Mohammadali Mirhosseini

The beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae), poses a significant threat to beet plants, adversely affecting their yield. This study assessed the demographic parameters of this pest on seven commercial fodder beet cultivars, including “Kyros”, “1025”, “Geryty”, “Alianka”, “Laciana”, “Kara”, and “Enermax” under controlled laboratory conditions (27 ± 1 °C, 65 ± 5% RH, 16:8 h L: D). We selected 70 eggs, each less than 12 hours old, from a laboratory-reared generation and monitored their development, mortality, and oviposition daily until the death of the last individual. Data were analyzed using age-stage two-sex life table approach. The duration of the immature stages varied significantly among cultivars, with the total developmental period ranging from 23.79 days on “1025” to 33.25 days on “Laciana”. Immature survival rates also differed, with the highest survival recorded for “1025” (88.57%) and the lowest for “Kyros” (37.14%). Net reproductive rates (R0) were highest for “Alianka” (385.81 offspring) and lowest for “Laciana” (110.97 offspring). The intrinsic rate of increase (r) varied across cultivars, with values of 0.149, 0.214, 0.160, 0.180, 0.125, 0.156, and 0.193. Our findings indicate that “1025” is the most susceptible cultivar to the beet armyworm, while “Laciana” is the most resistant. These results are valuable for developing targeted beet armyworm management programs in different fodder beet cultivation regions.