How long does it take for fruit to spoil?

I have had 6 pears waiting on the ground for several days, I don't exactly remember how many. I am waiting for them to spoil so that I can catch an ant.

How long does it take for fruit to spoil?

Fruit doesn't actually spoil; what happens is the last time you harvest a Perfect Fruit tree, one of the fruits it drops will be rotten. Perfect fruit trees can be harvested a random(?) amount of times and the last time you shake it the leaves will all fall off and you should get a rotten fruit instead of one of the perfects. Ordinary fruit left on the ground can be left indefinitely without spoiling, best I'm aware.

Turnips, on the other hand, will spoil a few days after purchasing because of the "stalk market" depends on scarcity. Rotten turnips, while more expensive, may be easier to obtain if your only goal is the bugs that collect on rotten items.