Hawaiian Fruit Flies (Diptera: Tephritidae): Variation of Index of Infestation with Benzyl Isothiocyanate Concentration and Color of Maturing Papaya1

The natural tendency to oviposit by Dacus dorsalis Hendel, Ceratitis capitata (Wiedemann), and D. cucurbitae Coquilleu, was deterred by benzyl isothiocyanate(BITC) at concentrations of 6.7 × 10-4 mole/kg of agar medium or 1.9 × 10-10 mole/liter of air above the medium in ovipositional devices. The result was a mean percent reduction to 57.7, 93.3, and 93.6% of the control at 1.9 × 10-10 mole/liter by the three species, respectively, and to more than 99% at higher BITC concentrations. For a similar effect with ripe papayas, a 10-fold increase of BITC concentration above 1.9 × 10-10 mole/liter would be required, possibly, due to the presence of masking volatile compounds. Thus, the mean index of D. dorsalis infestation (number of larvae per fruit) of papaya, Carica papaya L., varied directly with ripeness expressed as a volume determined from absolute colorimeter readings of L, a, and b, which was 0.92 for color-turning papayas, at an index of zero.