Two Epichloë festucae var. lolii endophytes in Lolium perenne reduce larval populations of the wheat sheath miner, Cerodontha australis

Abstract

The wheat sheath miner, Cerodontha australis Malloch (Diptera: Agromyzidae), is a small leaf-and stem-mining fly that is native to New Zealand and eastern Australia where it feeds on grasses and cereals. Although not considered to be a major insect pest of pastures in New Zealand, it can be abundant during spring and summer in Waikato, New Zealand, and infests tillers of the introduced pasture plant, perennial ryegrass, Lolium perenne L. (Poaceae). Cerodontha australis is not deterred from feeding on L. perenne infected with commercially available strains of the fungal endophyte Epichlo€ e festucae var. lolii, which have been shown to provide protection from a range of other insect pests. In this study, three-pot trials and periodic examination over 18 months of field-collected L. perenne tillers showed that two Epichlo€ e endophyte strains, AR47 and AR48, reduced the survival and feeding damage by C. australis larvae, but there was no evidence of an effect on adult female feeding or oviposition. Compared to other strains of E. festucae var. lolii endophytes tested, plants infected with AR47 and AR48 had fewer and smaller larvae and less larval mining. The number of tillers with mining was reduced in AR47 relative to endophyte-free (Nil) by 57.1% (ranging from 25.0 to 92.5% across trials) and in AR48 by 67.1% (26.3-100%). Larvae in AR47 and AR48 were found further from the base of the tiller where they were less likely to damage the meristem and cause tiller death. The number of larvae and pupae in pseudostems was reduced in AR47 and AR48 compared with Nil by 78.4 and 82.0%, respectively, in the field trial. Very few larvae survived to pupation in AR47 and AR48 plants, with a reduction compared to Nil of over 81.5% in AR47 and over 97% in AR48 in each of the four trials presented here.

Molecular identification of Cerodontha australis (Diptera: Agromyzidae) and its associated pupal endoparasitoids (Hymenoptera)

“…Submission of the COI barcode sequence associated with a C. australis voucher specimen provides a molecular reference that will aid the identification of all life stages of C. australis in future studies and has allowed us to validate our previous informal morphological identifications (Jensen et al 2022; Jensen & Popay 2022). More broadly, by linking a molecular reference with an authoritatively identified voucher specimen, this work contributes to the discussion around, and improvement of, the DNA barcoding repositories.…”

“…We sought confirmation of species identification by combining traditional morphological identification with molecular identification using the 5′ end of the mitochondrial cytochrome c oxidase I subunit gene (COI barcode) (Hebert, Cywinska, et al 2003), to confirm the validity of tentative C. australis identifications conducted during previous research into this leafminer (Jensen et al 2022; Jensen & Popay 2022). Species identification was also sought for associated hymenopteran pupal endoparasitoids.…”