If pesticides froze over the winter, a review of the labels is a good starting point to determine what may be damaged. Garo Goodrow photo.
On the farm there are many demands of time and sometimes things that you wanted to do do not get completed. For example, you may have left some pesticides in an unheated building over the winter and are wondering if that was a costly mistake.
The normal temperature range recommended for storing liquid pesticides is usually 40° to 100° Fahrenheit. Some pesticide labels state a specific temperature range for maintaining optimal storage shelf life. As a rule, wettable powders and granules are not affected by low temperatures. Before storing pesticides, the applicator needs to read the "storage and disposal" section of the pesticide label.
Examples of Pesticide Storage Temperature Guidelines:
2,4-D Amine: The label says, “Store at temperatures above 32°F. If allowed to freeze warm to 40 degrees and remixed thoroughly before using. This does not alter this product.”
2,4-D LV4: The label makes no mention of storage temperature minimums or maximums.
Atrazine 4L: The label makes no mention of storage temperature minimums or maximums.
Banvel: The label makes no mention of storage temperature minimums or maximums.
Engenia: freezes around 15°F and is stable under conditions of freezing and thawing. Product that has been frozen should be thawed and recirculated prior to use.
FeXapan: The label makes no mention of storage temperature minimums or maximums.
GlyStar Plus: Store above 10°F to keep the product from crystallizing. Crystals will settle to the bottom. If allowed to crystallize, place in a warm room 68°F for several days to redissolve and roll or shake container or recirculate in mini-bulk or bulk container to mix well before using.
Lumax EZ: The label says can be stored at temperatures as low at -10°F
Gramoxzone SL: Store at temperatures above 32°F
Touchdown Total: The label makes no mention of storage temperature minimums or maximums.
Warrior II: The label states “Do not allow product to freeze.”
Roundup PowerMax: The label makes no mention of storage temperature minimums or maximums.
When a liquid pesticide freezes, the active ingredients can separate from the solvents or emulsifiers, causing the emulsifiers to become inactive, crystalize and coagulate, breaking down the original product. If frozen, some pesticides can be thawed naturally at room temperature, but never use a flame or heat. Also, make sure the container has not cracked. After thawing, roll and shake the container to re-suspend the contents. If crystals are still present after thawing, the pesticide should not be used as it will be ineffective. Rather, properly dispose of it according to label directions.
For additional information check out Winter Pesticide Storage from the University of Nebraska-Lincoln and Temperature Effects on Storage of Agricultural Pesticides from the University of Missouri Extension.