I had never heard of "weed screed" so I googled it. Well it seems to have something to do with marijuana. Hum! Seriously I am only sending this because I have never heard of a weed screed on a home. Hope to be enlightened.

Its weep screed.

Thanks for the correction. The problem is, I never heard of "weep screed" either!

Weep screeds are long perforated metal strips that are installed along the bottom of exterior walls to allow any moisture that penetrates the siding (but not the black paper or other moisture barrier) to escape by dripping out the bottom. I don't know the construction of your house, but it's unlikely that defective flashing on the roof would cause excessive moisture to get into the exterior walls. There are a few possibilities. Depending on the type of siding you have and your climate, it's normal to have some moisture get through the siding (especially stucco) so the weep screed is doing it's job if some is coming out. Rust means either that it got scratched or the finish was defective or maybe there is an opening somewhere on the wall that is causing excessive moisture to penetrate. Is the rust localized or is it all along the screed?

http://www.netfunny.com/rhf/jokes/91q2/contract.html
http://www.ownerbuildersolutions.com/glossary_index.htm

Rusted weep screeds could be caused by a number of different scenarios. There are some weep screeds on the market today that are called "economy" weep screeds. These type of weep screeds may not be 26 gauge or have a G60 galvanized coating. Lawn sprinklers may be too close to the weep screed thus causing undue water to spray up at the weep screed. Short eaves can also cause water run off to splash too close to the foundation and thus keep the weep screed wet.