Effect of Plant Water Status on Defoliation of Pima Cotton

Abstract

A study was conducted at the University of Arizona Maricopa Agricultural Center, Maricopa, AZ in 1994 to determine the influence of plant water status at the time of defoliation on effectiveness of defoliants and yield of Pima cotton. Several irrigation termination dates were used to achieve different levels of plant water stress at the time defoliants were applied. A single application of defoliants did not provide adequate defoliation under the conditions of this test. The earliest irrigation termination date resulted in the highest defoliation percentage. High CWSI values at the time defoliants were applied were related to the highest defoliation percentages, but were not necessarily related to satisfactory defoliation. The CWSI appears to have limited value as a guide to determine when to defoliate Pima cotton.