The Banana Farmer doesn't believe in popping Bloons, but he's an expert when it comes to collecting bananas. Place him near your Banana Farms and he'll save you from the trouble of manually collecting the bananas.
More recently, on March 2016, the Monkey Farmer became a tower for Bloons Monkey City Mobile. However, it costs $1.99 USD for each Banana Barn and the Farmer itself is free to place when capturing tiles. Along with its original capability of collecting bananas and crates in-game, each Banana Barn building purchased provides a 10% increased capacity to each Banana Farm in the city, thus the effect can stack with other Barns.
On October 27th 2016, the Monkey Farmer became available on Bloons TD Battles Mobile as a one-use tower, and costs 100 each. It can be used only if the player chooses Banana Farms along the battle.
Oddly, even though it says that the Monkey Farmer is tired of picking up bananas, in its artwork he appears to be very happy (since he's being paid to do it; his salary does not affect your income, though).
It was released again in Bloons TD 5 Mobile because it is much harder to tap the bananas instead of moving your mouse on them and can be pretty risky because sometimes a tap might miss a banana and can spoil.
It may be efficient only if the given Specialty Building is a better choice in case of limited tower selection.
In Bloons Monkey City Mobile, if you have the Banana Replicator special item which increases the capacity of the player's first Farm by 150 in the city, placing a Banana Barn will give a 115 capacity increase to the first Farm instead of 100.
Although Farmers does not pop any Bloons, they have do have a pop count in their tower interface.