One may clear stones [from a field] until Rosh Hashanah. One may prune [trees], thin [them], and cut away [their] decay until Rosh Hashanah. R’ Yehoshua says: Like the thinning and cutting away decay of the fifth, so is that of the sixth. R’ Shimon says: As long as I am permitted work of the tree, I am permitted to cut away its decay.