Hi Paul. According to Dirr, if the fruit is smaller than 2 inches, it is a Crabapple. That being said, there are dozens of Malus species...I did find this info from Micheal Kuhns...he seems to have the definitive work on trees of Utah. This PDF is from USU and deals strictly with Malus species in Utah...with pictures. I hope it is useful to you.
http://www.treebrowser.org/ass...
