POSTHARVEST CONTROL TREATMENTS FOR HYPOTHENEMUS-OBSCURUS (F) (COLEOPTERA, SCOLYTIDAE) IN MACADAMIA NUTS

Postharvest control techniques, including controlled-atmosphere treatm ents, cold and heat treatments, and composting of infested macadamia h usks and nuts, were evaluated for control of Hypothenemus obscurus (F. ) in macadamia nuts. Exposure of infested nuts in-husk to greater-than -or-equal-to 95% CO2 at ambient temperatures (24-30-degrees-C) for 6 d resulted in 97.3% (+/-2.1) mortality of adult beetles. All adult inse cts were killed at this exposure time and concentration when nuts were husked (nuts in-shell) before treatment. A 14-d treatment of greater- than-or-equal-to 95% N2 was required for 100% mortality in unhusked nu ts. A cold treatment of 7-degrees-C for at least 14 d was required to provide 100% adult H. obscurus mortality in nuts in-husk. A 7-d heat t reatment at 45-degrees-C also provided 100% mortality. Composting infe sted, culled macadamia nuts and husks with urea in a wooden bin system resulted in 100% mortality in 14 d, whereas composting with poultry m anure resulted in 100% mortality in 7 d. A more rapid mortality (7 d) was obtained in a closed (drum) composting system compared with an ope n system (windrow pile), in which 14 d were required for complete H. o bscurus control.