Structural Pest Control: The Use of an Enhanced Diatomaceous Earth Product Combined with Heat Treatment for the Control of Insect Pests in Food Processing Facilities

[ Français ]

June 1997
Leadership in the Development of Methyl Bromide Alternatives
Prepared for:

Environment Bureau, Agriculture and Agri-Food Canada
and United States Department of Agriculture

Part of the Canada - United States Working Group on Methyl Bromide Alternatives

By: Paul Fields, Alan Dowdy and Michelle Marcotte

Editor: Anna-Louise Pentland

This article presents the results of research only. Mention of a trademark or proprietary product does not constitute an endorsement or a recommendation for its use by the USDA. All programs and services of the United States Department of Agriculture are offered on a nondiscriminatory basis without regard to race, colour, national origin, religion, sex, age, marital status or handicap.

Mention of any company, association or product in this document is for information purposes and does not constitute a recommendation of any such company, association or product by the Government of Canada.

Photo credits: Michelle Marcotte
Graphic Design and Printing: Bonanza Printing & Copying Centre Inc., Ottawa, Ont.
Ce document est disponible en français
 
TABLE OF CONTENTS

 Foreward
Acknowledgements
Executive Summary
Introduction
Industry Concerns
Heat Treatment for Pest Control
About Diatomaceous Earth and Protect-ItTM
Test Insects
Laboratory Test
Commercial Scale Test
Conclusions About Effectiveness and Synergistic Effect
Participants Notes on Worker Comfort and Safety Issues
References
About the Participants (Contact List)

Table 1. Percent mortality of red flour beetle after high temperature treatment and exposure to Protect-ItTM
Table 2. The rates of application of Protect-ItTM using various methods of application.
Table 3. The survival (%) of insects after heat treatment was complete.
Table 4. The duration of survival in heated and unheated areas, with and without Protect-ItTM .
Table 5. The duration of survival in heated and unheated areas, with and without Protect-ItTM.
Table 6. The temperature at different levels of mortality in heated areas, with and without Protect-ItTM.

Figure 1. Temperatures at the basement, building 12-13 oat mill.
Figure 2. Experimental layout and mean temperatures (oC) for testing combination treatment of heat and Protect-ItTM at Quaker Oat plant.
Figure 3. Experimental layout and maximum temperatures (oC) for testing combination treatment of heat and Protect-ItTM at Quaker Oat plant.
 
FOREWARD

The Montreal Protocol on Substances that Deplete the Ozone Layer is a global agreement intended to protect the ozone layer by reducing the production of ozone depleting substances.

Controls on methyl bromide as an ozone depleting substance have resulted in a critical need for the development of alternatives for its use as a soil, commodity and structural fumigant. Through government research programs and commercial development of alternative technologies and products we are making progress, but more work is needed to ensure good control of pests and plant diseases in agriculture and food processing.

To maximize research collaboration and the development of alternatives, Agriculture and Agri-Food Canada (AAFC) and the United States Department of Agriculture (USDA) entered into an informal agreement to form a working group on methyl bromide alternatives. Agreement was reached to assist research scientists and industry to work together on common problems and projects and to share research results. Since a large amount of Canadas methyl bromide is used in space fumigations for milling and food processing operations it was proposed that Canada lead this area within the working group. This report represents the first report of collaboration between AAFC, USDA Agricultural Research Service scientists and private industry to develop methyl bromide alternatives.

This commercial scale test also illustrates a key component of success in agri-food development. Research partnerships with industry are a cornerstone of AAFCs and USDAs programs. In this regard, we were pleased with the research collaboration of Quaker Oats of Canada and Hedley Technologies Inc. of Vancouver, Canada. Quaker Oats continually assesses pest control methods that contribute to both food quality and environmental goals. Hedley Technologies works with research scientists to test and develop their diatomaceous earth product for pest control. We would like to express our thanks for their collaboration.
David Oulton Dr. Edward B. Knipling
Assistant Deputy Minister Acting Administrator
Policy Branch Agricultural Research Service
Agriculture and Agri-Food Canada U.S. Department of Agriculture
 
ACKNOWLEDGEMENTS

The research participants, Agriculture and Agri-Food Canada, the United States Department of Agriculture and Hedley Technologies appreciate the cooperation of Quaker Oats of Canada for allowing this test to take place in their facility during a heat treatment. Quaker's permission to use photos taken in their facility is very much appreciated. We also thank Quaker Oats management and employees for their cooperation, their assistance and interest in our test. We appreciated the assistance of PCO Pest Control Services Inc.
 
EXECUTIVE SUMMARY

Methyl bromide is used extensively to control insects in food processing facilities. It is slated to be phased-out by the year 2001 in Canada and the United States because it causes significant damage to the Earth's ozone layer. There is a pressing need to find viable alternatives to methyl bromide. Heat treatments to control insect pests of food processing facilities have been used instead of, or in combination with, methyl bromide for more than 15 years by several companies. However, food processors have concerns about heat treatments for various reasons. To address some of these concerns, we began investigating ways to render heat treatment more effective and less costly.

This report covers the use of an enhanced diatomaceous earth (EDE) formulation in conjunction with heat treatment. Diatomaceous earth (DE) damages insect cuticle and causes death by dehydration. We chose Protect-ItTM, produced by Hedley Technologies, because it is as good as or better than other commercial DE insecticides. A Canadian patent application has been made on behalf of Hedley Technologies Inc. and Agriculture and Agri-Food Canada for using heat treatment in combination with DE.

In both laboratory scale and in commercial scale tests, a synergistic effect of EDE and heat was shown. The insects died faster and at lower temperatures. Laboratory experiments using the red flour beetle (Tribolium castaneum) showed insects treated with the EDE at 3 g/m2 and 50oC for 30 minutes were all dead one week after the treatment. By comparison, at least 25% of insects exposed only to heat treatment survived. A field trial was conducted at the Quaker Oats plant in Peterborough, Ontario, Canada during their regular heat treatment. Confused flour beetles (Tribolium confusum) were completely controlled by the dry application of EDE after 13-22 hours or when temperatures reached 41oC. Insects that were exposed only to the heat died after 32-38 hours or when temperatures reached 46 to 47oC.

These results imply that the cost of heat treatment can be reduced and effectiveness improved through the combined use of heat and EDE. The use of heat and Protect-ItTM offers good prospects for success as an alternative to methyl bromide. However, we would like to underline that this test had three elements that are not representative of a full plant application. One, insects were not allowed to escape to untreated areas, which will likely be the case in a full plant treatment. Two, the relative humidity was extremely low (5-19% RH) and in other facilities or at other times of the year, relative humidity could be higher and the effect of the DE may be lessened. Three, in a full plant application, some DE residues will remain, and could continue reducing insect populations after the heat treatment. Therefore, we recommend further work to demonstrate the usefulness of this combination technique on a larger scale.
 
INTRODUCTION

Methyl bromide is either regularly used or serves as an emergency treatment to control insects in the food processing industry. It plays an important role in pest control in these establishments, and pest control is an important facet in food quality and meeting consumer needs. Canada uses about 50% of its total consumption of methyl bromide for control of pests in structures and commodity transport vessels, whereas most other countries only use 15% for this purpose.

Methyl bromide is a controlled substance under the Canadian Environmental Protection Act and the Montreal Protocol on Substances that Deplete the Ozone Layer. In the United States, it is controlled under the Clean Air Act. These actions all require the phase out of methyl bromide as an ozone depleting substance. Canada will reduce its consumption by 25% by 1998 and both countries intend to eliminate its use by 2001, although Canada will still allow it to be used for pre-shipment and quarantine fumigations. Effective and economically viable alternatives must be found to replace methyl bromide.

These ongoing controls, and increasing methyl bromide costs, have already resulted in some companies reducing or eliminating methyl bromide use in favour of heat or other treatments to control pests in food processing facilities. In these instances, enhanced attention to integrated pest management strategies, industry emphasis on sanitation and monitoring are keys to success.
 
INDUSTRY CONCERNS

Some members of the Canadian milling and food processing sectors have concerns about the economic and technical feasibility of heat treatments in their facilities. Replacing the use of chemical treatments, such as methyl bromide, with heat requires considerable capital investment and potentially higher operating costs with this type of treatment. Concern has also been raised that if a heat treatment was ineffective (for whatever reason) then the facility management would have to resort to a chemical treatment to control pests. Methyl bromide remains the most effective pest control treatment for structural and food processing facilities. Some other effective chemicals (such as sulfuryl fluoride - Vikane), are not approved for use in food processing facilities, or near food products.

The economics of heat treatments have also been widely discussed. Some companies of the grain and flour milling and food processing sectors have indicated concerns about effectiveness and others have questions about costs. In general, the slim profit margin of flour milling is a prime consideration when examining any pest control method or capital expenditure.

Canadian milling and food processing facilities vary widely. Some facilities are very old or located in regions with severe winters and industry members are concerned that certain facilities may not be able to maintain the required temperatures for the required time. On the other hand, the Quaker facility, where commercial scale testing took place, has been successfully heat treating for 15 years and has heritage sections (more than 75 years old) with old wood timber beams and wood floor construction. It also includes stone walls and cement-on-soil surfaces known to make heat treatment difficult. Although Quaker is located in Central Ontario, one of the regions of Canada with milder winters, it has conducted successful heat treatments during winter storms.
 
HEAT TREATMENT FOR PEST CONTROL

Using heat to control pests in food processing facilities and other structures has been well researched. In Canada, heat treatments to control stored product insects have been used at Quaker Oats Peterborough food processing plant for more than 20 years (Clarke, 1996). No other Canadian companies are known to rely on heat treatments on a regular basis. Heat treatments are used by many companies in the United States. Some of the factors that may have prevented the widespread adoption of heat treatments are: the capital investment of heating equipment, the need for more frequent treatments and concern about heat damage to buildings and equipment.
 
ABOUT DIATOMACEOUS EARTH AND PROTECT-ITTM

Diatomaceous Earth(DE) is a geological deposit made up of the fossilized skeletons of diatoms, which are unicellular algae that live in seas, lakes, streams, and ponds. Diatoms get their unique shape by absorbing dissolved silica which is then converted into highly ordered shells. When these microscopic plants die, they settle to the bottom of lakes and seas and can form thick layers of nearly pure silicon dioxide. With time and pressure these layers are compressed into the deposits that are known as DE.

Before DE can be used as an insecticide, deposits must be dried and milled to separate individual diatoms which are between 1 to about 100 microns in diameter. The fossilized diatoms are amorphous silicon dioxide which is nontoxic to mammals, and is registered as a food additive in Canada, USA and in many other countries. DE works by adhering to and absorbing the waxy coatings on insects causing their death by dehydration. It has been used to control stored-product pests for centuries. Extensive studies have been conducted on the application of DE as a stored-grain protectant (Banks and Fields, 1995).

There are a number of DE insecticides on the market in Canada and United States today: Dryacide, Insecto, Perma-guard and Protect-ItTM are the main ones used as grain protectants (Quarles and Winn, 1996). They have had limited use, in part because of the widespread use of effective chemical insecticides such as methyl bromide, Malathion, chlorpyrifos-methyl, and phosphine. In addition, earlier DE formulations required very high concentrations, were not always effective and caused other problems. For the DE product, we chose Protect-ItTM. It was developed jointly by Hedley Technologies Inc. and Agriculture and Agri-Food Canada's Cereal Research Centre in Winnipeg and is produced by Hedley Technologies Inc. Protect-ItTM , an enhanced DE (EDE) formulation, has been extensively tested in both the laboratory and in field tests. In these tests, both as a grain protectant and as a structural treatment, it performed as well as or better than other commercial DE products (Korunic and Fields, 1995).

Since food processing facilities usually have low relative humidities, which are reduced even more during heat treatments, a series of experiments was designed to determine if DE could be used to increase the efficacy and speed of heat treatments. Combination treatments have gained acceptance as people search for new ways to control pest populations (Banks and Fields, 1995). Some examples are: phosphine, carbon dioxide and heat and low concentrations of phosphine over long durations with top dressing of diatomaceous earth. If successful, this heat and DE combination method would make it easier for facilities to use heat as a replacement for methyl bromide fumigation. Previous literature gave an indication that silica aerogel and heat are synergistic against the German cockroach at 43oC (Ebeling, W. 1994) (both DE and silica aerogel are made from silicon dioxide).
 
TEST INSECTS

The test insect used for laboratory scale research was the red flour beetle (Tribolium castaneum (Herbst)). For the commercial scale test, the confused flour beetle (Tribolium confusum Jacquelin du Val) was used because, unlike the red flour beetle, it cannot fly and is the main insect pest of food processing facilities.

A flying pest could not be used in the commercial trial since the pests were placed in an open ring. Tribolium species are also good test insects as they are very tolerant to diatomaceous earth.
 
LABORATORY SCALE TESTS

The objective of this research was to examine the combined impact of high temperature and diatomaceous earth on the mortality of the red flour beetle, a cosmopolitan pest of stored cereal products. Additionally, the impact of withholding food after such treatment was also examined.

Methods - Cultures of red flour beetles were maintained at 34°C and 65% relative humidity on a diet consisting of whole-wheat flour and 5% brewers yeast. The rearing temperature was relatively high for this species in order to develop tolerance for higher temperatures within the strain. Adult beetles were placed on fresh diet to lay eggs and transferred to new diet at weekly intervals. By maintaining the beetles in this manner, 1 to 2 week old adult beetles were collected to use in the experiments.

Protect-ItTM, was used in this study. The label rate for Protect-ItTM as a structural treatment is 5 g/m2, therefore, we ran tests at 3 and 7 g/m2. Variability in make-up of diatomaceous earth-based insecticides may mean these results may not be comparable to other diatomaceous earth products (Korunic 1997).

Groups of ten beetles were transferred to 60x15 mm glass petri dishes containing EDE or nothing. The dishes were covered and placed on a programmable thermal cycler and exposed to Protect-ItTM at 34° or 50°C for 15 or 30 minutes. The beetles were placed on the preheated thermal cycler for 2 minutes at 34°C, then the temperature was either maintained at 34°C or increased to 50°C, held for 15 or 30 minutes, then returned to 34°C for 2 minutes. After the treatments, the beetles were removed from the dishes and transferred to clean eight dram shell vials and maintained under original rearing conditions. Some beetles were maintained on about 0.5 g of flour, while others were given no food. Insect mortality was determined after 1 day and 7 days after treatment.

Results - In general, EDE caused higher mortality in all treatments except the ones that were not heated and food was provided (Table 1). Also, heating beetles to 50°C resulted in higher mortality than beetles held at 34°C. Average mortality after one day was 80% for beetles exposed to 50°C compared to 26% for beetles held at 34°C. Mortality after 7 days increased slightly with 86% at 50°C and 40% at 34°C.

In all treatments, mortality increased as the amount of time the beetles were exposed to the high temperature and EDE increased. After 7 days, however, almost all beetles exposed to EDE were dead for all treatment combinations. These results indicate the combination of EDE with high temperature results in greater mortality than the application of heat alone. EDE alone also increased mortality when no food was available.

The availability of food after heat and Protect-ItTM treatment resulted in an average mortality of 42% with food, compared to 64% for beetles that did not have food available. We expected higher mortality would result from withholding food due to starvation as well as better retention of diatomaceous earth on the cuticle. Insects with food would likely dislodge some diatomaceous earth as they walked through the flour. Food would also be a source of water, reducing the desiccation stress. Even a light coating of food material on a surface in a food processing plant would be sufficient to meet the nutritional requirements of an adult red flour beetle. Thus, the situation of a beetle in an environment without food inside a processing plant is unlikely.

With laboratory scale data showing EDE, in combination with high temperature, may be a practical alternative to methyl bromide for managing insects infesting food processing plants, commercial scale testing was recommended.
 
COMMERCIAL SCALE TEST

An initial trial investigating DE and heat synergism was conducted at the Quaker Oats, Peterborough Plant on 13-15th December, 1997. It was inconclusive for two reasons. First, there was a wide variation in floor temperatures between replicates causing mortality at different times. Second, the method of application of Protect-ItTM delivered much less than 1g/m2. This initial trial resulted in the identification of several application methodology issues, application rate inadequacies and test method requirements. The second commercial scale trial reported here took place after laboratory tests (see above) and indicated good prospects for success.

In the current trial we addressed these issues by testing the heat and Protect-It TM combination only in the basement of the oat mill. Of all the sites we tested at Quaker Oats in December 1996, this area had the least temperature variation between replicates and, since the floor was cooler, it provided a better test of effectiveness. The concrete basement floor also minimized opportunities for the pests to escape (compared to hardwood floors). We increased the number of temperature probes and tried different application methods.

Experimental Site, Buildings and Environmental Conditions - Quaker Oats of Canada has both its headquarters and its cereal milling and processing facility in Peterborough, Ontario, Canada. The mill and processing facility occupy a large site, set into a hill and bound on one side by the Otonabee River. During the test weekend, the river was running very swiftly with melting snow and chunks of ice. It was unusually deep and overran its banks in some areas close to the plant. In spite of snow, freezing rain and a very full river close by, the air in the Quaker plant was extremely dry (5 - 19% RH).

The buildings that are heat treated include historical sections with timber beams, timber post and board ceilings, wood floors, and old windows. Other sections have cement floors and new windows. The heat treated areas included original stone foundations set on the soil or more likely, the bedrock of the region. Parts of the building are about 80 years old, and some parts are older, having survived a fire in 1916.



Gleaming hardwood floors and old timbers in the oat mill.

Several sections of the building, particularly in the food processing area, are more modern. Building sections are frequently separated by stairways, interior walls and fire doors. They are joined by tunnels, walkways, open warehouse spaces and an open man-hoist. The facility is serviced by a large steam boiler system; this allowed Quaker to install steam heaters as part of the large capital investment necessary for heat treatment. The variation seen in the Quaker facility makes a good case for the flexibility of heat treatment application in a wide range of operations.

Quaker Oats has conducted heat treatments in all weather conditions. The weather for this test can be accurately described as miserable. The treatment took place on March 14-16,1997; the weekend included one of the worst snow storms of the winter season. Environment Canada Weather Service recorded Peterborough temperatures ranging from -5oC to -11oC throughout the weekend. Friday, precipitation was 24.4 mm of snow and freezing rain. The snow and blowing snow continued through Saturday, but was reduced to accumulations of 1.4 mm. Winds were strong from 30-45 km/h on Friday and 20-35 km/h with gusts to 45 km/h on Saturday. Sunday was calmer with winds of 20 km/h. If a heat treatment can be successful under these weather conditions it should be successful under most conditions.



View of Quaker Oats two days after the winter storm.

Heat treatment at Quaker - Heat treatments are scheduled roughly four times a year; the timing can be moved ahead if needed. Heat treatment is preceded by a thorough cleaning of the facility, although cleaning is a daily component of pest control in this, and most, Canadian facilities.

Heat treatment begins late Friday afternoons and most staff leave at about the same time. Production staff do not return until the Sunday afternoon shift. Heating continues throughout the night, all day Saturday and is finished by Sunday morning.



Equipment left open to allow heat to work efficiently.

The goal is to reach an air temperature at eye level of 50oC and hold that temperature for 24 hours. Unlike chemical treatments, a heat treatment can be easily monitored without the same worker safety concerns or special safety equipment. Pest control, plant sanitation and security staff enter the areas at designated times, inspect the site and record temperatures. While key temperatures are the surface temperatures (where the pests are more likely to be), Quaker has enough experience with the method to allow temperature readings at eye level which are easier for the staff.



A heater in the basement near the windowsill where rings were placed.

In this treatment, most areas reached 50oC after 18 hours from the initiation, at about 10:00 a.m. Saturday morning. Areas that were more difficult to heat, reached the desired temperature after 30 hours after initiation.



A heater in the oat mill near an old timber.

Methods - The test was designed to examine the effects of EDE, heat, the combination of EDE and heat and different application methods. To do this we had four treatments:

1. Heat alone, 2. EDE alone, 3. Heat with EDE, 4. No heat or EDE



A treated and untreated ring on heater on heated basement windowsill showing thermocouple placement.

Three areas were selected for testing; oat mill (basement of building 12-13, heat-treated), hallway (building 4, not heat-treated) and equipment storage and cardboard compacting area(basement, building 11, not heat-treated). For the heated area, we choose a floor of the plant that is the most difficult to heat, the basement of building 12-13, and areas on that floor that were difficult to heat, near windows, doors and walls.



Three test sites in the unheated 4th floor area. The three application methods were also tested here.

Different areas in the oat mill were treated with EDE using four methods of application to the floor:

1. As a dry powder with a power sprayer (Power Dust-er Model # 2250, B. and G. Equipment, PO Box 130, Applebutter Lane, Plumstead Ville, PA, USA).



The power duster application equipment.

2. As a dry powder using a hand duster (Dustin-Miser, R.J. Winmore Inc., PO. Box 1765, Sioux Falls, SD, 57101, USA).



The hand held dust application equipment.

3. As a 20% aqueous solution using a hand sprayer (Spray Doc, Gilmor Group, Mississauga, ON, L5S 1P7, fitted with a Teejet 11002vs spray nossle, this gave a flat fan spray with 70 ml/10 s).



The spray application equipment.

4. Distributed in measured amounts (1, 3 and 7 g/m2) into rings (Fig. 1).



Paul Fields with the treated and untreated rings ready for measured amounts of diatoceous earth in the heated basement.

Where equipment was used to apply the EDE, it was operated by a technician with PCO Pest Control Services Inc. Where the EDE was distributed in measured amounts into the rings, the participants evenly distributed it with a small brush. The formulation of EDE applied in this test used a different geological source of DE than the commercially available Protect-ItTM.



Treated and untreated rings in the unheated area, and data logging equipment.
Treated rings were placed in the areas previously covered by plastic.
In these areas the floor looks darker.

The new source of DE has less than 1% crystalline silica. Protect-ItTM is currently recommended to be applied as a dry powder at 5 g/m2.

Each treated area was in a separate part of the oat mill basement, with about 1 X 2m being treated. The application was carried out between 14:00 hours and 16:00 hours March 14, 1997 after the preheat cleaning was completed. Sections in each treated area were covered with plastic sheeting to prevent EDE from being applied to areas that were to serve as untreated sections.
To estimate the amount of EDE applied, plastic plates (10 cm x 10 cm, area = 0.01 m2 ) were preweighed with a Zip-Lock plastic bag and double backed tape, placed in areas before spraying, collected immediately after application, placed in plastic bags and reweighed. There were 3 plastic plates per treatment.

To allow insects to be exposed to the heat treatment with space to move and yet prevent their escape into the food processing facility, they were placed in ABS plastic rings (15 cm diameter, 2 cm high, area of 0.018 m2 ). The rings were coated with liquid Teflon (Fluon) to prevent insects from climbing out. The rings were set down on the floor and sealed along the outside edge using plasticine to prevent insects from escaping via cracks between the ring and the floor. There were 3 rings for each treatment. Within a treatment, rings were about 5 cm apart.

Confused adult flour beetles were placed in vials with 10 g flour, 2 days prior to the test at Quaker Oats. They were sieved out of the flour and placed in the rings between 15:00 hours and 17:00 hours March 14. There were 50 individuals per ring. Mortality was checked at 60 minute intervals. Dead insects were removed after each inspection.



Doug Morrissey preparing the test rings.
Note the plastic covered areas that will later provide a space for untreated rings in the spray area.



Sieving the insects out of the flour before they are placed in the treated rings.



Paul Fields operating the data logger used to record floor temperatures.

Floor temperatures were taken in both treated and untreated sections (Fig. 1-3). Temperatures in the heated area were taken every minute and averaged and recorded every 10 minutes using a data logger. Temperatures were also measured as usual by Quaker Oats employees. These temperatures were taken hourly at eye level in the four corners of each floor using a digital thermometer



Doug Morrissey using the power duster to spray the unheated areas.



Blaine Timlick counting pests in the heated basement.





Results- Air temperatures as measured by the data logger were above 50oC by 19:00 on March 14 (Fig. 1). Air temperatures measured by Quaker Oats employees in the four corners of the basement were all greater than 50oC by midnight March 14. Some fans on the unit heaters were turned off to prevent overheating. One set of rings, those set up beside the outside door, was in the airflow of one of the unit heaters. When this fan was turned off,the temperature in these rings and those on the closest window declined sharply. Floor temperatures in unheated areas were 16.9-17.1oC for the power dusted area and 20.4-23.7oC for the hand dusted and sprayed areas.

Relativity humidity started at 19% and declined to 5% in the heated basement. It remained constant in the unheated basement (power dusted) at 14% and ranged between 12% and 15% RH in the other unheated areas (sprayed, hand dusted and measured amounts). There was no attempt to calibrate the three different instruments used to measure relative humidity. Accuracy for these instruments is 5% RH. Low relativity humidity increases the efficacy of DE and added to the effectiveness of this test. However, in other facilities, at other times of the year (in the summer) or other locations (US southeast, northern Europe) relativity humidities will be higher. Previous laboratory tests underline the importance of relative humidity. Protect-ItTM at 3g/m2 at 25oC found 100% mortality after 4 days for the red flour beetle at 55% RH, but only 25% mortality at 75% RH (Korunic and Fields, 1995).

Application Rates- Using an electrically-powered duster to apply the EDE gave a fine, even application of approximately 1-2 g/m2 (Table 2). Using a hand-powered duster gave heavier application rates, approximately 4 g/m2, with uneven coverage. Water spray application left visible residues and gave 4-8 g/m2.

Insects - We used three ways to measure the effectiveness of control of the combination method: For the first two measures, we report the durations and temperatures for the first, median (50%) and last insect to die. All insects in the heated area that were treated with EDE died before the end of the treatment (Table 3). There was some survival of insects in some of the heated areas that were not treated with EDE (Table 5).
 
CONCLUSIONS ABOUT EFFECTIVENESS AND SYNERGISTIC EFFECT OF THE COMBINATION TREATMENT

1. In the heated area, dry application of EDE gave 100% mortality of the confused flour beetle adults after 13-22 hours and 41oC compared to untreated insects that required 32-38 hours and 46-47oC. In several sections of the floor, heat alone did not provide complete control (Tables 4 - 6).

2. Using an electrically-powered duster to apply the EDE resulted in a fine, even application of approximately 1-2 g/m2. This method places considerable dust in the air. It will require applicator training and the use of dust masks and eye goggles. Using a hand-powered duster gave heavier application rates of approximately 4 g/m2, with uneven coverage. Water spray application left visible residues and caused little to no increase in insect mortality.

3. The use of heat and Protect-ItTM offers promise to be an alternative to methyl bromide. However, we would like to underline that this test had three elements that may not be representative of a full plant application. One, insects were not allowed to escape to untreated areas, which will likely be the case in a full plant treatment. Two, the relative humidity was extremely low (5-19% RH) and in other facilities or at other times of the year relative humidity could be higher and the effect of the DE may be lessened. Three, in a full plant application, some DE residues will remain, and could continue reduce insect populations after the heat treatment. Therefore, we recommend further work to demonstrate the usefulness of this combination technique on a larger scale, perhaps by dusting an entire floor and through use in inaccessible areas or hard-to-clean areas. Pest populations should be estimated for at least one month before and several months after treatment.

4. A Canadian patent application has been made on behalf of Hedley Technologies Inc. and Agriculture and Agri-Food Canada for using heat treatment in combination with DE (Fields, 1997).
 
PARTICIPANT'S NOTES ON WORKER COMFORT AND SAFETY ISSUES

Concerns have been voiced that DE used in a food processing facility might cause worker annoyances, comfort or safety issues. To obtain some information on this aspect all four participants involved in the test were interviewed for anecdotal comments on their response to contact with DE. In addition, we answered questions from Quaker Oats employees during the tests and asked if there were questions raised after the test was finished.

Since we were testing application methods to determine how to attain the desired concentrations with the equipment to be tested, it can be assumed we were not as experienced or efficient as a trained pest control operator would be. We were in contact with higher concentrations of EDE, airborne and on our skin than would be the case for workers in a food processing establishment. In addition, because the work involved repeated and very close (in terms of cm) inspection of the pests and EDE treated areas, we were exposed to it many times over several hours.

If DE were to be sprayed or otherwise applied in inaccessible areas, cold floor and wall junctions or hard to heat areas it would not be sufficiently airborne and the residues would not likely be great enough to cause discomfort to workers.

In terms of safety precautions, test participants wore ordinary disposable 3M Dust and Mist Respirator face masks (National Institute of Occupational Safety and Health approval # TC - 21C - 401) fitted snugly over nose and mouth. The masks were only worn during EDE application or when the dust was heavy in the air. We usually left heavily dusty areas and waited until the dust settled. We did not wear dust masks at other times, when counting pests, for example. None of us wore dust goggles, but this would be recommended, particularly for the technician doing the application. We wore short sleeves, mostly because it was very hot in the treated area. We wore hair and beard nets as standard procedure in a food processing facility.

We advised Quaker Oats employees we encountered during application that they should stay away for awhile and then later answered their questions. They were mainly curious, mostly because we were placing so many insects in their establishment. While most Quaker employees were not present during the test, the test started as people were leaving. During the weekend, plant managers, sanitation, engineering, safety and security staff made regular rounds in our test areas. An electronic-mail message sent to Quaker employees prior to the test about DE as a pest control method seemed to allay concerns.

None of the participants noted any skin, respiratory, nose, eye or mouth annoyances and we were not uncomfortable working with the Protect-ItTM, either during treatment or after. One contact lens wearer did not notice any discomfort even over several hours of exposure.

The participants recommend simple precautions to avoid inhalation and eye irritation. Dust masks and safety goggles should be worn during application and in dusty areas. These precautions are particularly advised for pest control technicians who would be more exposed to the dust. If using application methods that blow a lot of DE into the air, start at the far corner and back out of the room as it is applied.
 
REFERENCES

Banks, H.J. and Fields P.G. 1995. Physical methods for insect control in stored grain ecosystems. In: Jayas, D.S., White, N.D.G. and Muir, W.E. (editors), Stored Grain Ecosystems. pp. 353-409.

Clarke, L. 1996. Heat Treatment for Insect Control. Proceedings of the Workshop on Alternatives to Methyl Bromide. pp. 59-65, Toronto, Canada May 30-31.

Ebeling, W. 1994. Heat and silica aerogel are synergistic. IPM Practitioner February.16:11-12.

Fields, P.G. 1997. Heat treatment and diatomaceous earth for insect control. Canadian Patent Pending.

Korunic, Z. 1997. Diatomaceous earth as a group of natural insecticides. Journal of Stored Product Research. in press.

Korunic, Z. and Fields, P.G. 1995. Diatomaceous earth insecticidal composition Canadian and US Patent Pending.

Quarles W. and Winn, P.S. 1996. Diatomaceous earth and stored product pests. The IPM Practitioner. 18:1-10.

 
Table 1. Percent mortality of red flour beetle after high temperature treatment and exposure to Protect-ItTM.
Post
Exposure
Duration
(days)		 DE Dose
(g/m2)		 Food After Treatment
No Food After Treatment
15 min exposure
30 min exposure
15 min exposure
30 min exposure
34°C 50°C
34°C 50°C
34°C 50°C
34°C 50°C
1 0 0 47 b
0 88
0 b 38 b
0 b 72 b
3 3 70 ab
2 98
72a 75 a
82 a 97 a
7 3 87 a
3 98
57 a 87 a
85 a 98 a
LSD1 NS 30
NS NS
31 28
20 22












7 0 0 52 b
8 96
22b 50 b
17 b 82
3 7 75 a
8 98
100 a 100 a
100 a 100
7 8 82 a
7 100
100 a 100 a
100 a 100
LSD1 NS 20
NS NS
11 20
9 NS
1. Least Significant Difference, = 0.05
Within a column for each duration, means followed by the same letter are not significantly different =0.05

 
Table 2. The rates of application of Protect-ItTM using various methods of application.
Application
Method 		Area Change in Weight2 (g/m2) ± SEM
Significant Differences 1
DE-Treated Untreated
Power Duster Heated -1.9 ± 1.2 -0.2 ± 1.2 ns
Unheated 1.4 ± 0.3 0.1 ± 0.3 *




Hand Duster Heated 3.7 ± 0.9 1.3 ± 0.6 *
Unheated 4.0 ± 0.8 0.0 ± 0.6 **




Hand Sprayer Heated 8.6 ± 1.8 0.0 ± 0.4 **
Unheated 3.8 ± 0.3 -0.6 ± 0.3 **
1. One-tailed t-test, ns= no significant difference, * = p< 0.05, **= p<0.01
2. Negative values are probably due to errors in measuring initial weight.

 
Table 3. The survival (%) of insects after heat treatment was complete.
Application Method Area Survival (%) ± SEM Significant Differences 1
DE-Treated Untreated
Power Duster Heated
Unheated		 0 ± 0
100 ± 0		 9 ± 4
100 ± 0		 *
ns
Hand Duster Heated
Unheated		 0 ± 0
9 ± 6		 0 ± 0
99 ± 1		 ns
**
Hand Sprayer Heated
Unheated		 0 ± 0
100 ± 0		 0 ± 0
100 ± 0		 ns
ns
Measured 3 g/m2 Windows Heated 0 ± 0 3 ± 2 ns
Measured 3g/m2 Doors Heated 0 ± 0 17 ± 15 ns
Measured 1 g/m2 Floor Heated
Unheated		 0 ± 0
16 ± 10		 15 ± 4
100 ± 0		 *
**
Measured 3 g/m2 Floor Heated
Unheated		 0 ± 0
0 ± 0		 15 ± 4
100 ± 0		 *
**
Measured 7 g/m2 Floor Heated
Unheated		 0 ± 0
0 ± 0		 15 ± 4
100 ± 0		 *
**
1. One-tailed t-test, ns= no significant difference, * = p< 0.05, **= p<0.01

 
Table 4. The duration of survival in heated and unheated areas, with and without Protect-ItTM.
Application Method Area Time of Death Duration (h) ± SEM
DE-Treated Untreated
Power Duster Heated First
Median
Last		 11 ± 1
17 ± 1
22 ± 1		 22 ± 0
35 ± 1
x
Unheated First
Median
Last		 x
x
x		 x
x
x
Hand Duster

Heated First
Median
Last 		 5 ± 0
10 ± 1
14 ± 1		 18 ± 2
30 ± 1
38 ± 4

Unheated First
Median
Last 		 7 ± 2
18 ± 2
x 		 x
x
x
Hand Sprayer Heated First
Median
Last		 11 ± 3
21 ± 2
28 ± 3		 15 ± 2
27 ± 03
32 ± 1
Unheated First
Median
Last		 x
x
x		 x
x
x
1. One-tailed t-test, ns= no significant difference, * = p< 0.05, **= p<0.01
x Not achieved during heat treatment

 
Table 5. The duration of survival in heated and unheated areas, with and without Protect-ItTM.
Application Method Area Time of Death Duration (h) ± SEM Significant Differences 1
      DE-Treated Untreated  
Measured Amounts
3 g/m2 Windows 		Heated First
Median
Last		 9 ± 0.3
13 ± 1
19 ± 2		 21 ± 2
35 ± 0
x		 **
**
-
Measured Amounts
3 g/m2 Doors		 Heated First
Median
Last		 6 ± 0
9 ± 0.3
15 ± 0		 22 ± 0
32 ± 2
x		 **
**
-
Measured Amounts
3 g/m2 Door		 Heated
(in direct path of heated air)		 First
Median
Last		 3
5
6		 8
8.5
10		 -
-
-
Measured Amounts
1 g/m2 Floor		 Heated First
Median
Last		 9 ± 0.3
14 ± 0.2
21 ± 1		 20 ± 3
36 ± 2
x		 *
**
-

Unheated First
Median
Last		 12 ± 2
29 ± 3
x		 x
x
x		 -
-
-
Measured Amounts
3 g/m2 Floor		 Heated First
Median
Last		 6 ± 1
9 ± 0.4
15 ± 1		 20 ± 3
36 ± 2
x		 *
**
-

Unheated First
Median
Last		 11 ± 1
16 ± 0.2
27 ± 2		 x
x
x		 -
-
-
Measured Amounts
7 g/m2 Floor		 Heated First
Median
Last		 5 ± 0.3
9 ± 1
13 ± 2		 20 ± 3
36 ± 2
x		 *
**

Unheated First
Median
Last		 8 ± 2
15 ± 0.5
23 ± 5		 x
x
x		 -
-
-
1. One-tailed t-test, ns= no significant difference, * = p< 0.05, **= p<0.01
x Not achieved during heat treatment

 
Table 6. The temperature at different levels of mortality in heated areas, with and without Protect-ItTM.
Application Method Area Time of Death Temperature (C) ± SEM Significant Differences 1
DE-Treated Untreated
Power Duster Heated First
Median
Last		 38.7 ± 1.0
40.0 ± 0.8
42.6 ± 0.6		 43.2 ± 0.7
46.3 ± 0.5
x		 **
**
-
Hand Sprayer Heated First
Median
Last		 40.0 ± 2.0
43.9 ± 1.4
45.4 ± 1.8		 42.4 ± 0.7
43.5 ± 1.7
46.9 ± 0.4		 ns
ns
ns
Hand Duster Heated First
Median
Last		 35.1 ± 0.3
38.8 ± 0.4
40.7 ± 0.6		 41.4 ± 0.4
44.4 ± 0.4
46.3 ± 0.3		 **
**
**
Measured Amounts
3 g/m2 Windows 		Heated First
Median
Last		 36.6 ± 0.8
37.5 ± 0.5
41.5 ± 1.7		 40.9 ± 1.2
44.2 ± 1.6
x		 *
**
-
Measured Amounts
3 g/m2 Doors		 Heated First
Median
Last		 35.8 ± 2.0
37.8 ± 1.1
40.2 ± 0.5		 42.7 ± 0
47.4 ± 0.1
x		 *
**
-
Measured Amounts
3 g/m2 Door		 Heated
(in direct path of heated air)		 First
Median
Last		 45.5
48.5
49.9		 51.9
51.9
x		 *
**
-
Measured Amounts
1 g/m2 Floor		 Heated First
Median
Last		 37.5 ± 0.4
39.6 ± 0.3
41.9 ± 0.5		 41.4 ± 0.9
46.4 ± 0.4
x		 -
-
-
Measured Amounts
3 g/m2 Floor		 Heated First
Median
Last		 35.7 ± 0.4
37.9 ± 0.1
40.4 ± 0.1		 41.4 ± 0.9
46.4 ± 0.4
x		 **
**
-
Measured Amounts
7 g/m2 Floor		 Heated First
Median
Last		 35.2 ± 0.1
37.2 ± 0.3
39.0 ± 0.8		 41.4 ± 0.9
46.4 ± 0.4
x		 **
**
-
1. One-tailed t-test, ns= no significant difference, * = p< 0.05, **= p<0.01
x Not achieved during heat treatment
 
 
ABOUT THE PARTICIPANTS

Paul Fields has worked for eight years as a research scientist at the Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, Manitoba. Pauls research involves extensive collaboration with Canadian grain and cereal sector and with suppliers of pest control products and technologies. Paul designed, conducted and managed this commercial scale test and was principal author.

Alan Dowdy has conducted research on monitoring and movement of stored product insects and alternatives to conventional insecticides for eight years as a research entomologist with the Grain Marketing and Production Research Centre, USDA - ARS in Manhattan Kansas. Part of Alans research assignment involves collaborative projects with grain processors that use heat for insect management in processing plants. Alan conducted and provided the laboratory research that this test was based on and acted as report reviewer.

Michelle Marcotte is President of Marcotte Consulting Inc., Ottawa, Canada. Michelle specializes in agri-food business management consulting with particular emphasis on market development of new food processing technologies and products. Michelle is a member of the United Nations Methyl Bromide Technical Options Committee. Michelle assisted with the test, took the photos and wrote this report in collaboration with the researchers.

Livingston Clarke is Manager of Food Hygiene Services with Quaker Oats Canada, stationed at Peterborough Ontario. For almost 30 years Liv has managed change in sanitation and pest control in Quaker Oats milling and food processing facilities. Collaboration with researchers to determine the best sanitation and pest control practices has assisted Quaker to meet its product quality and environmental goals. Liv managed the heat treatment, arranged for Quakers collaboration with this test and acted as report reviewer.
 
Anna-Louise Pentland has worked in various capacities with Agriculture and Agri-Food Canada for the past three years. She is currently an Environmental Analyst with the Environment Bureau of Policy Branch in Ottawa. She edited and coordinated the production of this publication.

Blaine Timlick is a technician currently working with Agriculture and Agri-Food Canada to test effectiveness and develop application methods for Protect-ItTM, a diatomaceous earth product with improved pest control properties. The financing to support the diatomaceous earth project is provided by AAFCs Matching Investment Initiative and Hedley Technologies Inc. Blaine has worked in pest control research, regulatory and commercial technical positions in Canada, the United States and Australia. Blaine conducted this test and acted as a report reviewer.

Peter Ormesher is the President of Hedley Technologies Inc. the supplier of the enhanced diatomaceous earth product, Protect-ItTM. Hedley partially funded this research unto methyl bromide alternatives under a Research and Consulting agreement with Agriculture and Agri-Food Canada. Peter is a member of the Canada-United States Working Group on Methyl Bromide Alternatives. He acted as a report reviewer.

Linda Dunn is an Environmental analyst with the Environment Bureau of Agriculture and Agri-Food Canada and Chair of the Canada-United States Working Group on Methyl Bromide. She acted as a report reviewer.

Bernie McCarthy is a project manager for PCO Services Inc. He acted as a report reviewer.

Doug Morrissey is a licensed pest control operator with PCO Services Inc. He applied the diatomaceous earth at the test sites, testing the ease of application and other factors of the equipment under consideration and providing feedback about the practicality of use diatomaceous earth in a food processing facility.

Paul Fields
Cereal Research Centre
Agriculture and Agri-Food Canada
195 Dafoe St.
Winnipeg, Manitoba, Canada, R3T 2M9
Telephone: 204-983-1468, Facsimile: 204-983-4604
E-mail: pfields@agr.gc.ca

Alan Dowdy
Grain Marketing and Production Research Centre
United States Department of Agriculture - Agriculture Research Station
1515 College ave.
Manhattan, Kansas, USA, 66502
Telephone: 913-776-2719,  Facsimile: 913-537-584
E-mail: dowdy@crunch.usgmrl.ksu.edu

Michelle Marcotte
Marcotte Consulting Inc. , 443 Kintyre Private
Ottawa, Ontario, Canada, K2C 3M9
Telephone: 613-727-1469,  Facsimile: 613-727-8541
E-mail: marcotte@magi.com

Livingston Clark
Quaker Oaks Company of Canada
Quaker Park , Peterborough, Ontario, Canada, K9J 7B2
Telephone: 705-743-6370, Facsimile: 705-876-4116

Shelia Jones
Environment Bureau
Agriculture and Agri-Food Canada
Sir John Carling Building
930 Carling Avenue, Room 367
Ottawa, Ontario, Canada, K1A 0C5
Telephone: 613-759-7300,  Facsimile: 613-759-7238
E-mail: jonessh@agr.gc.ca
Since the publication of this report Shelia Jones has replaced Linda Dunn

Peter J. Ormesher
Hedley Technologies, Inc.
1540-800 West Pender Street
Vancouver, British Columbia, Canada, V6C 2V6
Telephone: 604-685-1247,  Facsimile: 604-685-6039
E-mail: hedceo@ibm.net

Bernie McCarthy
PCO Pest Control Services, Inc.
170 Robert Speck Parkway
Mississauga, Ontario, Canada, L4Z 3G1
Telephone: 905-949-8778 Facsimile: 905-949-8739

RELATED LINKS
USA EPA's Methyl Bromide Phaseout Web Site

UNEP Methyl Bromide Technical Options Committee

Enviroment Canada's Methyl Bromide Fact Sheet