Arthropod diversity and abundance in tall fescue pastures containing novel endophytes

Tall fescue (Lolium arundinaceum) pasture grass frequently contains a wild endophyte fungus (Neotyphodium coenophialum) that intoxicates livestock due to its production of ergot alkaloids, yet two other alkaloid fungal products (loline and peramine) are non-toxic and help protect the plant against environmental stress from drought or grazing, and all three alkaloid groups may protect against insect herbivory. Novel endophytes lacking ergot alkaloids have been incorporated into tall fescue, rendering them safer for livestock but potentially more susceptible to insect pests. Furthermore, arthropod predators and parasitoids could be harmed by novel endophyte alkaloids retained in herbivorous prey, potentially influencing pest populations indirectly. Tall fescue pastures were vacuum sampled five times in two years to collect arthropods on four grass/endophyte associations: (1) ‘Kentucky 31’/wild-type, (2) ‘Jesup’/Max-Q, (3) ‘KYFA9301’/AR584, and (4) ‘KYFA9301’/endophyte free. Two adult leafhopper species (Endria inimica, Psammotettix striatus) were consistently more numerous on endophyte free grass, as were Typhlocybinae leafhoppers at one evaluation. Novel endophyte strains generally retained resistance similar to the wild-type. Aphrodes spp. leafhopper nymphs were more numerous on wild than on novel endophyte, and on AR584 compared with Max-Q. Other taxonomic groups did not differ in abundance, including other hemipterans (Cicadellidae, Delphacidae), predatory arthropods (Araneae, Carabidae, Coccinellidae, Staphylinidae), leafhopper parasitoids (Dryinidae), chewing insects (Acrididae, Gryllidae, Tettigoniidae), and other groups (Elateridae, Phalacridae). Lepidoptera larvae and flea beetle numbers (Chrysomelidae) were each higher on wild endophyte at one evaluation. The severity of pest outbreaks is not likely to increase with use of novel endophyte compared with the wild-type.