Handling leftover crop protection chemicals

Storing unused herbicides, insecticides and fungicides after the spraying season requires careful attention to handling and storage conditions.

The main goal is to prevent products from freezing and maintain effectiveness. Chemical manufacturers test products and packaging to ensure two to three years of physical stability under a range of storage conditions, as required by the U.S. Environmental Protection Agency (EPA) as part of the federal registration process.

Temperature extremes, particularly below 32 F, can reduce product effectiveness and damage pesticide containers over time, said Fred Whitford, director of Purdue Pesticide Programs at Purdue University.

“Some product labels state simply that a product freezes at 32 degrees; others may say it freezes at 32 degrees and should be warmed up and shaken,” Whitford said. “But most labels don’t address whether the freezing-and-thawing process will affect how well the product works.”

Judging shelf products

It’s common for farms to have herbicide containers left over from previous years. Whitford frequently hears farmers ask, “Is this stuff still good?” It’s an important economic question, because those containers represent money sitting on the shelf.

Those conversations led to his involvement in the Purdue Extension booklet Is This Pesticide on My Shelf Still Good? It’s a great resource for understanding the details on how to evaluate and track chemical inventory.

Whitford typically responds to questions about product integrity with questions of his own: “Was it stored properly? Was the container ever opened? Do you know how old it is? If it’s a dry product, has moisture caused it to clump or harden? Is it still a federally and state-registered product?”

If too many of those questions can’t be answered or the answers raise concerns, a better inventory management process may be needed. If the product is still sealed and less than 3 years old, odds are it is still good as new, Whitford said.

For older chemicals, especially products that have been opened, determining whether a product remains effective becomes more challenging.

Many formulations, including active and inert ingredients, can remain effective for a long time when stored in a temperature-controlled environment. However, no product remains permanently stable. Packaged premix herbicides require additional attention, because multiple active ingredients can degrade at different rates.

To evaluate the physical stability of a leftover jug, perform a jar test. If the product appears stable, mix a small batch in a hand-held sprayer and apply it to labeled weeds to evaluate herbicidal activity.

“If you’ve got a larger quantity in inventory, call your local sales or technical representative from the company that makes the product,” Whitford said. “They will, hopefully, call their chemists to determine possible product integrity.”

They may ask for the EPA registration number and lot number on the packaging.

Storage guidelines

While storing products with an ag retailer is often the safest option, growers can create a suitable on-farm storage space by following a few key guidelines.

“If you take advantage of herbicide discounts in the fall, ask the ag retailer to store the products until spring because their facilities are usually better equipped for possible emergencies in a temperature-controlled environment,” Whitford said.

Winter is a good time to update your product inventory, review storage instructions on product labels and organize storage areas to reduce potential hazards associated with improper storage.

Log the weights of liquid and dry products in an inventory log or spreadsheet, along with a map showing storage locations on the farm. This information can be valuable during a fire or other emergency.

Ideal storage areas are locked, clearly labeled and separated from equipment, fuels, oils and other farm activities. Write purchase dates on 2.5-gallon jugs and place them in plastic containment tubs to catch potential leaks. Store older products toward the front so they are used first. Seal open granular bags with tape and place them in plastic bags to keep moisture out.

Chemical disposal

To dispose of old or unwanted products, many states offer pesticide collection programs. The Pesticide Stewardship Alliance promotes full life-cycle stewardship through pesticide container recycling programs and by connecting users with licensed hazardous-waste contractors for disposal of unwanted chemicals. Check out the map and click on your state to locate a vendor.

“While farm chemical storage may not be a top priority among farmers, it is so important for financial, environmental, insurance and many other reasons,” Whitford said. “You’re going to save yourself a lot of trouble and a lot of money for the time you’re going to spend storing products properly, while letting others be informed about what’s around your farm.”