|Hansen, James D|
Submitted to: Acta Horticulture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2005
Publication Date: 5/15/2005
Citation: Mitcham, E., Monzon, M.E., Simpson, T., Bikoba, V., Biasi, W.V., Feng, X., Hansen, J.D., Tang, J., Wang, S., Johnson, J.A. 2005. Radio frequency heating of walnuts and sweet cherries to control insects after harvest. Acta Hort. 682:2133-2139. Interpretive Summary: Insect pests in fresh commodities often become a problem with international commerce. Yet, environmental and health concerns are restricting the use of conventional methods of control, such as fumigation. Researchers from the USDA-ARS laboratories, along with their collaborators at the University of California at Davis and Washington State University, examined radio frequency heating of walnuts and sweet cherries to determine efficacy and applicability of pest control. The treatments were successful against larvae of the navel orangeworm infesting walnuts without affect commodity quality. However, cherry fruits were damaged at levels needed to control larvae of the codling moth, and the radio frequency heating treatment did not appear promising.
Technical Abstract: Radio frequency (RF) heating has been explored as a potential non-chemical method to control insects in harvested walnuts and as a quarantine treatment for ‘Bing’ sweet cherries. Walnuts were heated to 50 to 90°C. Heating walnuts to 55°C or higher resulted in 100% mortality of fifth instar navel orangeworm, and heating to 80°C had no effect on walnut quality. Moisture content had a significant influence on the heating rate of the walnut kernels. For industrial applications, walnuts could move on a conveyor through one or more RF systems with mixing of nuts between systems. ‘Bing’ sweet cherries were heated in a polyethylene container holding 10 liters of circulating distilled water with 2.3 g of NaCl. Fresh fruit must be treated in a saline solution to prevent burning at fruit contact points, and circulation improves heating uniformity within the RF field. Cherries were equilibrated in 38°C water for 6 minutes, then heated with RF energy to target temperatures between 50 and 54.5°C and held for 0.5 to 6 min before hydrocooling. Fruit were stored for 1 day at 5°C or 14 days at 0°C to simulate air or sea shipment, respectively. Shorter treatments at higher temperatures were better tolerated than longer treatments at lower temperatures. Cherry fruit infested with codling moth larvae were subjected to the same treatments. Mortality was 100% in all treatments except those at 50°C. However, fruit quality was unacceptable following sea shipment and marginal following air shipment. Treatment times would be significantly longer to provide for Probit 9 security (99.968%) required for export to Japan and therefore RF treatments do not appear promising for sweet cherry fruit.