Pressure treatment may replace fumigation
Synopsis: A Washington State University study is looking at low-pressure treatment to replace chemical fumigation to make sure apples and cherries are bug free before they are exported.
   Replacing chemical fumigation of apples and cherries for export with low-pressure treatment is the focus of a new study by a Washington State University assistant research professor.
   Professor Shaojin Wang is looking at a method of postharvest pest control that he says has worked with mangoes and nuts.
  The LP system to be used in this project works by maintaining product in a 10 to 15 mm Hg (1.3 to 2.0 kPa) vacuum regime with controlled airflow providing 0.02 to 0.10% oxygen (depending on temperature), 0% carbon dioxide, no ethylene, and nearly 100% relative humidity at optimal constant temperatures, Wang said.  Under these conditions, insect pest could be controlled and fruit quality could be maintained, he said
   On Oct. 1, Wang began a two-year study funded by a grant from the USDA’s National Institute of Food and Agriculture. Co-investigators are Tom Davenport, a horticulturalist at the University of Florida, and Judy Johnson, a USDA-ARS entomologist in Parlier, Calif. The project is also supported by Atlas Technologies, a low-pressure equipment company in Port Townsend, Wash.
   Chemical fumigation of apples and cherries before they are exported is being phased out by international agreements over concern of harm to human health and the environment, especially the ozone layer, Wang said.
   For more than a decade, he has studied radio-frequency technology as an alternative which has worked with dry products such as nuts and legumes but hasn’t worked well with fresh fruits because of their heat sensitivity, he said.
   Jim McFerson, manager of the Washington Tree Fruit Research Commission in Wenatchee, said the radio-frequency technology often has been detrimental to fruit quality and hasn’t been affordable.
   Methyl bromide as a fumigant is safe when used properly but too long a treatment can ruin cherries, McFerson said.
   “We’ve looked at various approaches to control pests and diseases in tree fruit and supported such work. None of which has achieved commercial application because of issues of efficacy, cost and product quality,” he said.
   “If this makes progress, we will be excited,” he said.
   Eugene Kupferman, postharvest specialist at the WSU Tree Fruit Research and Extension Center in Wenatchee, said the low-pressure or hypobaric approach was tried 30 years ago but was very uneconomical and required chambers to withstand vacuum pressure. Atlas Technologies has developed technology to treat fruit on a commercial scale, he said.
   “It will be interesting to see what comes of it,” he said.