Replacing Ozone-Depleting Pesticides: Methyl Bromide Alternatives to Control Mold Mites

Tyrophagus putrescentiae(Schrank), also known as the mold mite, is a cosmopolitan pest species that infests stored food products with high fat and protein contents, including dry-cured ham. Methyl bromide (MeBr) is a broad spectrum fumigant that can eliminate a wide range of pest species. Several dry cured ham plants in the U.S. use MeBr to control mold mite. However, methyl bromide is classified as an ozone depletion substance and will be phased out in the near future. Therefore, there is a significant need to find an economical and effective alternative compound and method to control mite infestations. Various types of food additives have indicated high efficacy on mortality or fecundity of stored product mites. First part of studies were done to evaluate a simple method for coating hams with food-safe compounds to effectively suppress mold mite populations. Sulfuryl fluride (SF) is a broad spectrum fumigant. Studies showed SF killed all life stages of mold mites but the eggs. Extreme temperature has been known as a management tool to control insect and mite pests. Second part of studies were done for evaluation of effectiveness of SF combined with heat on mortality of mold mites. Method: Food additives bioassay: Cubes of dry cured ham treated with different concentrations of low risk materials, by dipping the cubes in the solution. Salts of sorbic, and citric acids, short-chain “polyols”, animal and plant oils, and butyl ester preservatives were examined. Twenty randomly selected adult mites were placed on each treated ham cube. The number of adults and nymphs after 2 weeks of incubation were determined. Combination of SF and heat bioassay: Variation in fumigant exposure time, temperature and fumigant concentration was evaluated. 20 unsexed adult and nymph mites and 10 eggs were transferred to 4 ml ventilated vials. Replications were exposed for different time periods ranging from 12 to 48 hrs. and variable SF concentrations at 25, 30, 35, and 40°C. Results: Results indicated that Ethoxyquin and calcium sorbate at the highest concentration, and propylene glycol and lard at the concentration of 50% significantly reduced the population growth of mites. At the highest concentration of butylated hydroxytoluene, no survival was observed after 2 weeks. At the temperature of 40°C, all adults and nymphs died after 12 hrs, while eggs were controlled after 36 hrs at SF concentrations of 1400 (oz.-hr). After 48 hrs. exposure time, the temperature of 35°C caused 100% mortality in adults and nymphs, however there was 100% mortality of eggs at 40°C with the same amount of SF. When mite eggs were exposed to different SF concentrations for 36 hrs. at 36 °C, 92% mortality was measured at 1440 (oz.-hr). Conclusion: Results revealed that examined food additives were effective at controlling mite infestations and mite population suppression increased by applying higher concentrations of these food additives to cubes of ham. This study also suggests that combining SF with heat may be an effective methyl bromide alternative to control the mold mite.