Assessing the sensitivity of onion ( Allium cepa ) cultivars to defoliation levels across different growth stages

Onion (Allium cepa) yield is susceptible to the occurrence of climatic events such as hail, which can decrease the leaf area of plants and the yield and quality of bulbs. The study aimed to evaluate whether defoliation levels at different development stages of the onion cultivars ‘Ômega’ and ‘Caeté’ affect bulb yield and quality. Three experiments were carried out in the 2019/2020 and 2020/2021 growing seasons, in Lebon Régis, Santa Catarina, Southern Region of Brazil. Five onion defoliation timings (50, 70, 90, 110, and 130 days after planting – DAP) and four defoliation levels (33, 50, 67, and 100% defoliation) were evaluated. The increase in defoliation levels reduced the marketable yield of both cultivars, especially when it occurred between 90 and 110 DAP. With 100% defoliation, there is a 55% reduction in marketable yield (33.9 t ha−1). These findings are unprecedented in subtropical regions and underscore the need to develop management strategies to alleviate stress caused by defoliation.