Adult boll weevils,Anthonomous grandis, fed for 4 days from emergence on a dyeimpregnated artificial diet before illumination at 3800μW/cm2fluorescent light for 4 h yielded a dietary LD50value of 9.9×10−4moles/liter and a tissue LD50value of 2.4×−7moles/g wet weight for rose bengal. The dye-sensitized photooxidation reaction was treated mathematically and 2nd order rate constants of 4.50 liters/mole·min for dietary rose bengal and 2.25×104g/mole·min for tissue rose bengal were calculated.