Selection of a strain of the granulosis virus of the codling moth with improved resistance against artificial ultraviolet radiation and sunlight

A six-step sequence of selection of the granulosis virus of Laspeyresia pomonella led to a strain with increased resistance to sunlight. Each step consisted of irradiation of dry deposits of the virus on apples with near range ultraviolet light, infection of freshly eclosed codling moth larvae with the irradiated virus, and propagation of the virus thus produced in large fifth-instar larvae. Compared with the original virus, the new strain was 5.6 times more resistant to artificial ultraviolet irradiation in the laboratory and remained twice as long infective in the field.