Prospects of Epichloë endophytes on fall armyworm growth and survival in tall fescue

Abstract

Fall armyworm (Spodoptera frugiperda) larvae are detrimental pests to many crops in the Southeastern USA, including tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.), grown for turf and forage. In most natural and managed ecosystems, tall fescue plants harbour an Epichloë endophyte that imparts protection to the grass from abiotic and biotic stresses, including insect deterrence. Enhancing tall fescue resistance to fall armyworms may be achieved by identifying Epichloë endophyte strains that exhibit antibiosis or antixenosis. In this study, we inoculated 22 Epichloë strains (16 nontoxic and 6 toxic), isolated from tall fescue collections of various origins, into an endophyte-free continental-type tall fescue cultivar and a Mediterranean-type tall fescue cultivar. Leaves from each strain × host combination were used in feeding studies with fall armyworm larvae. We investigated the effect of different strain × host combinations on fall armyworm development by measuring larval weight gain, days to pupation, and survival in the laboratory. Complementary ratings of defoliation were conducted in a field infested with fall armyworm to assess pest damage under natural conditions. The Mediterranean-type tall fescue, in combination with most strains, showed detrimental effects on larval development. Two endophyte strains (one capable of producing mammalian-toxic ergot alkaloids and the other not capable of producing ergot alkaloids) significantly reduced fall armyworm larval development and minimised defoliation in the field. These will be characterised further for use in integrated pest management.