[jrasicmark]

It is an odd gag. My guess is we're supposed to assume the adult told the kid he shouldn't be stealing pears anyway, so I'm assuming the gag is that the kid didn't listen to the adult and found a way to get the pear anyway.
In Jack Markow's classic, "The Cartoonist's and Gag Writer's Handbook", one of the gag writer's tropes is to have a character come up with an unusual and unexpected solution to a problem, often using objects in ways they were never designed to be used. I suspect that's what the cartoonist was aiming for here, but fell short since a ladder really isn't an unusual solution for this problem. The only unusual part is that the ladder is broken so that it's just the right size to reach the pear. Maybe we're supposed to guess the kid broke the ladder himself, but that's expecting too much of the reader in my opinion.

Link to the book: Mon Journal 1893-01-21