Arthropod abundance in tall fescue, Lolium arundinaceum, pastures containing novel ‘safe’ endophytes

Abstract

Poor livestock performance on tall fescue is linked to infection by a fungal endophyte that enhances grass resistance to stress, including herbivory, while producing ergot alkaloids toxic to vertebrate grazers. Novel ‘safe’ endophyte/grass associations produce no ergot alkaloids yet retain stand persistence, but they could be more susceptible to insect outbreaks. We tested the hypothesis that grass‐feeding insects are more abundant in novel endophyte pastures compared with those containing common endophyte. Above‐ and below‐ground herbivores were sampled across two growing seasons in pastures containing common strain endophyte (KY31), novel endophytes (MaxQ or AR584) or endophyte free. We also sampled natural enemies as an indicator of possible tritrophic effects. With a few exceptions, numbers of predatory, chewing (grasshoppers, crickets, caterpillars) or sucking insects (leafhoppers, planthoppers) were similar in common and novel endophyte pastures. Contrary to our hypothesis, Aphrodes spp. leafhoppers were more abundant in KY31 than other pasture types in 2008; their nymphs also were more abundant in KY31 than in MaxQ in 2009. Adults (but not total numbers or nymphs) of another leafhopper, Psammotettix striatus, were less abundant in KY31 than other pasture types in 2009. Popillia japonica and Cyclocephala spp. grubs did not differ in density, weight or instar among the endophyte‐containing associations. In feeding assays, armyworm (Mythimna unipuncta) survival was higher on MaxQ and NE9301, and weight gain was higher on NE9301, suggesting armyworm outbreaks could be more severe on such grasses, but that result may not be attributable solely to alkaloids because common strain and endophyte‐free grasses did not differ in either parameter. Caterpillar abundance did not differ among pasture types in the field. Our results suggest that re‐seeding common strain endophytic pastures with livestock‐safe novel endophyte/grass associations to alleviate fescue toxicosis is unlikely to promote markedly higher populations of plant‐feeding insects.

Evaluation of ‘Jackal’ AR601 (Avanex) and Kentucky‐31 Endophytic Tall Fescues for Suppressing Types of Invertebrates that Contribute to Bird Strike Hazard at Airports

“…We acknowledge that our study, conducted in one non–airport location, is not necessarily indicative of how Avanex would affect invertebrate communities across different regions, soil types, and environmental conditions. Nevertheless, our findings are consistent with other field studies in North America (Davidson and Potter, 1995; Rudgers and Clay, 2007; Keathley and Potter, 2012) and Europe (Vesterlund et al, 2011), which showed little difference in macroinvertebrate abundance in tall fescue swards with or without endophyte. Although endophytic tall fescues, including Avanex and KY‐31, might deter geese through learned avoidance, this study suggests their effects on grass‐adapted invertebrates are probably too weak to significantly reduce the food supply for insectivorous birds at airports.…”

“…For example, only four of 27 leafhopper species were less abundant in E+ than in E− tall fescue pastures (Muegge et al, 1991). Grass‐feeding caterpillars do tend to grow more slowly on E+ than on E− tall fescue (Clay et al, 1985; Davidson and Potter, 1995; Williamson and Potter, 1997; Rudgers and Clay, 2007; Keathley and Potter, 2012; this study) but it seems doubtful that would discourage bird foraging.…”

“…Adult scarabs, too, attract birds associated with strike hazard (Buckley and McCarthy, 1994; Bernhardt et al, 2010; Washburn et al, 2011). Endophytes tend to have weak or no effects on abundance of grubs, earthworms, or other soil biota (Potter et al, 1992; Davidson and Potter, 1995; Koppenhöfer et al, 2003; Popay and Jensen, 2005; Lemons et al, 2005; Rudgers and Clay, 2007; Keathley and Potter, 2012), which is expected given their localization in aboveground tissues. Endophytic alkaloids appear to become attenuated up through the food web and to have little or no effect on field abundance of predatory insects and spiders (Davidson and Potter, 1995; Rudgers and Clay, 2007; Keathley and Potter, 2012; this study).…”

“…Other alkaloids, namely lolines and peramine, are active against invertebrates (Schardl et al, 2013). The magnitude of those effects varies among species and feeding guilds (Breen, 1994;Rudgers and Clay, 2007;Vesterlund et al, 2011;Keathley and Potter, 2012). Alkaloid production and expression of endophyte-mediated resistance can also vary depending on the particular grass genotype ´ endophyte haplotype combination (Baldauf et al, 2011).…”

Integrating vibrational signals, mitochondrial DNA and morphology for species determination in the genus Aphrodes (Hemiptera: Cicadellidae)

“…The objective of the present paper is to provide a more comprehensive analysis of Aphrodes using multiple criteria (the iterative approach sensu Yeates et al , ) in order to provide the information needed for reliable species identification, which is clearly needed. Besides being included in molecular and morphological phylogenetic studies (Dietrich et al , ; Zahniser & Dietrich, , ), Aphrodes species are often collected in ecological studies due to their widespread distribution and abundance (Brown et al , ; Hollier et al , ; Jobin et al , ; Huusela‐Veistola & Vasarainen, ; Eyre et al , , ; Eyre, ; Fisher Barham & Stewart, ; Morris et al , ; Nickel & Achtziger, ; Strauss & Biedermann, , ; Kattwinkel et al , , ; Keathley & Potter, ; Körösi et al , ; Schuch et al , ) and some of them are even considered to be indicator species (Maczey et al , ; Trivellone et al , ). They have also been included as potential vectors in phytoplasma and mycoplasma transmission studies (Denes & Sinha, ; Carraro et al , ; Bressan et al , ; Riedle‐Bauer et al , ).…”