Temperature and (or) crowding (larval density) functioned as stressors in the induction of symptoms associated with the nucleopolyhedrosis virus of the European pine sawfly, Neodiprion sertifer, Subsamptes of larvae maintained at 30 and 35°C, with three levels of larval density each (20, 60, and 100/shoot) which had died under these conditions, revealed the presence of polyhedral inclusion bodies under microscopic examination. In contrast, larvae maintained at 25°C with the same three larval density levels experienced no symptoms of virus infection or mortality, The latter was consistent with field observations when temperatures during larval development ranged from 14°C to 27°C and larval densities were in the same general range.
Mohamed, M. A.; Coppel, H. C.; and Podgwaite, J. D.
"Temperature and Crowding Effects on Virus Manifestation in Neodiprion Sertifer (Hymenoptera: Diprionidae) Larvae,"
The Great Lakes Entomologist, vol 18
Available at: https://scholar.valpo.edu/tgle/vol18/iss3/4