As you have lived there a while you should know which trees tend to be late to leaf out. Mesquite is one of the last trees to leaf out, and some individuals can be weeks later than others. If this tree is not late every year, then it's possible it may have become diseased. Mesquite DISEASE is not common and most cause little serious trouble. However, fungal diseases are often unnoticed until a tree dies. CROWN GALL is a possibility. and Spongy Yellow Heart Rot is also a possibility.

I'd give it plenty of time to leaf then look at surounding plants,esp grass. If grass in area die's suspect natural gas leak.

Clara, where do you live ? I am just west of San Antonio and have mesquites all over my yard and they leafed out almost 2 months early. They are over 50 years old, but last year one did not leaf out when all the others did. We figured it had some sort of issue, although we don't know what, and we had arborists come to take it down. We have a LOT of barbecue wood for years to come.

Hmmmm,just West of SA,watch for smoke and smell of brisket. ^_^

usually chicken and steak, klem1. :-)