Feeding and Life History of Spodoptera exigua (Lepidoptera: Noctuidae) on Different Host Plants

Consumption rates, development times, and life table parameters of the beet armyworm, Spodoptera exigua (Hübner), were determined on five host plants: cabbage, Brassica oleracea capitata L; cotton, Gossypium hirsutum L.; bell pepper, Capsicum annuum L.; pigweed, Amaranthus retroflexus L.; and sunflower, Helianthus annuus L. Mean total leaf weight consumed by larvae was highest in cabbage (2.7 g) and lowest in pigweed (1.6 g). The feeding index (pupal weight divided by total weight of leaf tissue consumed) was highest on pigweed, followed by cotton, pepper, sunflower, and cabbage. On all host plants, significant relationships were found between amount of leaf tissue consumed and resulting pupal weight. Likewise, significant relationships were found between pupal weight and subsequent adult fecundity on all host plants. The highest percentage of female progeny was recorded in S. exigua reared on pigweed (62.2%) and the lowest for larvae reared on cabbage (43.6%). Duration of the larval stage was shortest on pigweed (12.4 d) and longest on pepper (18.0 d). Larval survival was highest on pigweed (94.4%) and lowest on cabbage (67.1%). Three key statistics were used to assess performance of S. exigua on the different host plants: 1) feeding index, 2) intrinsic rate of increase, r; and 3) growth index (percentage immature survival divided by immature development time). Using these measures, S. exigua performance was best on pigweed, worst on cabbage, and intermediate on cotton, pepper, and sunflower. We discuss the implications of these findings for control of S. exigua.