Occurrence of Metarhizium anisopliae in nests and feeding sites of Australian termites

Abstract

A total of 479 samples of nests or feeding sites of 38 species of Australian termite were plated onto a medium selective for isolation of Metarhizium spp. Sixty-seven samples were positive for Metarhizium spp. and a total of 97 isolates of M. anisopliae were obtained. Very few isolates were obtained directly from infected termites. Most isolates were obtained from nest-mound material from eastern Australia. Termite-associated material from the two common mound-building species of termite, Nasutitermes exitiosus and Coptotermes lacteus, provided 75 of the isolates. Similar material from 26 species of termites revealed no Metarhizium. A detailed study of two sites found that some of the Metarhizium isolates found in nest-mound material, including also some M. flavoviride and M. album, were of morphological types also present in adjacent soil. The DNA of isolates from mounds and the adjacent soil were compared using RAPDs and sequence analysis of the ITS region of the nuclear rDNA and the same types were found from both sources. The possible role of the fungus in termite ecology is discussed and it is thought most likely that Metarhizium is only opportunistically a pathogen of termites. Thus, isolates obtained from termite nest material are probably there because of the incorporation of soil into termite nests.