Seed Facility Fumigation

7/2022 Issue: Seed Facility Fumigation

By: Pete Mueller

The production of seed is a unique process that requires a unique approach to pest management. One not directly involved in agriculture would be forgiven for underestimating the technological genius that is required to make the perfect uniform rows of corn, soybeans, and wheat that checkerboards the Midwestern landscape. Seed is selectively bred and biologically engineered not only for the highest yield but for traits like disease and insect resistance, drought tolerance, plant uniformity and so much more.

As a practice unplanted seed is returned to seed production facilities to be reprocessed. In doing so often rodents and stored product insects are introduced into these processing facilities and connected warehouses. This practice inadvertently exposes unaffected product to an onslaught of pest pressure. One bag of seed can range in cost from $50 for soybeans to $500+ for the latest varieties of seed corn. Each bag of seed can produce up to 80,000 plants, yielding around 300 bushels of harvested corn per acre. With the amount of returned product from farms across the country, a facility can quickly exceed controllable pest thresholds in a matter of just a few days.

This is not to say that conventional pest management practices do not slow down pest damage to the product and in some cases to the facility as well. When seed has been returned to the facility the best way to reduce the now resident pest populations to as close to zero as possible is with the use of a fumigant. A fumigant is a pesticide that reaches the targeted pest in the form of a gas. One benefit of fumigants is that they leave no residue, they are great at penetrating pallets of product, bags, boxes, and structures.  They also work quickly and are effective on a wide variety of pests. A fumigation is a balance of applying the correct concentration, for the right amount of time and at a given temperature to kill the target pest. The partnership between conventional pest management practices and fumigation treatments is critical to the success of a seed facility pest management program. Information like the size and scope of the affected area and the target pest itself can be the difference between success and failure where pests will rebound quickly.

There are two families of chemistry that are commonly selected for fumigants both domestically and abroad. These fumigants, in addition to the benefits do not affect the germination of seed at normal recommended dosage rates. First, and most commonly throughout the world is Phosphine (PH3). Produced in many different formulations, Phosphine gas has long been the go-to fumigant for treatments like this. To target rodents with Phosphine the typical rule is 100 ppm for 24 hours will be successful.  Whereas 300 ppm at 78 Fahrenheit(25C) for 36 hours will control all life stages of Indian Meal Moths (the most common stored product insects faced in seed production facilities). The main drawback to Phosphine is that it is corrosive to soft metals and electronics. Also, the mode of action targeting the energy producing portions of the cells means longer exposure times may be necessary. In the US, sulfuryl fluoride (SO2F) under the trade name ProFume is often a better fit for seed facility fumigations.  This is due in part to ProFume’s noncorrosive properties, and the ability to prescribe to the target species the correct dosage by using the interactive Fumiguide.  A software program that considers all the variables and helps the fumigator ensure success. For comparison, ProFume requires a 36 CT (concentration over time). And Indian Meal Moth require a 350 CT in a typical treatment lasting 24 hours. This allows for the reduction of downtime and the necessary removal of electronics as is required for Phosphine fumigations.

The fumigation treatments lack of residual is both a benefit and a draw back. After the fumigation treatment is completed the pest management program will not have any control on the post treatment introduction of pest. A DynamicIPM program will continue to monitor for reintroduction of pests and prolong the benefits that a successful fumigation brings to a pest management program.  A quality monitoring program will sustain quality long after the fumigation process is completed.