The bark is peeling off of what I think is a yucca tree. In addition, white things have sprouted from the trunk. Is this a fungus or something else? How should it be treated? It is very hot here in the summer. The tree is 6 years old. Two others were planted at the same time and seem to be okay. They are watered (by drip) 3/days a week for 20 mins. each day (reduced in the winter).
It could in fact be a fungus or even pests. I would lean towards fungus though, as you water quite often and yuccas are drought tolerant plants. They need watering only when the top inch or so of soil has become dry. If the stem (trunk) is soft or has a smell to it, then it could be bacterial soft rot, which will simply kill it as there is no cure. However, if the stem or trunk is still firm to the touch, a fungus infection may be your culprit. Neem oil can help with this, as well as for any insect pests that may be attributing to the problem.