New prospects for Ethyl formate as a fumigant for the date industry

Abstract

Date infestation of nitidulid beetles poses a serious contamination problem for which methyl bromide (MB) provided a solution. However, because of the phase out of MB, alternatives were investigated. Thermal disinfestation method has been successfully applied to some dry date varieties except to Deglet-Noor, Zahidi, and Ameri which are handled in crates of 200 kg to 400 kg. Therefore, thermal disinfestation was not successful because of delayed heating due to the resistance of the dates to hot airflow. The fumigant formulation Vapormate^TM was tested as alternative to MB for the disinfestation (proportion of insects found outside the feeding sites) and control of nitidulid beetles from artificial feeding sites at laboratory and for  dates in crates at semi-commercial conditions. Vapormate^TM contains 16.7% ethyl formate mixed with carbon dioxide. At laboratory conditions the effect of various dosages of VapormateTM was tested at 30^oC and at fixed exposure time of 12 h. Exposure of infested artificial feeding sies by larvae of Carpophilus spp. to the concentration of 280 g m^-3 of VapormateTM caused 69.3% disinfestation and 79.9% mortality, 350 g m^-3 resulted in 72.7% disinfestation and 98.8% of mortality and the optimal results were obtained at 420 g m^-3 that caused 69.6% disinfestations and 100% mortality. Commercial pilot-plant tests were carried out by applying 420 g m^-3 Vapormate^TM for 12 h in a 9 m³ flexible liner made of laminate composed of polypropylene/aluminum/polyethylene to cover crates containing infested dates. Disinfestation was tested on naturally infested dates that resulted in an average 100% disinfestation and 95% mortality, while with the artificially infested dates, disinfestation was 97% and mortality 96%. In a second series of tests, a commercial rigid fumigation chamber of 95.6 m³ was used. After 12 h exposure, 100% mortality was recorded in all date samples. Following the promising results, Vapormate^TM was registered in Israel for use by the date industry as an alternative to MB.

Keywords: Date, Nitidulid beetles, Ethyl formate, Vapormate^TM, Fumigation.