Using bleach to control Powdery Mildew is non productive and much more hazardous to the environment then some of the other harsher, commercial, controls. Baking Soda can be a good control.
Spider Mites become problems in plants when the weather gets hot and dry because they feed on the plants more and that is an aphrodesiac to them sothey mate more and produce more Spider Mites. Increasing the humidity of the affected plant, on a regular basis not just once or even once a week, is needed to help control them. Spraying a 25 percent soluton of rubbing alcohol (already diluted) does littel more than waste your money, time, and energy. Spraying most all pesticides or miticides in an attempt to control these wee buggers actually only kills off any predators and so allows the population of Spider Mites to grow unchecked.
http://www.pubs.ext.vt.edu/444/444-221/444-221.html

Here is a link that might be useful: About Powdery Mildew

I'm worried about your plans for the tree. In particular, the 'massive pruning' you mentioned. Are you aware that heavy pruning of mature trees can cause permanent damage? If the tree is valuable to you, I strongly suggest that you bring in a couple of ISA certified arborists to take a look at it. Anyone who suggests 'topping' as a remedy is a quack, by the way. What else do you think might be wrong with the tree? Is there any way that you could take pictures of the problems?

Bleach, unless diluted quite a bit, can do damage to the foliage and very little to control powdery mildew. It's considered a strong phytotoxic material.

Alcohol is a well known home remedy for spider mites, and I've used it on outdoor plants myself. But you are talking about a couple of plants that can do a pretty darned good job at hiding mites. I've never had this pest on my ice plant, which I have a lot of, and I hope I never do. I DO deal with the pests on Rosemary, however.

I use a sharp spray of water from the hose, making sure I get the underside and interior of the plants when I spray. My goal is to dislodge. I never get rid of all of them, but between that and their predators, we manage to keep them in control. This happens to be a very hot and dry summer for us, and I may end up bringing out the rubbing alcohol before too long, however.

It's difficult to get rid of spidermites but with repeated applications in rotation it is possible. Never use the same product twice in a row. Alternate between 2 products. Always rotate or they will become immune. Below is a link with directions on how I got rid of two spotted spidermites with pictures of all stages of the mites and damage.

Here is a link that might be useful: does this sound like spider mites?

thanks for your help, I posted a new post under "sick walnut tree" with a picasa album for help with the tree, since it could be more than just mites. Any advice appreciated!!!

Your new post is at http://forums.gardenweb.com/forums/load/pests/msg071606224821.html

I added a suggestion there also.

Here is a link that might be useful: your new post & images