http://www.eurekalert.org/pub_releases/2016-04/uoia-ssc033016.php
Their study, reported in the Proceedings of the National Academy of Sciences, found that N. bombi was present in the U.S. as early as 1980, well before several species of wild bumble bees started to go missing across the country. The study also found that N. bombi infections in large-scale commercial bumble bee pollination operations coincided with infections and declines in wild bumble bees