Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/29/2013
Publication Date: 5/1/2013
Citation: Hulasare, R., Payton, M.E., Hallman, G.J., Phillips, T.W. 2013. Potential for hypobaric storage as a phytosanitary treatment: Mortality of Rhagoletis pomonella (Diptera: Tephritidae) in apples and effects on fruit quality. Journal of Economic Entomology. 106(3):1173-1178. DOI: http://dx.doi.org/10.1603/EC12343. Interpretive Summary: Storage under low oxygen conditions increases the shelf life of fresh fruits and vegetables and is being used increasingly for that purpose on a commercial basis. It is known experimentally to kill insects as well and has been researched as a treatment to kill insects that may be present in fruit exported to areas where those insects do not exist and might become established. However, that application is not used commercially. Low pressure is a way of achieving low oxygen storage. Although it has been researched considerably for use against stored-product insects, little research has been done for control of quarantine pests of significance on fresh fruits and vegetables and no research that we are aware of has been done for control of an internal feeder in a fruit, which are the most important and difficult to manage quarantine pests. This research investigated low pressure to kill eggs and larvae of the apple maggot (Rhagoletis pomonella) in apples. Infested apples were exposed to two pressures, 3.33 and 6.67 kPa (kilopascals) (0.5 to 1 pound per square inch), in jars at 25 and 30°C (77 and 86°F) for 3-120 hours. Mortality of eggs and larvae increased with increase in time of exposure. Apples exposed to 3.33 kPa at 25 and 30°C for 3 and 5 d were unaffected for aroma and taste, although in ‘Red Delicious’ but not ‘Golden Delicious’ apples the internal and external appearances were affected. Eggs and larvae were all killed at conditions that did not affect ‘Golden Delicious’. Use of low pressure for disinfestation and preservation of apples is a potential, non-chemical treatment for exported fruit.
Technical Abstract: The efficacy of low-oxygen atmospheres using low pressure, referred to as hypobaric conditions, to kill egg and 3rd 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°C for 3-120 h. Probit analyses and lethal-dose ratio tests were performed to determine differences in lethal time (LT) values. Eggs were more tolerant of low pressure compared to 3rd instar R. pomonella. Mortality of eggs and larvae increased with increase in time of exposure to low pressure and temperature. Lower pressures increased percentage 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 105.98h and 51.46 h at 25 and 30°C, respectively, 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’ cultivars. Apples exposed to 3.33 kPa at 25 and 30°C for 3 and 5 d were stored at 1°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’ cultivar, the internal and external appearances deteriorated. Use of low pressure for disinfestation and preservation of apples is a potential, non-chemical alternative to chemical fumigants such as methyl bromide.