Host suitability of commercial sugar beet cultivars for the beet armyworm, Spodoptera exigua: an age-stage, two-sex life table analysis

The beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), is a major polyphagous pest of sugar beet ( Beta vulgaris L.) worldwide, causing significant quantitative and qualitative yield losses. In this study, the life history and demographic parameters of S. exigua were evaluated on four commercial sugar beet cultivars (‘Doreta’, ‘Urselina’, ‘Dena’, and ‘Yalda’) under controlled laboratory conditions (26 ± 1°C, 50–60% RH, and 16:8 h L: D photoperiod). Population parameters were estimated using the age-stage, two-sex life table approach. The egg incubation period did not differ significantly among cultivars (approximately 2.00 days; P > 0.05). However, the total preadult developmental time (egg to adult emergence) differed significantly among cultivars and was shortest on ‘Doreta’ and longest on ‘Urselina’. Fecundity varied markedly among cultivars, with the highest value recorded on ‘Yalda’ (402.35 eggs/female) and the lowest on ‘Doreta’ (120.00 eggs/female). The net reproductive rate ( R 0 ) ranged from 51.42 offspring/individual on ‘Doreta’ to 195.42 offspring/individual on ‘Yalda’. The intrinsic rate of increase ( r ) varied significantly from 0.159 day⁻¹ on ‘Doreta’ to 0.199 day⁻¹ on ‘Yalda’. Overall, ‘Yalda’ was the most suitable host for S. exigua population growth, whereas ‘Doreta’ was the least suitable. The reduced performance on ‘Doreta’ suggests lower host suitability rather than strong host plant resistance under laboratory conditions. This cultivar could therefore serve as a useful component in integrated pest management (IPM) programs for sugar beet, although these findings should be validated under field conditions.