|Hansen, James D|
Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2000
Publication Date: 11/15/2000
Citation: Wang, S., Ikediala, J.N., Tang, J., Hansen, J.D., Mitcham, E., Mao, R., Swanson, B. 2000. Radio frequency treatments to control codling moth in in-shell walnuts. Postharvest Biology and Technology. 22:29-38. Interpretive Summary: The United States produces about two thirds of the world's walnuts. In-shell walnuts require repeated postharvest fumigations to control for insect pests, particularly codling moth, while in storage before export. However, environmental and health concerns are restricting the use of two major fumigants, phosphine and methyl bromide. Therefore, a practical alternative is needed for pest control, which has minimum impact on walnut quality. This manuscript describes the results of a new approach for postharvest disinfestation, the application of radio frequency. These treatments use electromagnetic energy to differentially heat the pest within the commodity, which effectively kills the pest. Yet, quality tests indicate no significant change to the walnut itself. Thus, a new efficacious method is being developed that will provide adequate phytosanitation for walnuts intended for export.
Technical Abstract: 'Diamond' walnuts (Juglans regia) in the shell were treated with radio frequency (RF) energy in a 27 MHz pilot-scale system to determine the treatment effect on third-instar codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), mortality and walnut quality. After 2 and 3 min of RF treatments, infested in- shell walnuts were heated to 43 and 53 deg C. The corresponding insect mortality reached 78.6 and 100%. The concentration of fatty acid (FA) of treated walnuts was not affected by RF treatments. The FA values were less than or equal to 0.1% after accelerated storage times up to 30 days at 35 deg C, simulating storage at 4 deg C for up to 3 years. The effect of RF treatments on walnut oil peroxide values (PV) was not significant. The PV value of walnuts was less than the 1.0 meq/kg (the upper limit for good quality walnuts), after 20 days storage at 35 deg C that simulated 2-year storage at 4 deg C. The PV value was about 1.2 meg/kg after 30-day storage at 35 deg C. RF treatments can, therefore, potentially provide an effective and rapid quarantine security protocol against codling moth in walnuts as an alternative to methyl bromide fumigation.