Cadavers of larvae killed by the gypsy moth fungus and virus can be roughly differentiated in the field. There is considerable variability in cadaver symptoms so microscopic examination is necessary for more precise determination of the cause of death. Photographs in figures 1 and 2 by Donald R. Specker, Drawing in figure 3 and graphic design by Tana L. Ebaugh. Individual cadavers can contain both fungal and viral structures.
Fungal spores are usually about ten times larger than viral structures.
Resting spores within late instars remain identifiable for prolonged periods with no special treatment of the cadavers. Resting spores are rarely produced in early instars. To observe cadavers contents, cadavers should be soaked in water, a small section excised and placed on a microscope slide in a drop of water, and covered with a slip. Dissected material can then be easily observed at 100 - 400x on a compound microscope. If phase contrast is available on your microscope, this provides an additional diagnostic tool for identification of the virus.