Photograph of man

Wyoming tale cautionary note about storing, using old pesticides

The 80-something Wyoming man walked into his house and his wife asked, “Why are you naked?”

Warmish, June temperatures had nothing to do with the answer, but the explanation is the take-away message University of Wyoming Extension pesticide safety education program coordinator Jeff Edwards wants to get out to those applying pesticides.

Don’t use, and please properly dispose of, old pesticides that have been in sheds and garages for a long time, and using those removed from the market is not recommended. Or you, too, could have your significant other asking about your wardrobe choice.

Man in hat standing in front of camera
Extension pesticide safety education coordinator Jeff Edwards

Pesticides don’t have an expiration date, but there are reasons not to use products in storage for a long time or have been pulled from the marketplace, said Edwards.

The beginning to the wife’s question actually started last year, when Edwards and those in various weed and pest districts noticed grasshopper numbers building.

“I would say there were some outbreaks last year that were indicators of what was coming this year,” Edwards said. “So (weed and pest control districts) have been preparing, but it’s a little more widespread than what I think the general public was prepared for.”

The treatment window, when the hoppers are smaller, most susceptible and applications most effective, is closing fast, Edwards said.

Edwards suggested those choosing to apply pesticides use the reduced area agent treatment process pioneered by the University of Wyoming Extension – applying the product in alternating strips to take advantage of grasshopper movements and to use less chemical.

Grasshopper identification and management publications from the University of Wyoming Extension are available. A website with many grasshopper information resources is at Rangeland Grasshopper Management is here A Field Guide to Western Grasshoppers is at Common Wyoming Pest Grasshoppers is here The Pest Grasshopper of the West – Identification and Management Poster is available at

The higher hopper numbers had people searching through their storage units and bringing out older products used years earlier.

“There are some old standbys still available, but if you haven’t stored your products correctly, those older chemicals that have been in storage may not have the efficacy we are looking for to control grasshoppers,” Edwards said.

Chemicals should be kept in a Goldilocks environment – not too hot, not too cold.

If there is a product you haven’t used for a number of years and if the solution has settled out and you can’t shake it into solution, “Then get rid of it,” said Edwards. “If you use an older product and it seems to not work like it used to, it’s time to get rid of the product.”

Edwards isn’t immune. He retrieved a product he hadn’t used in a while and despite all the shaking of the container, the “clump” at the bottom wouldn’t go back into the solution.  One way to keep track of the age of your pesticide inventory is to write the date of purchase on the outside of the package with a permanent marker.

He suggested that pesticides you are unsure of be taken to toxic waste collection days; there are certain weed and pest control districts in the state that have toxic waste collection days, usually in the fall.  Edwards recommend contacting them to find out if your local district offers this.

Some products are no longer effective, depending upon the shelf time. Malathion, for example, has a shelf life of three to five years regardless of how its stored, Edwards said. He has seen studies that show Malathion breaks down into products more toxic than the original. Other products can break down into chemicals that are non-toxic and have no effects.

The 80-ish Wyoming man had a product he had used for grasshopper control years ago and due to new safety standards had been pulled from the market. He used the chemical last year and said he had not felt well after its application and wasn’t quite sure where he was.

But he picked up the same product and used it this year. Using products removed from the market is not illegal, “But there are reasons why these older products have been pulled from the marketplace because the safety standards have been improved,” said Edwards.

“The fumes apparently affected him, and he walked into his garage, stripped off all his clothing, and went into his house,” he said. The man couldn’t remember where he was or what had happened.

“Thankfully, he recovered,” said Edwards. “You really have to be cautious when using products that have been maybe a little too long in storage.”

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