Disinfestation efficacy of almond pasteurization processes to control Indian meal moth and red flour beetle

Pasterurization using chemical or thermal treatmes ensuring microbial safety of almonds to achieve a minimum 4-log reduction of Salmonella is mandatory practice for California almond growers. However, recent complaints about infestatiation of the pasterurized product by stored product pests, Indian meal moth and red flour beetle, initiated this study to evaluate the disinfestation efficacies of commonly used pasterurization process. We evaluated three industry approved almond pasterurization processes, i.e., steam under vacuum, in-line steam, and propylene oxide fumigation, and phosphine fumigation to control all life stages of red flour beetle and Indian meal moth. Young eggs (72-h-old), young larvae (1^st and 2^nd instars), old larvae (3^rd and 4^th instars), pupae, adults were tested. Additionally, infested almonds consisting of multiple life stages simulating the real-world infestation was also evalutated. Insect specimens contained in fabricated nylon mesh cages were exposed to treatments in commercial treatment facilities. All treatments effectively controlled all life stages of both species despite their location inside the treatment chambers. Steam under vacuum, in-line steam, propylene oxide fumigation, and phosphine fumigation resulted in zero survivors out of the 150-300 of each life stage of both species in each of three replications. Complete control of all life stages of both species indicates that any infestation of the pasterurized product is probably a result of re-infestation.