Making an entity make crops grow faster

I am adding Bacillus Subtilis to minecraft.

I need to find a way to make it so that when this entity is existing, it checks if a crop is in a six block radius, and if it is, the entity moves towards the crop, stays there, and while the entity is in collision with the crop, the crop grows faster. after the crop is done growing, the cycle repeats. If there is no crop in a six block radius, the entity wanders around aimlessly like usual.