When host-plant resistance to a pest leads to higher plant damage
The effects of the association between grasses and fungal endophytes on orthopterans are very poorly studied although they are important grassland pests. Here, the endemic New Zealand weta, Hemiandrus sp. ‘promontorius’, and Festulolium loliaceum infected with Epichloë uncinata, were used to study the effect of endophyte-mediated resistance in grasses on this large orthopteran insect in the laboratory, and the effects of this interaction on the grass. The insect was presented with F. loliaceum with and without E. uncinata infection in no-choice and paired choice experiments. Other controls were Epichloë festucae-infected Festuca rubra and endophyte-free Lolium perenne. In no-choice experiments, persistent attempts by the insect to graze the endophyte-infected grasses (but promptly abandoning them) resulted in a significantly higher number of plants lost due to excision at their stems after the first bite (P = 0.004). The inability of affected grasses to compensate for the lost biomass resulted in a lack of significant difference between the dry biomass of endophyte-infected and endophyte-free controls (P = 0.206). However, in choice experiments, there was a preference for the endophyte-free controls when they were paired with the endophyte-infected grasses (P < 0.05). The current work shows that endophyte-infected grasses can sustain high plant losses when attacked by an orthopteran insect in the absence of an alternative food source. This contrasts other endophyte/herbivory experiments in which high herbivory occurs because chemical plant defences are at a low concentration or the endophytes have other non-toxin roles in the plant.
KeywordsEpichloë uncinata Loline alkaloids Festulolium loliaceum Biomass loss Orthoptera Pest management
This study was funded by New Zealand Government’s Callaghan Innovation PhD Research and Development Fellowship Grant (Project no. CONB201) in collaboration with Constellation Brands NZ and CropMark Seeds Ltd., Christchurch. The authors gratefully acknowledge the support of Joanne Brady of Constellation Brands NZ. The grass seeds used in this study and the service of testing for loline alkaloids were generously provided by Brian Patchett and Tim Gillanders of CropMark Seeds Ltd.
This study was funded by New Zealand Government’s Callaghan Innovation PhD Research and Development Fellowship Grant (Project number CONB 201).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with animals performed by any of the authors.
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