Recovery of Sesame from Defoliation and Growth Terminal Clipping

Crop loss assessment charts and loss adjustments related to hail damage are based on studies that determine the degree of plant recovery from defoliation. Such information is lacking in sesame (Sesamum indicum L.). An irrigated study was conducted in 1989 and 1990 to determine the ability of a nonbranching sesame cultivar to recover from defoliation and growth terminal clipping applied to plants at different growth stages. The treatments included 0, 33, 66, and 100% defoliation levels and clipped vs. nonclipped growth terminals applied at vegetative (37 days after planting, DAP), flowering (48 DAP), and capsule filling (71 DAP in 1989 and 65 DAP in 1990) stages. Average seed yield of the nondefoliated nonclipped (control) treatment was 1523 kg ha⁻¹ in 1989 and 1832 kg ha⁻¹ in 1990. The magnitude of recovery from defoliation and growth terminal clipping was highly dependent on when the treatments were imposed. In the nonclipped treatment, the 33% defoliation treatment produced 90 to 102% as much seed as the control regardless of the growth stage. Seed yield of the 66% defoliation in the nonclipped treatment varied from 85 to 103% of the control when defoliation was imposed before heavy fruiting (54 DAP or earlier). When imposed after heavy fruiting, the 66% defoliation reduced yield by 20% in 1989 and 30% in 1990. The most severe defoliation (100%) in the nonclipped treatment yielded 93, 89, and 34% of the control in 1989 and 77, 72, and 16% of the control in 1990 when applied at the vegetative, flowering, and capsule filling stages, respectively. The magnitude of recovery from defoliation in the clipped treatments also decreased with more advanced growth stage; however, this response was more pronounced in the clipped than the nonclipped treatments. The greatest reduction in seed yield occurred when all leaves were defoliated and the growth terminal removed after heavy fruiting. Contribution of the Texas Agric. Exp. Stn. Technical article no. 31341.