Armyworms and cutworms feed mainly on gramineous hosts and are persistent pests of turfgrass areas and occasional pests of pasture. In the United States the species of armyworm most likely to attack tall fescue is the fall armyworm [Spodoptera frugiperda (J.E. Smith)] (Fig. 9-15). Foliage feeding by this species causes damage in sporadic and sometimes severe outbreaks in the southeastern and Gulf states in late summer and fall. Other species of armyworm in the United States, such as Mythimna unipuncta (Haworth), are more likely to attack field crops of small grains rather than fescue but occasionally occur in turf. In Australia and New Zealand, species of armyworm have the potential to attack tall fescue in pasture, but damage from these species has not been recorded.


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Fig. 9-15. Spodoptera frugiperda. Top left: larva (photo: Fred Baxendale), top right: mature armyworm (photo: Doug Richmond); bottom: damage to tall fescue (photo: Fred Baxendale).


Fig. 9-16. Black cutworms, Agrotis ipsilon (photos: Doug Richmond, Fred Baxendale).


The black cutworm [Agrotis ipsilon (Hufnagel)] (Fig. 9-16) is a worldwide pest in turf but seldom reaches sufficient population densities to cause damage in pasture. Cutworms are subterranean insects and are so-called because of their habit of severing tillers at the base and taking them into their burrows. Their preferred food is creeping bentgrass [Agrostis stolonifera var. palustris (Huds.) Farw.], but tall fescue is an alternative host (Williamson and Potter, 1997).

Effect of Endophyte

Weight gain and development rate of the fall armyworm can be reduced by endophyte infection of tall fescue (Clay et al., 1985, 1993; Hardy et al., 1986). The effect appeared to be age-related, with neonates exhibiting a preference for uninfected leaves, whereas fourth instars consumed equal amounts of E+ and E- material (Hardy et al., 1986). Herbivory by fall armyworm increased the competitiveness of E+ tall fescue relative to orchardgrass (Dactylis glomerata L.) with which it is otherwise a poor competitor (Clay et al., 1993). The loline and the ergot alkaloids may contribute to the response of fall armyworm to endophyte (Clay and Cheplick, 1989; Riedell et al., 1991), but neither of these is essential for resistance (Jones et al., 1997). Other studies, however, have failed to show any major effects of N. coenophialum infection on fall armyworm. Breen (1993b) found no effect on consumption, weight, survival, or development time of third instars, whereas Bultman and Conard (1998) reported a negative effect only on pupal mass and found that endophyte infection increased larval mass and accelerated development. Ball et al. (2006) evaluated several endophyte strains in tall fescue for their effects on fall armyworm. While the fall armyworm larvae showed a feeding preference for E- tall fescue over tall fescue infected with some of the endophyte strains, there were no consistent effects on fall armyworm growth and development. Larval age also influenced the response of the true armyworm, M. unipuncta, to endophyte (Eichenseer and Dahlman, 1993). Endophyte infection of tall fescue appeared to have little or no adverse effects on black cutworm weight gain and development even in trials with neonate larvae (Williamson and Potter, 1997).


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