Worldwide, potato (Solanum tuberosum L.) crops cover 18×10 6 ha, corresponding to a production of 314× 10 6 t. The importance of this crop makes it crucial to control production losses and quality defects due to foliar injury, whether by natural or mechanical causes. The artificial defoliation of potatoes is a common technique used to investigate the correlation between damage caused by either hail or insects and yield. The aim of this study was to evaluate simulated hail damage on different cultivar potatoes of varying maturity to quantify the commercial yield reduction attributable to different defoliation levels through the potato crop cycle. Eight trials were carried out in the Central Ebro Valley (northern Spain) over a period of 4 years with three potato cultivars: Jaerla, Red-Pontiac, and Baraka. Four levels of defoliation (no defoliation, slight defoliation, medium defoliation, and high defoliation) were carried out in several phenological stages. The crop yield losses for each level of defoliation were calculated by correlating the percentage of defoliation applied and the resulting percentage of yield loss. Yield reduction equations were calculated for each trial and phenological stage. Damaged produced during tuber formation or flowering considerably reduced yield. In contrast, defoliations after tubers had completed growth barely affected yields. Differences among cultivars with respect to yield losses were noted regardless of location and year. The early cultivar (Jaerla) recovered worse than the longer-cycle varieties (Red Pontiac and Baraka) as concerns defoliation effects. Effects on yield were similar at the different locations. The regression equations presented may be used for modeling the yield reduction due to defoliation treatments caused by different biotic and abiotic agents.Resumen En todo el mundo, los cultivos de papa (Solanum tuberosum L.) cubren 18×10 6 ha, lo que corresponde a una producción de 314×10 6 t. La importancia de este cultivo hace crucial el control de las pérdidas de producción y de los defectos en calidad debido al daño foliar, ya fuera por causas naturales o mecánicas. La defoliación artificial de papa es una técnica común usada para investigar la correlación entre el daño causado por granizo o insectos y rendimiento. El propósito de este estudio fue evaluar el daño simulado por granizo en diferentes variedades de papa de diversa madurez, para cuantificar la reducción comercial en rendimiento atribuible a diferentes niveles de defoliación a lo largo del ciclo de cultivo de la papa. Se hicieron ocho ensayos en el valle central del Ebro (al norte de España) en un período de cuatro años con tres variedades de papa: Jaerla, Red-Pontiac, y Baraka. Se efectuaron cuatro niveles de defoliación (sin defoliación, ligera, media, y alta defoliación) en varios estados fenológicos. Se calcularon las pérdidas en el rendimiento del cultivo para cada nivel de defoliación, mediante la correlación del porcentaje de defoliación aplicado y el porcentaje resultante de pérdida en el rendimien...
