Fumigant toxicity and persistence of Eucalyptus camaldulensis and Callistemon viminalis essential oils on Oryzaephilus surinamensis and its ectoparasitoid Cephalonomia tarsalis

Fumigant toxicity of Eucalyptus camaldulensis (Dehnh) and Callistemon viminalis (Gaertn) essential oils was investigated against adults (1-3 days old) of Oryzaephilus surinamensis L. and Cephalonomia tarsalis (Ashmead). The essential oils were obtained by the hydrodistillation method, using a modified Clevenger apparatus. The experiments were carried out at 27± 1 °C and 65 ±5% R.H. in a dark condition. Results of fumigant toxicity tests showed that mortality was increased with the increase in concentration and time. The lethal concentration of E. camaldulnsis and C. viminalis to cause 50% mortality of O. surinamensis (LC50) was estimated to be 3.27 and 1.42 µL/L air and for C. tarsalis LC50 values were 0.52 and 0.72 µL/L air, respectively which indicated more susceptibility of C. tarsalis compared to O. surinamensis. The lethal time to kill 50% of the adults (LT50) at concentrations of 35.71, 32.14, 28.57 and 25 µL/L air lasted 5.84, 5.59, 5.34 and 4.94 h for E. camaldulnsis oil and 4.33, 3.93, 3.61and 2.09 h for C. viminalis, respectively. The persistence of essential oils of E. camaldulensis and C. viminalis at 35.71 µL/L air against O. surinamensis was 11 and 6 days, and for C. tarsalis, the oil persistence reached 56 and 20 days, respectively.