Leaf Age and Related Factors Affecting Endophyte-mediated Resistance to Fall Armyworm (Lepidoptera: Noctuidae) in Tall Fescue

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Abstract
Differences in fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), larval preference for and development on fungal endophyte-infected (high incidence of infection) and uninfected (low incidence of infection) tall fescue, Festuca arundinacea Schreb., at three relative leaf ages were examined. Neonate larvae significantly preferred older, uninfected leaves to equivalent age infected leaves and fed more upon them in paired choice tests. Fourth-instar preference and consumption were not affected by infection status of leaves of equivalent age in 6- or 16-h choice tests. Eight-day larval weights were significantly higher for larvae reared on infected older leaves. Percent wet weight of fescue leaves was significantly higher in infected older leaves. Water-soluble carbohydrate and crude protein content did not differ between infected and uninfected leaves at any leaf age, although crude protein was significantly higher in young leaves. Loline alkaloid content was significantly higher in infected leaves and decreased as leaf age increased. The data suggest that both larval age and relative leaf age affect FAW response to endophyte-infected tall fescue.