Researcher Improves Heat Treatment for Controlling Insects
Mark Nightengale uses a heat treatment process perfected at K-State to protect stored grain from insect pests at Heartland Mills, an organic mill in Marienthal.
K-State research on stored product pest management is helping to protect the environment and benefiting the Kansas food and feed manufacturing industries.
K-State entomologist Bhadiraju "Subi" Subramanyam studies heat treatment as a viable alternative to pesticides in grain, food, and feed manufacturing facilities. His research shows that heating a structure to 122 to 140 degrees and maintaining that temperature for 24 to 36 hours effectively kills insects. This allows processors to produce high-quality products safely and without chemicals, he said.
Heartland Mills, Marienthal, Kan., which produces certified organic grains and flours, uses the method to heat a 19,000-square-foot storage building. General manager Mark Nightengale said heat treatment has been effective.
"No bugs will survive – this includes grain pests, larvae, and eggs. Unlike chemical resistance, bugs have no immunity from heat," Nightengale said.
It has also been good for business.
"With the heat treatment program there are no returned loads because you’ve destroyed grain pests in the building," Nightengale said.
Heat treatment has been used for 100 years, but in the ’30s grain elevators and food processors began using chemicals, said Subramanyam. Methyl bromide, a chemical commonly used to eradicate insects in stored grain, was phased out by the EPA in January 2005.
Subramanyam has devoted the last 15 years to finding viable alternatives –
non-ozone depleting compounds – for controlling pests in stored products. By collecting data on heat tolerance of common grain insects at all stages of development, he’s come up with a model to determine the insect survival rate.
"With this model, we can predict mortality, Subramanyam said. "Once we gather details about the structure – ambient conditions, what is the building made of, layout, how much exposed metal – we can calculate precisely how much heat it will take in BTUs per hour to achieve 100 percent mortality."
The goal is to optimize effectiveness of heat treatment.
"We’re taking what was an art and making it a science," he said.
Knowing exactly how long to heat the structure can lower energy costs, which may be substantial, depending on the size of the treated area and energy source. In the past, heat treatment may not have been feasible because of the way product storage facilities were constructed. Modern structures have been designed with heat treatment in mind.
Heat treatment fits both organic and traditional facilities. Organic mills are a small, yet fast growing segment of the market, and this technology works for them because it leaves no residues and is safer for people working there.
Safety concerns and a strict regulatory environment make heat treatment an attractive option for large processors as well. Industry giants such as ConAgra, General Mills, Quaker Oats, and Nestle-Purina all use the method to some extent and send employees to Subramanyam’s annual workshop, which emphasizes the benefits of this nonharmful alternative.
"Heat treatment is innocuous, you don’t have to worry about emission control and reporting, and there’s no need for residue testing because no chemicals have been applied," he said. "It’s not for everyone, but it is a viable alternative."
Bhadiraju "Subi" Subramanyam
785-532-4092
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785-532-1234
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785-532-2403
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Virgil Small
785-532-6161