Resistance of zoysiagrass (Zoysia spp.) to fall armyworm (Lepidoptera: Noctuidae): Leaf tensile strength and cell wall components

Leaf toughness and high levels of detergent fiber, lignin and silica in leaf sheaths have been associated with insect resistance in many crops. Experiments were conducted on the effects of sample date and level of N treatment on the concentrations of lignin and silica and on tensile strength of zoysiagrasses (Zoysia spp.) leaves to compare their relationship to fall armyworm [Spodoptera frugiperda] host resistance. Six zoysiagrass cultivars ‘Cavalier’, ‘Crowne’, ‘Emerald’, 'El Toro’, ‘Meyer’ and ‘Palisades’ were planted on a fine, montmorillontic, thermic Vertic Albaqualfs soil at the Texas A&M Univ. Turfgrass Field Laboratory in College Station, TX. A randomized split-plot design with four reps and with N applied as (NH4)2SO4 at 12.2 kg and 48.9 kg of N ha-1 month-1 throughout the growing season was used. Fiber analysis supported literature reports that cell wall structural components are associated with insect resistance. This study demonstrated that lignin concentration and leaf tensile strength were positively correlated with fall armyworm mortality determined by two types of feeding experiments and that cell wall and hemicellulose concentration in these Zoysia cultivars were positively correlated with applied N.