Hawaiian Fruit Flies (Diptera: Tephritidae): Toxicity of Benzyl Isothiocyanate against Eggs or 1st Instars of Three Species1

Abstract

The natural mortality of the eggs and 1st instars of Dacus dorsalis Hendel, Ceratitis capitata (Wiedemann), and D. cucurbitae Coquillett, in green papaya, Carica papaya L., was partly due to the toxicity of benzyl isothiocyanatc (BITC) which was produced naturally when the tissues were physically damaged during oviposition and larval feeding. The order of increasing susceptibility of the insects to BITC was 1st instars and then egg, and with respect to species, D. dorsalis, C. capitata , and D. cucurbitae . A BITC concentration of 847.0 ppm in artificial latex eliminated 50.0 or 99.9% of D. dorsalis eggs in 10.4 or 37.0 min, respectively, at 25°C. About 140.0 ppm produced similar effects with C. capitata , but D. cucurbitae did not survive at concentrations more than 9.3 ppm. Also, BITC enriched papaya puree prevented hatch of D. dorsalis eggs by 50.0 and 99.0% at 20.4 and 43.5 ppm, respectively. The mortality of the 1st instars was similarly affected at 19.3 and 33.8 ppm. C. capitata eggs required 9.3 and 24.0 ppm, but the larvae did not survive at either concentration. The BITC concentration produced by mature-green or color-turning papaya was more than 52 ppm, which was sufficient to prevent the development of an infestation after partial deterrence of oviposition.