Evaluation of Low Pressure and Vapor Heat as a Phytosanitary Treatment For Chlorophorus annularis (Coleoptera: Cerambycidae) in Postharvest Bamboo Poles.

The bamboo longhorned beetle, Chlorophorus annularis (Fabricius), distributed widely in Asian countries attacking live or postharvest bamboo, is a concern to the international trade of bamboo materials. With the phase out of methyl bromide for quarantine and preshipment use, a reliable, safe, and environmentally friendly phytosanitary treatment is needed as an alternative. In this study, the thermotolerance of C. annularis larvae at atmospheric pressure was examined. The results showed that the thermotolerance increased with instar. The fifth instar was the most thermotolerant stage at 48 and 50°C. A series of vapor heat treatment tests were conducted for bamboo poles infested with C. annularis at the vacuum levels of 15, 30, 50, 70, 90, and 100 kPa at the temperatures of 40, 44, 48, 52, and 56°C with a holding duration of 15 min. The lower pressure or higher temperature increased the mortality of C. annularis. In total 473 larvae were treated at 48°C and 50 kPa for 15 min. Only one larva was found alive, resulting in a mortality rate of 99.7886%. In total 418 larvae were treated at 52°C and 100 kPa for 15 min resulting in 100% mortality. Based on these two results, a heat treatment of 52°C for 15 min at 50 kPa can be used as a low pressure vapor heat treatment for bamboo articles infested with C. annularis. The vapor heat treatment combined with low pressure is an effective alternative phytosanitary measure for bamboo articles.