Don T. Canerday

The effect of heat, buffer salt and H-ion concentration, and ultraviolet light on the infectivity of Heliothis and Trichoplusia nuclear-polyhedrosis viruses

Abstract The thermal inactivation point of Heliothis nuclear-polyhedrosis virus (HPV) was determined to be between 75° and 80°C for 10 min; that of the Trichoplusia nuclear-polyhedrosis virus (TPV) was between 82° and 88°C. Infectivity of HPV was reduced when the virus was buffered at pH 2 or 12 for 30 min to 24 hr but was unaffected at pH 5, 7, or 9. The concentration of phosphate buffer used appeared to have little effect. TPV polyhedra dissolved after 30 min in 0.1 m phosphate at pH 11, but infectivity was not lost until a pH of 12 was reached. HPV was inactivated by ultraviolet light after 5 min at 2 inches from the light source. Infectivity of TPV was greatly reduced by exposures of 4–10 min to ultraviolet at 2 inches; total inactivation did not occur after 60 min, but did after 120 min. Effect of ultraviolet on both viruses was progressively lessened as distance from light source to virus increased. No reduction in infectivity of either virus occurred at an exposure distance of 32 inches.