Q.ponytail palm
I have an outdoor ponytail palm that is 30 years old and over 20 feet tall. It is developing holes in the arms. What is wrong? Can I save it?
Ponytail Palms are quite resistant to insects and diseases.
The most serious threat to a Ponytail Palm is overwatering or flooding, which can cause root rot and bacterial or fungus diseases.
Leaf Spot, bacterial leaf streak and what your plant may be suffering from--stem rot.
This can be a difficult issue with a large outdoor specimen.
Avoid watering and allow the soil to dry.
If the plant has developed root rot it may not recover and you should take care to make sure the plant does not harm anyone or anything if it should fall over.
https://www.gardeningknowhow.com/houseplants/ponytail-palm/ponytail-palms-outside.htm