Time and Temperature

July 2025 Issue: Steve Granzow

Stored Product Insects sure do know how to “make hay while the sun is shining”. These cold-blooded deviants are affected in so many ways as temperatures increase towards their optimal range. Most stored product insects can reach their highest levels of reproduction between 75 and 90˚F. Facilities that had little to no evidence of activity in the previous months can start to see activity as interior temperatures approach this range. Stored Product Insects are very good at overwintering, and as temperatures increase, so does the insect’s activity, metabolism, and ability to reproduce.  Insects lay more eggs, more frequently, at temperatures in this range. The eggs can hatch faster more quickly, and the larvae become breeding adults sooner. It often leaves little time between finding activity and needing to do something about it. The good news is that time and temperature can help in the treatment of these target pests.

Fumigants either suffocate or poison insects at the cellular level. Insects “breathe” a little bit differently than we do. Insects do not have lungs. They have networks of tubes called trachea that deliver Oxygen directly to their cells and tissues. This is known as cellular respiration and is part of their metabolic process. As all other parts of an insect’s functions increase with optimal temperatures, so must an insect’s metabolism. This allows insects at all life stages to have a higher “uptake” of a fumigant applied to a space. Insect eggs have a significantly slower metabolism than their larva or adult counterparts, but even they become more susceptible when temperature is at optimal range, requiring less total fumigant to get the job done.

Structural Fumigations are designed and measured in units of concentration/time or “C/T”. When monitoring a fumigation, the concentration readings are added for every hour of exposure. That means lower concentrations over longer periods of time are just as effective as shorter treatments at a higher concentration of fumigant, and I would even argue that it’s more effective. In fumigation, I believe time is the most critical component and is often in short supply. Where concentrations of fumigant may be low or temperatures are less than ideal, time can be added to increase the treatment’s effectiveness. Increased exposure time allows fumigants to reach farther into a structural void or penetrate a commodity in storage where the insects and their eggs are found. Insect species, facility or commodity temperatures, and time allotted for exposure are the primary guidelines to prescribe the right fumigation. When looking at options to resolve stored product pest issues with a fumigation, consider how Time and Temperature can help you improve your results and make hay while the sun is shining