Postharvest Control Treatments for Hypothenemus obscurus (F.) (Coleoptera: Scolytidae) in Macadamia Nuts

Abstract

Postharvest control techniques, including controlled-atmosphere treatments, cold and heat treatments, and composting of infested macadamia husks and nuts, were evaluated for control of Hypothenemus obscurus (F.) in macadamia nuts. Exposure of infested nuts in-husk to ≥95% CO2 at ambient temperatures (24-30°C) for 6 d resulted in 97.3% (±2.1) mortality of adult beetles. All adult insects were killed at this exposure time and concentration when nuts were husked (nuts in-shell) before treatment. A 14-d treatment of ≥95% N2 was required for 100% mortality in unhusked nuts. A cold treatment of 7°C for at least 14 d was required to provide 100% adult H. obscurus mortality in nuts in-husk. A 7-d heat treatment at 45°C also provided 100% mortality. Composting infested, culled macadamia nuts and husks with urea in a wooden bin system resulted in 100% mortality in 14 d, whereas composting with poultry manure resulted in 100% mortality in 7 d. A more rapid mortality (7 d) was obtained in a closed (drum) composting system compared with an open system (windrow pile), in which 14 d were required for complete H. obscurus control.