And esrog that wsa stolen or dried out is pasul. If it comes from an ashiera tree or ir hanidachas it is pasul. If it’s the first three years of growth it is orlah and it is pasul. If it is tremah and tameh it is pasul. If it is tremah and is tahar it is kosher but preferably should not be used. If it is deamai, Bais Shami say it’s pasul, and Bais Hillel says it’s kosher. If it is masser sheini in Yerushalyim preferably it should not be used.

Succa 3:6

If on most of the esrog grew a scab-like covering, it’s pittum was taken off, it was peeled, split, or missing anything it is pasul. If the ukatz was taken out or there’s a whole with nothing missing it is kosher. An Ethiopian esrog is pasul. A green esrog Reb Meir says is kosher and Reb Yehuda says it is pasul.