Orientation and oviposition preference of the stored-product mite, Tyrophagus putrescentiae (Shrank), for HAM with various treatments

Methyl bromide (MB) use is currently the only effective method used to control Tyrophagus putrescentiae (Shrank) (Acari: Acaridae), a major mite pest of cured ham, cheeses and other high value foods. MB is being banned as an ozone-depletor so alternative methods must be developed. Commonly used food preservatives such as glycerol, propylene glycol, propionic acid, calcium propionate and sodium sorbate were tested for their efficacy in preventing mite infestation. Two-choice orientation and oviposition tests comprising one treated and one untreated (control) ham cubes were set up in arenas in total darkness at 27±1 °C and 70% RH. Propylene glycol and glycerol were tested at 25%, 50%, 75%, and 100% and propionic acid, calcium propionate and sodium sorbate at 1%, 5%, and 10%. Cubes were dipped in the various concentrations (treatments) or in water (controls) for one minute and then air-dried for two hours. Untreated cubes were also compared with artificial mite diet. Twenty adult mites were introduced per assay. All treatments were significantly different from the control (P < 0.05); exhibiting Response Index (percentage of mites on treated hams after two hours) values significantly less than 50. Fewer eggs were laid on the treated hams after 48 hours. Also, more mites oriented to and oviposited on the artificial diet hence its use as food bait in a trap being developed. In most treatments, the lowest and highest concentrations provided similar levels of protection of the hams. Therefore, the lowest concentrations may help reduce mite infestation in future applications.