Q.I have a 2 year old with 7 months Soursop tree. I live in Houston Texas. I’m a little sad cause temperature drop to 43 degrees F
for 3 days and all the leaves had fallen. After the third day it warmed up to 75 degrees and I built a 10 foot tall greenhouse f or future frost. Can someone please tell me if my soursop will survive or die ? I grew this soursop tree from seed in a 55 gallon plastic barrel and it’s about 4 feet tall.

The 55 gallon barrel does has good drainage and I fertilizes every 3 months. So it was probably the 3 day rain that made my soursop leaves fall plus the wind at 43 degrees F. So maybe there is a chance that my soursop might survive ?

43 degrees in not a frost, so freezing can be ruled out. Soursop is evergreen, so a cold snap should not cause leaf drop.
I suspect a water management issue, too much or too little. Does the 55 gal drum have a solid bottom, or does it have ample drainage holes in the bottom? If not, root rot could be to blame.
Is the soil porous and drains fast? If so then water deficit/drought stress could be the cause of leaf drop.
Do you fertilize? If not, then nutrient deficiency could cause susceptibility to environmental stress.
Here is an article with more information:
https://www.gardeningknowhow.com/edible/fruits/soursop/soursop-tree-care.htm