Effect of intensity and timing of defoliation on seed yield and yield components in oilseed gourd and its implication in insect pests’ sustainable control

Abstract

Dual-purpose cropping for both leaf and seed production can be highly profitable if leaf removal by pests or farmers does not cause significant loss of seed yield. The objective of this study was to access the effect of defoliation intensity and timing on 7 yield and yield components for the cucurbit Lagenaria siceraria. The study was done in 2013 and 2014. Four defoliation intensities (0, 25, 50 and 75%) were applied to the crop at three phenological stages (tendril, flowering and fruit setting stage) in a split plot design. For all the yield traits examined, no significant difference was found between the control and 25% leaf defoliation, whatever the plant phenological stage. However, intense defoliation negatively affected seed production (from 1.99±0.98 t ha-1 with the control to 1.41±1.07 t ha-1 with 75% defoliation), irrespective of the growth stage of the plant. Seed yield decreased when defoliation was applied at advanced phenological stage, varying from a mean of 1.99±0.98 t ha1 (tendril) to 1.55±0.34 t ha-1 (fruit setting). The results suggested that the intensity of defoliation when harvesting the leaves or to trigger the treatment of bottle gourd against leaves damaging pests is about 25%, whatever the timing.

Key words: Defoliation, Lagenaria siceraria, phenological stage, yield