Summer is a time of the year when insects can quickly populate into high numbers. Where did all these insects come from? In a warm, moist environment, the fly cycle of egg to larva (maggot) to pupa to adult can take about a week. A micro-environment, such as a small trash container, can create 1,000 flies in one week. Stored product insects, such as flour beetles in ideal conditions, can produce high numbers in might take three to four weeks.
Managing insects with temperature is an effective, environmentally sensitive approach. What is the impact of moisture? What temperature parameters are needed to manage insects? What are some practical solutions?
MOISTURE. How important is moisture? Life requires moisture for sustainability. Keeping a food plant dry is critical in managing insects and microbes. If you control moisture in the food plant, you can minimize the impact of insects and microbes. This includes managing the drying activity following any wet cleaning along with humidity, condensation, and other sources of moisture.
TEMPERATURE. According to research conducted in the 1990s by Centre Agriculture and Agri Food Canada Research Scientist Paul Fields and subsequent research by Kansas State University Professor Bhadriraju Subramanyam, insects will respond differently to different temperatures. Although manipulating an environment with temperature has been recognized as an effective insect control method for many years, the subject has not received much attention lately.
The optimum temperature for maximum insect development is 75°-90°F; if magnified by moisture, microbial growth can be accelerated. One approach for managing insects is to create an environment outside this optimum temperature zone of survival and reproduction:
- 120°-140°F: insects die in minutes. Much has been written about heat treatment for insect control in equipment, plant zones, or entire buildings. Knowledge and expertise are needed to ensure the hot air reaches the insects before they escape, as insects will rapidly move away from high heat.
- 110°-115°F: insects will die within hours. This temperature range can be found in a few areas of a food plant operation. Don’t be concerned about insect development in these areas. This temperature can be used to store insect-sensitive material such as pallets, sieve screens, or filter socks. You can use this area to disinfest small equipment and/or materials.
- 95°-100°F: insect development stops. This temperature range is found in some areas of a food plant, especially grain handling and processing operations. One advantage of a high-temperature environment is that insects will not develop into a population problem.
- 65°-70°F: insect development slows and insects are somewhat repelled. Insects will leave this temperature in pursuit of a warmer temperature. Storing insect-sensitive ingredients or finished products in this cooler range is an effective approach.
- 55°-60° F: insect development stops. Grain cooling has been used for years to prevent insect activity and extend grain shelf life.
- 35°-45°F: insects die in weeks. The cooler side of this temperature range is a suggested range for food refrigeration. Don’t be concerned about insect development in these areas. Not all food plant operations have such cool zones, but these areas can be used to store insect- and temperature-sensitive materials to protect them and extend shelf life. Shipping food products in refrigerated containers should become more popular with time.
- 10°-20°F: insects die in minutes. These temperatures are used for food freezer storage. Stored product insects do not survive a quick hard freeze.
Similar to guidelines to maintain foods at temperatures below 40°F and above 140°F to prevent bacteria growth, temperatures below 75°F and above 90°F can be used to manage insects in food plants. If your food plant’s temperature is within an insect’s desired range, you are likely to need to spend resources on exclusion, sanitation, and pest control activities. In some plant areas, a temperature adjustment slightly downward or upward is a practical solution. In addition, keeping the plant dry will lower risks associated with insect and/or microbial activity while providing a safer overall environment. Be cool, be dry, and be hot (at key times) to manage insects with temperature.
Insect Management for Food Storage and Processing, Second Edition, edited by Jerry Heaps, Chapter 10 - Temperature Modification for Insect Control, Ole Dosland, lead author. (AACC International, 2006).