Allomones and other repellents for pest management of the storage mite Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae)

Methyl bromide (MB) was the most effective fumigant used for stored products, but it is now banned for most uses as an ozone-depleting substance. Effective alternatives to MB are needed to develop integrated pest management (IPM) programs for the ham mite Tyrophagous putrescentiae. This study evaluated plant essential oils and synthetic food-safe compounds as repellents to protect dry-cured hams from mite infestation. Laboratory experiments to assess repellency to orientation and population growth of mites on pieces of aged country hams were conducted. Test compounds at different concentrations were assayed for mite orientation, and showed that C8910, a mixture of three short-chain fatty acids, and the sesquiterpene ketone nootkatone had repellency indices of (RI) of 85.6% and 82.3%, respectively, at a concentration of 0.1mg/cm², when applied to a Petri dish arena. DEET and icaridin were also tested but performed poorly with RI below 70 % even at 0.1 mg/cm² .The monoterpene alcohol geraniol had the highest RI of 96.3 % at 0.04 mg/cm². Ham pieces dipped in different concentrations of test compounds and then inoculated with 20 adult mites showed a significant and dramatic decrease in mite population growth compared to untreated pieces after 14 days. Our experiments suggest that some plant secondary metabolites and synthetic food-safe compounds could serve as methyl bromide alternatives for managing ham mites.