Efficacy of propylene oxide and ethyl formate as fumigants to control Lasioderma serricorne (F.) (Coleoptera: Ptinidae)

Abstract

Propylene oxide (PPO) and ethyl formate (EF) can be applied in the gas phase as fumigants for stored product pests. PPO and EF are effective against several insect species, but thorough studies on Lasioderma serricorne, the cigarette beetle, are lacking. Here we evaluated the toxicity of PPO and EF to control different life stages of L. serricorne under laboratory conditions at 25 °C, and we studied sorption of these gases on three commodities. Lasioderma serricorne larvae were the most tolerant to PPO with an LC50 of 41.08 mg/L, while pupae were the most tolerant to EF with an LC50 of 28.14 mg/L. Tolerant life stages were controlled in 3 h using 70.09 mg/L PPO or by using 95.22 mg/L of EF. Validation studies over a six-week period with mixed life stage colonies using 100 mg/L of either fumigant resulted in 100% control of all life stages. Beetle mortality in the presence of dried leaf tobacco was reduced by 80% and 40% during 12 h and 24 h exposure to PPO, respectively. While there was no reduced mortality related to sorption by commodities during a 12 h exposure to EF, we observed a very small reduction of mortality in jars with tobacco during a 24 h exposure. Desorption of EF from pet food after ventilation caused 20% mortality of L. serricorne pupae during a 12 h exposure, while flour and tobacco had no significant desorption mortality from EF. No tangible desorption effects were found for any commodity following fumigation with PPO. These studies showed that fumigation with PPO and EF for 24 h can control the most tolerant life stages of L. serricorne at 25 °C. Future work should investigate commercial scale fumigations of cigarette beetles with commodities under a variety of physical conditions.