Finding herbicide deals before winter to help reduce potential supply chain issues next spring may be wise and may also save you money. But it requires having the proper storage to maintain shelf life and product efficacy.
“If the herbicide input buy is a good deal and you have a safe storage area that can keep products from freezing, it makes great economic sense,” says Dwight Lingenfelter, Penn State University weed scientist. “The best advice is to work with your ag retailer to discuss these issues.”
When storing a variety of liquid herbicides, it’s best to determine temperature restrictions for individual pesticides because they can vary significantly between products. “Each product should stipulate specific parameters on the chemical label under the “Storage and Disposal” section,” he says. “Some labels provide scant info while others provide good details about temperature ranges and what to do if the product freezes.”
Lingenfelter says a good rule of thumb is to store pesticides between 40- and 90-degrees F. Also, pay attention to liquid products with multiple active ingredients as these premixes seem to be affected more by lower temperatures than single active ingredient products. Container size also comes into play, as 2.5-gallon jugs will reach a frozen state quicker than 200-gallon bulk totes.
For example, glyphosate must be stored no colder than 10 degrees F, but glufosinate needs to stay above 32 degrees F. Generic products also vary due to different inert ingredients with varying freezing points. Examine product labels by visiting the CDMS search engine.
“It’s a good idea to check products throughout the winter, check for cracks and even shake the containers or hook up a battery to a bulk tank to agitate and resuspend the content occasionally,” Lingenfelter says. “Some products, like certain 2,4-D formulations, may freeze, causing active and inert ingredients to separate during winter. But if you let them warm back up naturally in the spring, you can roll and shake the container to resuspend the contents without losing product efficacy.”
Depending on storage conditions, the shelf life of crop protection chemicals is difficult to predict. Most chemical manufacturers recommend storing pesticides no longer than two to three years; some labels state storage life ends once the container is opened. If you can't find this information on the product label, check with your ag retailer or the technical representative from the chemical company.
Pesticide manufacturers invest millions of dollars in formulation and packaging research and development, along with rigorous testing of all products in compliance with EPA and FIFRA guidelines to develop stable formulations. In addition, storage tests are done in extreme heat and cold conditions to determine if products return to their original form.
Water-based formulations like suspension concentrates (SC) and suspoemulations (SE) are subject to water crystals forming in cold conditions and then melting when temperatures warm up. If soluble liquids (SL) and emulsifiable concentrates (EC) freeze, active ingredients can crystalize and precipitate out of the solution. When this happens, the crystals must redissolve when warming back up. If crystals remain in EC products, this jug shouldn’t be used as it will cause spray mixing and nozzle clogging problems.
Product viscosity of liquid pesticide formulations is also a critical property to maintain for easy handling and mixing, especially in bulk tank storage where rapid pumping is required. Take similar care to keep particle size in formulations with suspended solids. Excellent details on all these factors are available in the booklet “Is This Pesticide On My Shelf Still Good” from Purdue University Extension.
Product integrity and efficacy are paramount, so follow storage restrictions closely. “No one wants to invest a lot of money in herbicides, then realize next spring that poor storage led to separated products that plugged the sprayer and caused a day of downtime for cleanout,” Lingenfelter says.
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