The crop monitoring program COTMAN uses the concept of 350 heat units after anthesis of the last effective flower population at NAWF=5 for termination of insecticide applications. It has been reported that terminating insecticides at 350 heat units after NAWF=5 results in a higher yield than when terminating at either before or after 350 heat units, although the evidence for this is lacking. It is hypothesized that insect damage to upper canopy (above NAWF=5) squares results in improved partitioning of carbon to lower developing bolls. Three field studies and a ¹⁴C labeling study were conducted to evaluate this hypothesis. Treatments consisted of a control with no fruit removal, and a simulated fruit damage (hand removal) of all upper canopy squares at approximately 250, 350 and 450 heat units after NAWF=5. This was related to differential movement of ¹⁴C, particularly in the 350 heat unit treatment, from upper canopy leaves with squares removed to bolls developing below the area of square removal. The differential movement of ¹⁴C supports the field study and our hypothesis that available carbohydrates from the upper canopy source leaves were translocated to alternative sinks such as bolls developing in the upper part of the canopy. The data supports the COTMAN concept of insecticide termination at 350 heat units after NAWF.