Question
Just found this white powder like substance on several stems of my rose bush. It looks like it is causing the blooms to dry up.  What type spray or chemical can I use for this.

Answer
Your roses have got a fungal disease called mildew. Mix 1 tablespoon of baking soda to 2 quarts of water and spray every three days. If the problem doesn't go away then spray daily until it does. Also water your roses well with a hose and make sure they really get a lot of water. Mildew is caused when conditions are right for it, but using a sprinkler ten to spread and encourage it far more because the leaves get wet. If baking soda doesn't get rid of it then conditions are ideal for it to spread so  use any rose spray that is for mildew.