HOST-SPECIFICITY OF MICROSPORIDIA (PROTISTA, MICROSPORA) FROM EUROPEAN POPULATIONS OF LYMANTRIA-DISPAR (LEPIDOPTERA, LYMANTRIIDAE) TO INDIGENOUS NORTH-AMERICAN LEPIDOPTERA

Results of traditional laboratory bioassays may not accurately represe nt ecological (field) host specificity of entomopathogens but, if care fully interpreted, may be used to predict the ecological host specific ity of pathogens being considered for release as classical biological control agents. We conducted laboratory studies designed to evaluate t he physiological host specificity of microsporidia, which are common p rotozoan pathogens of insects. In these studies, 49 nontarget lepidopt eran species indigenous to North America were fed five biotypes of mic rosporidia that occur in European populations of Lymantria dispar but are not found in North American populations of L. dispar. These micros poridia, Microsporidium sp. from Portugal, Microsporidium sp. from Rom ania, Microsporidium sp, from Slovakia, Nosema lymantriae and Endoreti culatus sp. from Portugal, are candidates for release as classical bio logical control agents into L. dispar populations in the United States . The microsporidia produced a variety of responses in the nontarget h osts and, based on these responses, the nontarget hosts were placed in the following categories: (1) no infection (refractory), (2) atypical infections, and (3) heavy infections. Endoreticulatus sp. produced pa tent, host-like infections in nearly two-thirds of the nontarget hosts to which it was fed. Such generalist species should not be recommende d for release, Infections comparable to those produced in L. dispar we re produced in 2% of the nontarget hosts fed Microsporidium sp. from P ortugal, 19% of nontarget hosts fed Microsporidium sp. from Romania, 1 3% fed spores of Microsporidium sp, from Slovakia, and 11% of nontarge t species fed N. lymantriae. The remaining nontarget species developed infections that, despite production of mature spores, were not typica l of infection in L. dispar. We believe it is very unlikely that these atypical infections would be horizontally transmitted within nontarge t insect populations in the United States. (C) 1997 Academic Press.