PULLMAN, Wash. – Radio waves, not environmentally damaging chemicals, may be the new, best, post-harvest process for debugging dried fruits and nuts, according to a team of researchers led by Washington State University professor Juming Tang.
Using radio waves that generate heat to kill the insects hiding in nuts and dried fruits provides a good alterative to methyl bromide, the most common form of post-harvest pest control, according to Tang, a scientist in WSU’s Agricultural Research Center and a fellow in WSU’s IMPACT center. Use of that chemical fumigant, which has been linked to ozone depletion, was banned in developed countries, including the United States, at the end of 2005, although temporary exemptions have been granted for some uses. Developing countries have until 2015 to end methyl bromide treatments.
The USDA Agricultural Research Service considers research on finding methyl bromide alternatives “one of its highest priorities.”
An intensive five-year laboratory study and a three-month pilot trial in a commercial walnut processing plant have shown convincingly that radio frequency treatments can effectively control post-harvest insect pests in in-shell walnuts without reducing product quality. Tang led a team of scientists that included presentatives from WSU (Shaojin Wang), University of California, Davis (Elizabeth J. Mitcham and Maria E. Monzon), and the USDA-ARS Parlier Station (Judy Johnson). The results of the scaling-up study are published in two papers in the latest issue of Postharvest Biology and Technology (2007, volume 45: 240-246, 247-253), a leading scientific journal in post-harvest research.
The research team has studied the heat response of several key post-harvest insects, and has developed suitable treatment protocols using radio frequency. “The same technology also may be extended to other commodities that require post-harvest pest control when they are shipped to other markets, such as lentils to India,” said Tang.
The research on walnuts is only a part of the team’s research. Engineers, entomologists and plant physiologists from Washington, California, Texas, Hawaii, Israel and the United Kingdom are exploring radio frequency energy as a method to control insect pests in a variety of products including tree fruits, nuts and legumes. This multi-institution and multi-disciplinary research was initiated with seed a grant from the WSU IMPACT Center, and supported by the California Walnut Market Board, U.S.-Israel Binational Agricultural Research and Development Program, USDA’s Initiative for Future Agriculture and Food Systems, the Natural Resources Initiative and the Cooperative State Research, Education, and Extension Service.
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