Catechin and Condensed Tannin Contents of Leaves and Bolls of Cotton in Relation to Irrigation and Boll Load1

Water deficit has been shown to decrease insect numbers in cotton, especially Lygus hesperus Knight and Heliothis spp. Condensed tannins have antibiotic activity and have been shown to decrease the feeding, growth rate, and survival of Heliothis spp. Condensed tannins are produced from various catechins, and their concentration has been reported to increase in some plants with various stresses, including drought. Therefore, we measured the catechin and tannin contents of leaves and 4‐day‐old bolls in cotton during irrigation cycles and after the final irrigation. We obtained no evidence that water deficit increases the concentration of extractable catechin or tannin in leaves or bolls. Therefore, other factors must be responsible for the suppression of insect activity in dryland cotton or in irrigated cotton during the dry part of the irrigation cycle. Partial defruiting did increase the catechin and tannin contents of leaves and bolls, suggesting that loss of fruit may cause biochemical changes that contribute to insect resistance.