DIFFERENTIAL LARVAL AGE SUSCEPTIBILITY OF THE MEDFLY, CERATITIS-CAPITATA WIED (DIPT, TEPHRITIDAE) TO CYROMAZINE

Ceratitis capitata Wied. larvae reared on an artificial diet supplemented with a range of concentrations of the IGI cyromazine, suffered severe developmental disruption depending on larval age. 100% mortality was recorded when young larvae (1- and 2-day-old) were exposed to a 10 mg/kg cyromazine-treated diet, whereas later-stage larvae (6- to 9-day old larvae; L6 to L9) were able to pupate with 25 to 100 mg/kg concentrations. Moreover the adult emergence rate was severely affected in these cases (less than 7 % for L6 to LS, and just 36% for L9). Larval mobility (measured as popped pupae) was drastically reduced except for L9. A significant larval growth inhibition at 3 days was observed in L2, L4 and L6, in a dependent dose manner: the median inhibitory concentration being near 1 mg/kg for young larvae, but reaching 100 mg/kg for the older ones.