the effect of endophyte in perennial ryegrass and tall fescue on red and blackheaded pasture cockchafers

Abstract

Perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) are two of the most productive pasture species grown to feed livestock in Australia. The larvae of redheaded (RHC) (Adoryphorus couloni Burmiester) and blackheaded (BHC) (Accrosidius tasmaniae Hope) cockchafer cause significant damage to these pastures in Australia. If alkaloids produced by endophyte associations could reduce this impact, economic gains would be made. A pot experiment and then a proof of concept seed feeding experiment were undertaken to test the resistance of perennial ryegrass and tall fescue to cockchafer larvae. The objective was to allow larvae to feed on endophyte infected plants, assuming insecticidal alkaloids would be produced and on nil endophyte plants as controls. The plants in the pot experiment were tested for presence or absence of alkaloid endophyte but not for concentration or location in plant parts prior to larvae being introduced. In the seed feeding experiment seed fed to larvae was tested for all known alkaloid concentrations and profiles. The weight difference and mortality of third instar larvae and weight difference of plant root and shoot were measured in the pot experiment. The weight difference and mortality of the third instar larvae and the number and weight of seeds consumed were measured in the seed feeding experiment. There was no significant effect of endophyte treatments on the cockchafer weight change or mortality in either the perennial ryegrass or tall fescue pot or seed feeding experiments. There was a significant difference between cockchafer species (P<0.001) with the larger redheaded larvae consuming more than the blackheaded larvae. It is concluded in both experiments that red and blackheaded cockchafers are not sensitive to endophyte in perennial ryegrass and tall fescue. Endophyte infection can be harmful to livestock and manipulation in plant cultivars can provide insect resistance and drought tolerance which is still a valuable attribute in all areas where cockchafers are not a problem. However, even when cockchafers damage plants, endophyte infection may enhance the ability of these cultivars to recover. Keywords: endophytes, cockchafers, perennial ryegrass, tall fescue