Early Grain Fumigations

March 2025 Issue:

By: Levi Farrell, A.C.E.

A winter season has come and went that allowed you to cool your grain down to temperatures not conducive to insect activity. Spring is now here, and the headspace begins to warm. The merchandisers tell you it’s time to ship. Low and behold, you start seeing insects in your samples.

Temperature and quality are the keys to any successful fumigation. Exposure periods should always be based off the lowest temperature. Several other factors also need to come into play with carried grain. Was the bin cored properly to allow uniform airflow throughout the mass? Did the front get pushed throughout the bin? Are there any hot spots or crusty areas that have formed? Was this a wet bin that you did not get dried down or a high damage bin? These are all things that should be reviewed prior to beginning the fumigation.

Although label states you can treat down to 40 degrees(4C), the exposure period required to achieve control at this temperature is 14 days. Most of the time this is not feasible or realistic based on customer demands and delivery deadlines. It is critical that the proper amount of time is given to allow the treatment to be successful. Phosphine must build in the insect’s body to lethal levels. This is the reason for the correlation between exposure period and temperature. Studies have found that immobilization can occur, but at levels too high or too low, insects can recover days after the treatment has been completed. Latent mortality is also a condition that can be possible. Due to the reduced respiration during diapause, insects can intake a lethal dose, but not enough to be immediately toxic. Movement will be slow, and the insect will eventually expire hours or days after exposure.

The final step is preparation of the structure. Weather in the spring is typically unpredictable and can be violent. Proper preparation to maintain gas concentration is crucial, especially during treatments requiring extended exposure periods. Recirculation of the fumigant, along with efficacy readings to ensure lethal concentrations are present throughout the exposure period is required. Efficacy readings, along with bystander safety readings are a requirement of the label.

Temperature and exposure must be altered together. You cannot decrease one without increasing the other. Preparation must be meticulous and methodical. Know your concentration, don’t assume just because you went at a high rate, lethal concentrations were achieved and maintained.

Happy fumigating everyone and remember to calibrate those monitors!!!