Hello Skip,
Thank you for using Ask an Expert. You certainly have a problem on your hands. I am sending information that might be helpful.
Tomato wilt diseases have similar symptoms. When wilt is present, the tomato plant will often start to wilt during the hottest part of the day. At first wilts can be easily confused with the plant wilting due to lack of water. For the bacterial wilt disease the plant will wilt from the top down while the two fungi wilts show wilt symptoms starting at the bottom of the plant and moving up. For all the wilts, the leaves will soon turn yellow and then brown. In a short amount of time, it appears that the whole tomato plant has wilted or melted after which the plant soon dies. If you have a tomato plant that you suspect has one of the wilt diseases you can cut the stem and look for brown discoloration. When the stem is cut open, the outer ring of the stem’s inside will be brown while the center remains white. Fusarium wilt will typically have the brown discoloration further up the stem while Verticillium wilt will have discoloration in the stem closer to the ground or soil line. Generally speaking, the wilt diseases have very similar symptoms and in order to differentiate between the diseases you would need a lab or specialist to make a diagnosis. Knowing which wilt disease is infecting your tomato plants is not necessary in the home garden because the control measures are the same. There is no practical or cost effective chemical control to use for preventing or stopping wilt diseases once they occur. The best strategy is to take several preventative measures to keep the wilt diseases from occurring. One way is when purchasing tomato seeds or transplants in the spring, buy varieties with disease resistance. Tomato varieties will have letters that describe what they have resistance to. For example a variety with an “F” and “V” will have resistance to Fusarium (F) and Verticillium (V) wilt diseases. Another common resistance is “N” for nematode resistance. Crop rotations of 4-6 years will reduce the build-up of wilt diseases in the soil. Crop rotations means to not plant the same plant type in the same location every year. If you had a problem with tomato wilts, you would want to not plant tomatoes in the same location for a few years. Instead try a new location and in the area with the wilt problem plant something else. When you plant something else, do not use plants that are closely related to tomatoes (like peppers, potatoes, and eggplants) because these plants are usually susceptible to the same diseases as tomatoes. Instead you would want to plant something that is unrelated to tomatoes, like corn. Sanitation is an important practice for reducing wilt disease problems. When you have tomatoes infected with wilt, be sure to remove and destroy the entire plant (including the roots). When you are finished with your garden at the end of the growing season, clean your garden well by removing all plant debris since many diseases can overwinter on plant material. Grow seedlings on clean soil, or buy transplants from growers who practice good sanitation practices. Be sure to occasionally clean and sanitize garden tools so you prevent carrying disease-infected soil on the tools to a site without soil-borne diseases. If, no matter how many different locations you try you still end up with tomato wilt diseases, you may want to consider planting your tomatoes in containers. Using containers prevents having to deal with the wilt diseases in the soil. Be sure to use professional potting soil to ensure it has been sanitized. Tomato wilt diseases are one of the biggest challenges for home gardens. Nothing is worse than waiting for that first homegrown tomato, only to discover that overnight a wilt disease has taken over your tomato plant. Even though it is a challenge, by being aware of the diseases and following the practices above may help reduce wilt problems to where you can have some luck with growing nice, red tomatoes.                                                                                                                       You also mentioned that you water the tomatoes when it hasn't rained for two days.  It is important to make sure you are not giving them too much water as "water wilt" will start from the top of the plants as well.  If you can not figure out the problem I would suggest taking a the plant to your MSUE Office for a Diagnostician to look at and ID the problem.
Good Luck! 

Hi thanks for the very thorough answer.
If I water them less now, will they come back if it was an overwatering problem?
I still don't know what it is.
I thought this was the way to contact the MSUE diagnostician.
No?
How do I find the MSUE office. I thought this was it.
Thanks
 Skip

Hello again.

Ask an Expert are Master Gardeners who volunteer answering email questions, but sometimes to get a correct answer you should take it to a MSUE Office for a diagnostician to look at it.

At this point, I am not sure if it is water wilt or bacterial wilt and since this has been an ongoing problem I would suggest you check with Oakland County MSUE Office, 1200 N Telegraph Rd., North Office Bdg., 26E, Pontiac, Mi. 48341.                             I don't think the plants will come back at this point, but you really don't have anything to lose. Sorry, I couldn't give you a definite answer. 

Hi Skip,
I just heard from a volunteer at Oakland County Hotline office and at this time they don't have a volunteer that is an expertise in vegetables.  
If you don't mind it would be beneficial for you to send the plant to MSU Diagnostic Lab. I am sending you the link and when you go to that website you will find the information needed to send them the plant, the way to mail it and the cost.

I am sorry for the confusion and I hope you are not too frustrated to continue on the quest to find the problem causing your tomato plants to wilt year after year.

Please check out the website at: MSU Plant and Pest Diagnostic Services.