The objective of this research was to determine if subtle changes in cotton growth could be detected in early stages and followed throughout the season by nodal developmental rates. The procedure was evaluated using seven cultivars representing a range of cotton growth types. Subtle growth effects were caused by two applications of methyl parathion to seedlings. Differences in nodal developmental rates between methyl parathion treated and untreated plants were apparent at 49 days from planting, during pre-flower development, at maximum number of pre-flower limbs, and during postflower development.