Efficacy of the Fumigants Propylene Oxide and Ethyl Formate to Control Two Pest Species of Dry-Cured Hams

SIMPLE SUMMARY: The ham mite Tyrophagus putrescentiae and the red-legged ham beetle Necrobia rufipes are pests of dry-cured country hams that are aged for up to two years. These pests had been effectively controlled by the fumigant gas methyl bromide, which is now banned from all uses on postharvest foods except for quarantine applications. The alternative fumigants propylene oxide and ethyl formate can control several stored-product pest species but have not been studied for these ham pests. Here, we have evaluated propylene oxide and ethyl formate for controlling the ham mite and the red-legged ham beetle. Laboratory experiments of each fumigant applied to mixed life stage populations of both pests confirmed that they could be controlled at reasonable gas concentrations either with or without the presence of dry-cured ham, dog food kibbles, or fish meal in small fumigation chambers. Mite eggs were the most difficult to control. Both fumigants were effective at suppressing the mites and red-legged ham beetles at appropriate gas concentrations. While there were no negative effects of any gas being released from treated foods after fumigants were vented, these effects from the presence of commodities requires additional research. Overall, the use of propylene oxide or ethyl formate to control pests on dry-cured hams during the aging process is potentially feasible and should be studied further. ABSTRACT: The ham mite Tyrophagus putrescentiae and the red-legged ham beetle Necrobia rufipes are harmful pests to several high-valued stored products. The regulatory phase-out of the fumigant methyl bromide necessitates the search for alternative fumigants. Propylene oxide (PPO) and ethyl formate (EF) were therefore evaluated in the laboratory for controlling these pests of dry-cured hams. Concentration–mortality studies at 25 °C of PPO and EF found that the mobile stages of the mites were very susceptible to low concentrations of 10 mg/L and less of each gas, while mite eggs were very tolerant and required 20 mg/L for PPO and 80 mg/L of EF for 100% mortality. Mixed life stage cultures of mites and beetles were treated for 24 h with either PPO or EF at 1× and 2× the estimated 99% lethal doses and confirmed effectiveness for controlling simulated pest populations. The sorptive properties of each gas in chambers with ham pieces, dog food kibbles, or fish meal were minimal for a reduction in mite toxicity when compared to treatments in empty chambers. There was no evidence that any desorbed gas occurred at a level toxic to mite eggs in any of the fumigated commodities. These fumigation studies with ham pests support further work with PPO and EF on any changes in the sensory quality of dry-cured hams for human taste and for commercial-scale fumigations toward regulatory approval.