Ask Mr. Smarty Plants

Although Tradescantia is usually relatively free of problems from pests and diseases, it has been noted by Chuan Hong, Extension Plant Pathologist at Hampton Roads AREC that  Tradescantia virginiana (Virginia spiderwort) is attacked by Southern blight, a soil-borne fungus (Sclerotium rolfsii) that causes crown rot.  A search online didn't find a connection between voles and Tradescantia.
The University of Minnesota Extension have an online factsheet about Southern Blight. They say the first symptoms are yellowing and wilting of the lower leaves. Then the leaves start to dieback from the tips and ultimately the succulent stems fall over. The fungus typically attacks the plant just under or at the soil line.  Another sign is a large amount of cottony white thread-like mycelium around this infection point. Control of Southern blight is a challenge in the south where cold weather doesn't slow it down.  Prevention is the best strategy. Inspect all new plants and their associated soil carefully for the symptoms and signs noted above. If you have any doubts, consider putting a new plant in a quarantine area of your garden, where, if it is diseased, the disease can not spread to other plants.
If Southern blight becomes established in your garden, there are some important cultural controls you can implement to reduce the spread of this disease. When dealing with Southern blight, sanitation is particularly important. Fungus spores can be transported around your garden with infected soil. For this reason, carefully clean soil off your tools and even your shoes. Transplanting infested plants is another way the fungus is spread around a garden. Because the fungus can overwinter in mulch, it is helpful to remove mulch from the crowns of the plants. Soil solarization, a process that heats the soil to levels sufficient to kill many fungi, is a control measure used in the south.