Potential for hypobaric storage as a phytosanitary treatment: mortality of Rhagoletis pomonella (Diptera: Tephritidae) in apples and effects on fruit quality.

The efficacy of low-oxygen atmospheres using low pressure, referred to as hypobaric conditions, to kill egg and third-instar Rhagoletis pomonella (Walsh) in apples was investigated. Infested apples were exposed to 3.33 and 6.67 kPa in glass jars at 25 and 30 degrees C for times ranging from 3 to 120 h. Probit analyses and lethal dose ratio tests were performed to determine differences in lethal time values. Eggs were more tolerant of low pressure compared with third-instar R. pomonella. Mortality of eggs and larvae increased with increase in time of exposure to low pressure and temperature. Lower pressures increased percent mortality of eggs, but these values were not significantly different at the pressures tested in this investigation. The LT99 for R. pomonella eggs at 3.33 kPa was 105.98 and 51.46 h, respectively, at 25 and 30 degrees C, which was a significant effect of the higher temperature on egg mortality. Investigation into consumer acceptance of low-pressure-treated apples was done with 'Red Delicious' and 'Golden Delicious'. Apples exposed to 3.33 kPa at 25 and 30 degrees C for 3 and 5 d were stored at 1 degrees C for 2 wk and presented to a sensory panel for evaluation. The panelists rated treated apples with untreated controls for external and internal appearance and taste. Golden Delicious apples were unaffected for all three sensory factors across both temperatures and exposure times. Although taste was unaffected for Red Delicious, the internal and external appearances deteriorated. Use of low pressure for disinfestation and preservation of apples is a potential nonchemical alternative to chemical fumigants such as methyl bromide and phosphine.

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.

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.