Susceptibilities of Five Species of Scales (Diaspididae and Coccidae) and Mealybugs (Pseudococcidae) to Fumigation with a Gas Mixture of Ethyl Formate and Carbon Dioxide under Normal Atmospheric Pressure or Vacuum

摘要

Five species of scales (Diaspis boisduvalii, Aonidiella auranti, and Coccus hesperidum) and mealybugs (Planococcus citri and Dysimicoccus brevipes) were fumigated with a gas mixture of ethyl formate (EF， C3H6O3) and carbon dioxide (CO_2) to simulatea fumigation by using a commercial product formulation (EF16.7% + CO2 83.3%, w/w) and their susceptibilities were investigated. All developmental stages of D. boisduvalii, A. auranti, and C, hesperidum tested were completely killed at a fumigation dosageof EF 25.1 mg/1+ CO2124.9 mg/1 (equivalent to150 mg/1 of the gas mixture) for 3 h at 15^3. Crawler, nymph, and adult D. brevipes were more tolerant than P. citri: however, these stages of both mealybugs were 100% killed at dosages of EF 16.7 mg/1+ CO_2833 mg/1 (100 mg/1 of gas mixture) for 3 h at 1513. Among the five species tested, the least susceptible stage was P. citri eggs, which showed 25.3%, 54.2%, and 92.3% mortality at gas mixture dosages of150 mg/L 250 mg/1 (EF 41.8 mg/1+ CO_2 208.3 mg/1), and 350 mg/1 (EF 58.5 mg/1+ CO_2 291.5 mg/1),respectively. LD50 and LD95 for the P. citri egg stage under gas mixture fumigation were calculated as 242.0 mg/1 and 408.0 mg/1. The efficacy of gas mixture fumigation was increased under vacuum [く18-22 kPa (ABS)]. Mortalities of P. citri egg were increased under vacuum of up to 61.2%, 70.2%, and 100% with a gas mixture at150 mg/1,250 mg/1, and 350 mg/1 dosage rates, respectively.