Insect Rate Fumigations in Structures Require Special Considerations

August 2024 Edition:

by: Curt Lilleodden, Iowa Regional Manager

I remember my first structural fumigation. It was the summer of 1992, and I was still pretty green, with only a little over a year of experience in the pest control business under my belt, long before my years with FSS.

It was a hot August day, a crew of three, and a 100-year-old brick building in Northern Minnesota, which was not in the best shape. Our target pest was cheese mites if memory serves me correctly. We were using Methyl Bromide – widely used back then, limited and only specific uses today. Our fumigation crew was too small for the job. Sealing and preparations went well into the night. Finally, after a nervous fumigant introduction around midnight, it was my first time wearing an SCBA, which in this case was SCUBA gear (the owner had a buddy who owned a dive shop) – I recall feverishly working the building perimeter with a Halide detector testing for and sealing leaks that seemed almost too numerous to count.

Finally, around 2 am and after taking readings with the Mrs. vacuum cleaner and some colorimetric tubes, we felt good about the conditions and got some rest. In the middle of the night a wild storm rolled through, and I arrived at first light to find one of our largest seals had let loose and was flapping in the wind, like a giant flag of failure! Taking readings and finding little or no gas left, I felt disheartened, although I believe in the end, we were semi-successful, at least we couldn’t find any live mites afterwards. Other than no one getting hurt, I can’t think of much else that could have gone wrong on that job.

Many things have changed in the 32 years that have passed since that hot August day; the fumigants we primarily use, our monitoring equipment and certainly written plans and safety considerations have improved, but many of the basics still are the same.

To have a successful insect rate fumigation there are several factors to be considered including: the commodity being fumigated and target pest, desired level/life stage of control, temperature, downtime available, and the suitability of the structure itself.

First, you need to correctly identify the target pest and determine what fumigant you plan to use. You must also be certain that it is legal to fumigate the commodity by consulting the label. Most stored product pests are insects that have four distinct life stages: egg larva, pupa and adult. Your target pest may be affected differently based on the specific insect species and life stage, depending on what fumigant is being used. Is it adults and the more active stages or is control a high percentage of the egg population also the goal? The amount of gas and time needed can vary greatly in these various stages of the insect depending on the temperature. Unlike warm-blooded animals, the physiological functions of a cold-blooded arthropod are greatly impacted by temperature. Generally, the warmer it is, the more active the insect. As temperatures increase, metabolism and respiration will increase – to a point of course. With the main route of entry for fumigants being through respiration, knowing the temperature where the insect is most active and thus most susceptible to the fumigant is necessary for calculating the correct dosage rates to achieve success.

The amount of time that a structure can be vacated and secured, the time we have available to hold the gas and safely remove it again before reoccupation, along with the building’s half loss time (how many hours before one-half of the original amount of fumigant introduced has escaped) will also determine fumigant dosage rates. Some structures require a lot more sealing than others to hold the fumigant and some simply are not tight or structurally sound enough to hold the amounts necessary to achieve the desired level of control, either safely or economically. Adjacent properties must also be considered. Fumigant that escapes from the target structure whether during introduction or ventilation must never exceed levels that could put nearby occupants and bystanders at risk.

Even after all of this has been assessed, considered, and planned for, we still need to account for the weather. High winds, a fumigator’s worst enemy during the hold time, can pull, push, and draw gas from the structure. Temperature can also cause the gas to behave differently. There are instances, especially with taller buildings, when the range in temperature from within the structure to the temperature outside, can affect how well it will hold gas. Warm buildings in warm weather usually hold gas better than warm buildings in cold weather. The same structure may not hold the fumigant as well in November as it did in July and may require more fumigant to achieve the same results. If a building or structure is not adequately insulated or heated, it may not be suitable to fumigate for insects at all during colder weather.

Insect-level fumigations can be a significant investment to protect your product, your building, and your Brand. It is important that careful planning be given to the process, considering commodity and target pest, desired life stages to be controlled, temperature, downtime available, the suitability and sealing requirements of the structure.

Long gone are those early developmental years of my career, with many successes and lessons (a few the hard way) learned. There are more stories of fantastic and wild fumigations that I could share, but now, as I go into my 15th year of structural fumigations with FSS, I see how our company, with our experience, knowledge, and expertise, stands out above the rest and realize the benefit and the need of hiring specialists to provide a safe, successful, and more economical fumigation.