There's a lot to consider when replacing an important tree
I lost a Bradford pear tree in my front yard two years ago. Bradford pears are beautiful trees but have notoriously weak crotches where limbs can be torn off by heavy snow or high winds. My tree succumbed to both, so I had to look for a replacement. I'm afraid that with last year's discovery of Emerald Ash Borer in Rock County we'll eventually see many homeowners looking for new trees.
I first looked around my neighborhood to see which trees are the most popular (besides ash, of course). My neighborhood has a lot of maples, birches, oaks, crab apples, lindens and pears. Those are definitely the ones I won't plant. Not that they aren't beautiful trees – they really are, but I would like to see more diversity. The problem of planting too many of the same type of tree in a neighborhood is the risk of disease sweeping through and killing them all. We've seen this in the past with Dutch Elm Disease and now Emerald Ash Borer.
Rotary Botanical Gardens has recently created a neat display of beautiful trees that would be great alternatives to ash trees. It is located in the main parking lot with signage that describes each tree. The Janesville Shade Tree Advisory Committee is another good source of local information. Also, Dr. Laura Jull of UW-Madison has a great listing of ash alternatives at labs.russell.wisc.edu/eab/files/2012/03/Alternatives-to-Ash-for-Homeowners.pdf.
I finally decided on a ginkgo ('Autumn Gold') for my front yard. This is a very hardy tree that has few disease or pest problems and really cool leaves. The leaves turn bright yellow in the fall and usually drop all at once (nice for raking up!). It is essential to buy a male tree because the females produce fruit with a strong odor likened to “vomit”. I imagine all reliable gardening centers would only carry the male types.
Is there a new tree in your future?