Use of Ethyl Formate Fumigation to Control Adult Bean Thrips in Navel Oranges

Shipments of California Navel oranges (Citrus sinensis) (Osbeck)) that are found to be infested with adult bean thrips (Caliothrips fasciatus (Pergande) (Thysanoptera: Thripidae)) upon arrival in Australia either undergo mandatory fumigation with methyl bromide (MeBr) to kill the thrips or are refused entry. Ethyl formate (EtF) mixed with carbon dioxide (CO₂) is an effective fumigant for control of various arthropods including but not limited to, thrips, aphids, Pacific spider mites, California red scale, and omnivorous leaf rollers. Dose-mortality curves at 5°C, 10°C, and 15°C were developed for control of adult bean thrips using EtF plus CO₂, with 5°C being more effective. In further testing, the efficacy of EtF plus CO₂ against adult bean thrips in Navel oranges and the impact on fruit quality after fumigation followed by 5 wk of storage at 5°C and shelf life at 20°C was determined. Fruit fumigated with 31 g/m3 EtF plus CO₂ at 5°C for 1 h showed no difference in quality compared with untreated control fruit. Ethyl formate plus CO₂ fumigation efficacy was confirmed in a 27.32 m3 sea freight container with eight pallets of packed Navel oranges (load factor 28.69%) and 10,000-15,000 adult bean thrips in each of three replications. Complete control of adult bean thrips was achieved with no negative effects on fruit quality.