Insights into fall armyworm (Spodoptera frugiperda) biology and resistance mechanisms in dual-purpose maize inbred lines

Abstract

The biology of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) was studied on fodder maize cultivar African Tall under room temperature in 2023. The average incubation period was 2.29 ± 0.16 days and the larval duration was 12.95 ± 1.03 days. The larvae underwent five molts, resulting in six instars, and exhibited a total feeding period of 12 days. The pupal period averaged 7.62 ± 0.17 days for males and 8.29 ± 0.57 days for females. Longevity studies revealed that males lived an average of 7.52 ± 0.23 days with food, while females lived 9.65 ± 1.30 days; survival was significantly reduced in the absence of food. The average fecundity per female was 942.8 ± 90.28 eggs, with total life cycle durations of 33.20 ± 2.47 days for females and 30.38 ± 2.66 days for males. Morphometric measurements were also taken. The field experiment was conducted at Dharwad during kharif 2023 to screen 15 dual-purpose maize inbreds along with the cultivar African Tall against FAW. Three inbreds, viz., C 79, PML 36 and PML 46, were categorized as resistant; ten inbreds, CDM 1330, PDI 639, PML 96, PDI 649, PDI 12, PML 105, DDM 2309, CML 565, C 46, PML 85 and African tall, as partially resistant and two inbreds, DDM 2207 and PML 93-2, as susceptible. The resistant inbreds exhibited the lowest larval populations and minimal leaf damage, apparently due to high trichome density, low total soluble sugar and high phenol content. Conversely, susceptible inbreds displayed the opposite biochemical and physical profiles.