Four methods for propagation of Granulovirus phthorimaea on Phthorimaea operculella (Zeller) larvae were evaluated under laboratory conditions. The methods were: immersion of potato, Solanum tuberosum L., tuber; application by cotton swab to larvae; larval immersion and aspersion with viral suspension (homogenized water with one to 15 infected larvae). The objectives were to develop a method adapted to in vivo production of the virus and to determine susceptibility of P. operculella to the virus. Larval immersion was significant at 5, 10, and 15 days after evaluation, killing 55.0, 77.5, and 87.5%, respectively, of second and third instars. LC₅₀ was estimated based on the number of first-instar larvae per liter of water (0, 1, 3, 6, 9, 12, and 15). LCs were 7.8, 3.7, and 2.0 larvae per liter of water at 2, 5, and 8 days, respectively, and varied according to the time data were collected.