosphate and that if you add colloidal phosphate, you won't have a problem anymore. OK, great, where do I find this phosphate? Please help! Thanks!

Elphaba, as far as I know colloidal phosphate is basically natural rock phosphate, and you can find it at most organic nurseries, here is a link to different sources.
http://www.google.com/search?q=rock+phosphate&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
Josephine.

Thanks Josephine! I'm finally getting my ceiling fixed from Ike damage and it's costing $500 more than the insurance gave me for it, so I'm probably going to have to wait on most gardening projects for a while! Darn it! Thanks for the info. I wasn't sure at all what it was!

Sorry you are having extra expenses from the hurricane, house repairs are sooo expensive!!!
Have a Happy Thanksgiving anyway.
Josephine.

Phosphates are generally either Hard Rock Phosphate (most common) or Soft Rock Phosphate, which is a by-product of phosphate mining and far less available. When rock phosphate is dug and crushed, the powdery residue is washed off. It is pumped into ponds to dry, and sold as SRP. It is colloidal phosphate, and is readily-available phosphate in the soil. Regular phosphate can take up to 5 years to become available to plants.

I buy SRP as CalPhos, $10.50 for 50 pound bag.