GFMT Article: Controlling insects with heat

Today we take a look at 'Controlling insects with heat' by Dr Raj Hulasare, Burnsville MN, USA. Origbially published in the March/April 2012 issue of GFMT magazine, the feature examines the advantages of using thermal radiation to control stored product pests.

Read full article with pictures here or scroll down for just the text

Controlling insects with heat

by Dr Raj Hulasare, senior scientist and product manager, Thermal Remediation Division of Temp Air, Burnsville MN, USA

  

Thermal remediation is a high-temperature treatment performed in a scientific manner to eradicate stored product pests, without any structural damage to the facility or storage structure.

Thermal remediation kills bugs safely and effectively, if you know how to apply and use the heat properly. Heat treatment is an effective Integrated Pest Management (IPM) tool to get rid of insect infestations.

This is a non-toxic and safe treatment method which is growing in popularity.

An old idea with a new purpose

Using heat to control pests is not new. High- temperature heat treatments to control moths first were used by the French in the 1760s, more than 245 years ago. Heat treatment has been performed successfully by major food and grain-processing companies for the past 40 years.

Why is heat treatment making a comeback?  There are three key reasons:

Consumer preference for pesticide-free products

Heightened interest in eco-friendly technologies or using the ‘Go Green’ approach

Increased resistance of insects to chemicals

A safe method

Heat is an effective, non-chemical, non-toxic, non-residual and non-corrosive alternative to chemical fumigation. It is an eco-friendly approach for utilising pest management practices, without the chemically-associated environment or health risks to people, animals or surroundings. With the 1987 Montreal Protocol and the 1998 amended US Clean Air Act, mandates were established to start phasing out the production of methyl bromide due to its connection with depleting the ozone layer.

While methyl bromide is going through a re-registration process, its use has been subjected to more restrictions. The resistance of insects to phosphine and, to a lesser extent, to methyl bromide is also now an acute problem worldwide.

This is another reason for the need to increase the arsenal of methods to control insects effectively and economically. It’s also why the interest in using heat treatment to control insects continues to grow.

Research on efficacy of heat

Comprehensive scientific data on the effects of high temperatures on various stored-product pests and their life stages (eggs to adult) was not available for many years.

Consequently, Temp Air sponsored research at the Department of Grain Science and Industry at Kansas State University (KSU) in 1999. Temp Air offers integrated solutions to heat treat food processing plants and metal and concrete silos of all sizes, with a range of heater sizes, wireless temperature monitoring systems, and on-site training for do-it-yourself subsequent treatments. Research findings show that most insects die in less than an hour at 50 deg C (122 degrees F), and all life stages are killed when exposed for more than five hours.

A collaborative effort

Temp Air also is collaborating actively with pest control companies, universities (for example, Purdue University, KSU and the University of Minnesota) and autonomous institutes (for example, the Propane Education Research Council [PERC] and the Gas Technology Institute) to develop products and protocols for various heat applications.

For example, Temp Air collaborated with Purdue University in 2009 on a project funded by PERC to heat treat on-farm bins and silos with a trailer-mounted, self-contained, propane-fuelled unit (MHT-1500) that also has potential industrial applications in the organic and conventional processing industries.

With partial funding from PERC, Temp Air also continues to collaborate with KSU's Department of Grain Science and Industry on US Department of Agriculture and Environmental Protection Agency projects.

Patented heat treatment process

Temp Air’s patented heat treatment process uses 100 percent outside air to create positive pressure within an enclosed structure to achieve temperatures lethal to insects at all life stages. It so far has proven to be an extremely effective means of controlling stored-product pests.

The process uses a combination of direct-fired (natural gas, propane or steam-fuelled) make-up heaters, fans and ductwork, to control the flow of air and maintain uniform temperature profiles throughout the treatment area.

The positive pressure throughout the treated space pushes hot air into corners, cracks, and crevices making it virtually impossible for pests to hide anywhere. A dry heat of at least 49 deg C (120 degrees F) is produced, which then is held evenly throughout the treated space, for up to 24 hours or for the time required for the application.

Heat treatment of processing facilities

Temp Air has been performing heat treatments successfully during the past decade in the food industry. This includes flourmills, food processing plants, bakeries, and warehouses. The process of heat-treating a processing facility involves four steps:

A walk-through visit at the facility with operational staff to assess the feasibility of a heat treatment. This includes discussions on equipment and a sprinkler system that can handle high temperatures

Developing an engineering design covering energy and equipment requirements, duct sizing, and fuel usage to estimate the cost of a heat treatment

Mobilisation of equipment and personnel to the site for setup

The actual heat treatment begins, starting first with a joint inspection before the start up

Then, the temperature is ramped up gradually, and the real-time temperature is monitored (using wireless temperature sensors) and then held steady for 24 hours.

During this 24-hour period, frequent inspections are made to monitor insect activity and to identify any cold pockets that may need fixing. Afterwards, the treatment area is cooled down, and the treatment is documented, in order to generate a final wrap-up report that can be discussed with the customer. The entire heat treatment of a structure is completed in less than 36 hours.

Additionally, heat treatment allows for the opportunity to identify pockets and areas of infestation, where insects still may survive and thrive in the treated area(s).

During the 24-hour treatment period, observing the insects’ activity and movement from hotter areas to cooler areas and looking for any signs of re-emergence in the cooler areas make it possible to identify the critical spots of infestation.

During a heat treatment, inspections can be made to identify areas of insect emergence from cracks or crevices. A subsequent treatment of cracks and crevices then can be done after the main heat treatment.

Limitations of heat treatment

There are a few limitations to using heat to control insects. For example, Temp Air discourages heating products in warehouses. Food and stored products are good insulators, and the heat may not penetrate the products well, and it also may alter the properties of the product(s). Heat also may damage packaging materials such as plastic.

Advantages of heat treatment

Heat kills all the life stages of insects, from egg to adults, unlike chemicals, where higher dosages may be required for egg-kill

Heat is nontoxic, noncorrosive and non-residual

An entire facility or sections of the facility (spot treatments) can be heat treated, while other areas remain operational

No mandatory evacuation in adjacent untreated areas, such as a warehouse, shipping area, or office, is necessary. These areas can function normally

No extensive sealing required, except for the doorways and exit points

Similarly, treating a bin or silo full of product is not advisable, as the quality

parameters of the stored product or commodity may become altered.

However, heat-treating empty bins and silos can be extremely effective.

Heat treatment of bins and silos

Temp Air has been very active in offering heat remediation solutions for treating empty bins and silos on farms and in food processing plants.

Presently, empty on-farm bins and silos are fumigated chemically or treated prior to harvest and loading fresh grain. The floors of bins and silos accumulate broken grain and fine matter that harbours insects and mould spores.

In milling and grain handling facilities, residual insect populations in bin hoppers and floors can become a major source of re-infestation, as grain gets warmer. In some cases, chemical treatments may not penetrate well into a mass of insects, or the insecticide spray may drip through the clogged perforated floor but still not reach the insects in the spoiled grain underneath the screen.

Also, blowing diatomaceous earth through the fan doesn’t guarantee uniform application, and phosphine fumigation requires a licensed applicator. Using heat to treat bin floors and other grain holding areas can overcome these obstacles.