Susceptibility of shallots to the timing and severity of leaf damage

The study investigated the response of shallots to different levels of defoliation at different growth stages. The effect of cutting off 50 %, 75 %, and 100 % of leaves of four, six, and eight week old shallot plants was assessed. Defoliation at an early stage of growth, i.e. three-leaf stage imposed stressful conditions, and initially reduced growth rate. Whilst lateral bud numbers increased with the severity of defoliation in four week old shallots, lateral shoots and bulb number decreased. There was significant delay in maturity and a reduction in bulb size and weight in shallots defoliated at six weeks. Six weeks old shallots defoliated at 100% recorded the lowest sucrose content of 6%. Numbers of fresh bulb scales was significantly decreased with increasing defoliation and growth. The effect of defoliation on growth, yield and quality depended on the growth stage of the crop. However, 50% defoliation at all growth stages gave appreciable yield and bulb quality compared with the undefoliated control in this trial.