Helicopter Instructor pilot with student reported a NMAC with an agricultural aircraft while maneuvering requiring the Instructor to take evasive action to avoid a collision.

Narrative

On the morning of Day 0; Aircraft X; a single military TH-1H conducting student training departed on a heading of 130. Upon clearing the tree line at the landing zone (approximately 50 ft AGL) the instructor pilot of Aircraft X had to immediately take controls from the student pilot in order to execute a rapid 90 degree AOB turn at full left deflection on the cyclic in order to avoid a single; Air Tractor AT-300 also at 50 ft AGL; on a heading of 230; flying at an airspeed of approximately 120 knots. Aircraft X was able to safely maneuver away from the AT-300. A controllability check was accomplished by Aircraft X to ensure all flight controls were operating correctly.Upon termination of the sortie; the instructor pilot of Aircraft X was able to contact the pilot of the AT-300. The civilian pilot was aware of the location and said that he was daydreaming and was looking at a cotton field prior to finally observing Aircraft X maneuvering away. He said that he made a left bank to avoid the collision as well. After discussing ways to prevent a future midair collision; the pilot of the AT-300 said that he will monitor XXX.X and will respond to any military aircraft if they let him know where they are operating.