Effects of Multi-Generational Rearing on Job's Tears on the Performance and Host Plant Preference of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

The fall armyworm (FAW), Spodoptera frugiperda, is a highly polyphagous pest posing a major threat to Poaceae crops, particularly corn (Zea mays), in China. However, its ability to adapt to Job's tears (Coix lacryma-jobi), an edible and medicinal Poaceae species, under continuous rearing remains insufficiently understood. In this study, FAW survival, development, and reproduction were assessed over eight generations on two cultivars of Job's tears, 'Cuiyi 1' and 'Puyi 6'. Feeding and oviposition preferences were also examined in FAW populations reared on 'Puyi 6' by offering corn and 'Puyi 6' as hosts. Sustained rearing for five to eight generations on both cultivars significantly increased population fitness, with greater improvements observed in the 'Puyi 6' group. FAW reared on corn or 'Puyi 6' for two generations exhibited strong preferences for corn, whereas those reared on 'Puyi 6' for five to eight generations showed no significant host preference. These findings suggest that transgenerational adaptation markedly improved FAW performance and acceptance of Job's tears, underscoring the need for intensified monitoring of FAW dynamics during the cultivation of Job's tears.

Keywords: Coix lacryma-jobi; Zea mays; acclimation; fall armyworm; host plant adaptation; life table; population projection.

Figure 1

Effects of continuous rearing on the body weight of 5th instar larvae (A) and pupae (B) of FAW fed on corn for two generations (CoJ-F2) and continuously reared on Job’s tears cultivars ‘Puyi 6’ for two (JtP-F2) and eight generations (JtP-F8). Different letters above the bar indicate significant differences between treatments for female or male individuals (generalized linear model with gamma distribution and two-way ANOVA followed by Tukey’s test).

Figure 2

Age-stage specific survival rate (s_xj) of FAW fed on corn for two generations (A) and continuously reared on Job’s tears cultivars ‘Cuiyi 1’ (B–D) and ‘Puyi 6’ (E–G) for eight generations. Panels represent different generations: F2 (B,E), F5 (C,F), and F8 (D,G).

Figure 3

Age-specific survival rate (l_x), female age-stage specific fecundity (f_x,female), and age-specific fecundity (m_x) and net maternity (l_xm_x) of FAW reared on corn for two generations (A) and continuously reared on Job’s tears cultivars ‘Cuiyi 1’ (B–D) and ‘Puyi 6’ (E–G) for eight generations. Panels represent different generations: F2 (B,E), F5 (C,F), and F8 (D,G). The points in the l_x curves indicate the age (in days) at which the survival rate drop below 50%: days 37, 42, 33, 38, 41, 35, and 35 in panels (A–G), respectively.

Figure 4

Age-stage life expectancy (e_xj) of FAW reared on corn for two generations (A) and continuously reared on Job’s tears cultivars ‘Cuiyi 1’ (B–D) and ‘Puyi 6’ (E–G) for eight generations. Panels represent different generations: F2 (B,E), F5 (C,F), and F8 (D,G).

Figure 5

Age-stage reproductive value (v_xj) of FAW reared on corn for two generations (A) and continuously reared on Job’s tears cultivars ‘Cuiyi 1’ (B–D) and ‘Puyi 6’ (E–G) for eight generations. Panels represent different generations: F2 (B,E), F5 (C,F), and F8 (D,G).

Figure 6

Total population size projection of FAW reared on corn for two generations (CoJ F2) and continuously reared on Job’s tears cultivars ‘Cuiyi 1’ (A) and ‘Puyi 6’ (B) for eight generations (JtC F2, F5, and F8; JtP F2, F5, and F8). Total population size is shown as the mean (line) ± 95% confidence interval (shaded area).

Figure 7

Effects of continuous rearing on feeding (A) and oviposition (B) preference of FAW reared on corn for two generations (CoJ–F2) and continuously reared on Job’s tears cultivar ‘Puyi 6’ for two, five, and eight generations (JtP–F2, –F5, and –F8). ns, *, and ** represent p > 0.05, <0.05, and <0.01, respectively (Quade test).