Evaluating a novel endophytic grass for suppressing invertebrates that contribute to bird strike risk at airports

Authors: MILLER, DIANA - University Of Kentucky; REDMOND, CARL - University Of Kentucky; Flythe, Michael; POTTER, DANIEL - University Of Kentucky

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2017
Publication Date: 9/7/2017
Citation: Miller, D.M., Redmond, C.T., Flythe, M.D., Potter, D.A. 2017. Evaluating a novel endophytic grass for suppressing invertebrates that contribute to bird strike risk at airports. Crop, Forage & Turfgrass Management. 3(1):1-11.

Interpretive Summary: Some grasses have symbiotic fungi called endophytes. One of the functions that an endophyte can perform for a grass is to produce toxins (e.g. alkaloids) to deter insects and other animals from feeding on the grass. It has been proposed that a grass with high levels of toxic alkaloids could be used to keep insects and other invertebrates off of grass that surround airports. If there were fewer invertebrates, then fewer birds might come to feed on them. These experiments tested two types of tall fescue, Kentucky 31 (a standard lawn and forage fescue) and Avanex® (a fescue reported to have increased alkaloids), for the ability to reduce invertebrates and the birds that feed on them. In this case, alkaloid concentrations were no higher in Avanex than in Kentucky 31. In the laboratory, both grasses were active against an aphid, but effects on caterpillars were more subtle and somewhat stronger for Kentucky 31. The grasses were tested in the field in plots by collecting invertebrates and monitoring bird visits to the plots. In the field, neither grass reduced invertebrates or birds compared to the same cultivars without endophyte. Wild grazing animals, like deer or rabbits, are also a problem at airports. Goats were used as a surrogate for wild grazing animals to determine if Avanex would deter grazing. The goats were offered either grass in short-term preference trials conducted on the plots. The goats grazed both grasses, but preferred Avanex. These results do not support the idea that endophyte-infected grasses can deter wildlife. It is possible that over longer periods of time animals might learn to avoid a particular grass, but that could not be determined from these experiments.

Technical Abstract: BACKGROUND: Tall fescue containing a selected strain of the fungal endophyte Epichlöe coenophiala purported to express high levels of bioactive alkaloids (Avanex®) was recently commercialized for reducing airport bird strike hazard. We compared bioactivity of Avanex and KY 31, a ubiquitous cultivar with wild-type endophyte, against grass-feeding insects and tested the hypothesis that both grasses would significantly reduce field populations of types of invertebrates attractive to insectivorous birds. We also assessed bird visitations and response of goats, surrogates for airport-relevant vertebrate grazers, to field plots with or without endophyte. Integrity of grass-fungal associations was confirmed by immunoblot and alkaloid analyses. RESULTS: Alkaloid concentrations varied seasonally but were no higher in Avanex than in KY 31. Both grasses were active against an endophyte-sensitive aphid, but effects on generalist caterpillars were more subtle and somewhat stronger for KY 31. Neither grass consistently reduced field populations of above- or below-ground macroinvertebrates, or bird visitations, compared to the same cultivars without endophyte. Goats preferred Avanex over KY 31 in short-term feeding trials. CONCLUSION: Although endophytic grasses might deter grass-feeding vertebrates (e.g., geese) through learned aversion, this study suggests their suppression of invertebrates is probably too weak to indirectly reduce abundance of insectivorous birds at airports.