Susceptibility of Tribolium castaneum Life Stages Exposed to Elevated Temperatures during Heat Treatments of a Pilot Flour Mill: Influence of Sanitation, Temperatures Attained Among Mills Floors, and Costs

Abstract

The influence of sanitation on responses of life stages of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), was investigated in a pilot flour mill subjected to three, 24-h heat treatments by using forced-air gas heaters fueled by propane. Two sanitation levels, dusting of wheat flour and 2-cm-deep flour, were created in 25 plastic bioassay boxes, each holding eggs, young larvae, old larvae, pupae, and adults of T. castaneum plus two temperature sensors. Data loggers (48) were placed on the five mill floors to record air temperatures. The time required to reach 50 degrees C, time above 50 degrees C, and the maximum temperature among mill floors and in bioassay boxes were measured. The maximum temperature in bioassay boxes and in the mill was lower on the first floor than on other floors. This trend was apparent in time required to reach 50 degrees C and time above 50 degrees C, especially in compartments with 2-cm-deep flour. The mean +/- SE mortality of T. castaneum life stages on the first floor was 55.5 +/- 12.9-98.6 +/- 0.8%; it was 93.2 +/- 6.7-100 +/- 0.0% on other floors. Adults were the least susceptible stage. Mortality of T. castaneum stages in compartments with 2-cm-deep flour was generally lower than those with flour dust. Costs for the three heat treatments ranged from US$27,438 to $28,838. An effective heat treatment can be conducted within 24 h, provided temperatures on mill floors reach 50 degrees C in 8-12 h and are held above 50 degrees C for at least 10-14 h, with maximum temperatures held between 50 and 60 degrees C.

Impact of radiofrequency disinfestation on Tribolium castaneum (Herbst) in wheat flour and its influence on the functional characteristics of wheat flour

“…During RF heating, mortality differences among life stages of T. castaneum were significant in E2 treatment (p < .05). In E3 treatment all life stages were found to be killed and the difference was not significant at p < .05 (Brijwani et al, 2012) which implies that 0.9 A current load with 15 min exposure time results in 100% disinfestation.…”

Greenhouse test of spraying dsRNA to control the western flower thrips, Frankliniella occidentalis, infesting hot peppers

“…The non-target insects included Thrips tabaci , Plutella xylostella , Tenebrio molitor , and Tribolium castanum . These test insects were obtained from laboratory cultures of T. tabaci [ 19 ], P. xylostella [ 18 ], T. molitor [ 20 ], and T. castaneum [ 21 ]. The larval stages of these species were used for the bioassays.…”

Dispersion, efficacy, and persistence of dichlorvos aerosol against two flour beetle life stages in a mill

“…After 2 d at 28 C and 65% r.h., the flour was sifted through an 841-mm opening sieve to remove adults. The flour with eggs in containers was held at the rearing conditions for 24 d before sifting the flour through a 250-mm sieve to collect pupae (Brijwani et al, 2012).…”

“…The layout of the mill has been described in detail by Brijwani et al (2012). The airhandling system was shut down during the aerosol treatment.…”