Introduction

Storage temperature influences the effectiveness and usability of many pesticides. Most labels of liquid pesticides contain specific information on adequate storage temperatures for their products and will generally state a temperature in the 40°F–100°F range. Freezing is not a normal concern for pesticide storage in Florida, but extreme heat is a factor for the entire state.

Freezing temperatures can render a liquid-formulated pesticide useless by causing the active ingredients to separate from the solvents, emulsifiers, and other inert ingredients. The result may be either crystallization or coagulation of the formulation. Some products may be thawed and reused after adequate agitation; their labels will specifically state if this is the case. Because of the ingredients in the formulation, the freezing point of many products may be lower than 32°F.

Heat is the major concern in Florida for pesticide storage problems. Heat can cause some pesticides to volatilize and drift from their containers, especially if containers are not adequately sealed. Flammability is a problem with some pesticides in the presence of heat and/or open flame. For more on this topic, see EDIS publication PI-97 Pesticide Labeling: Physical or Chemical Hazards (https://edis.ifas.ufl.edu/pi134).

Containers may be damaged by either temperature extreme. Freezing temperatures can cause containers made of glass, metal, or plastic to break. Alternatively, high temperatures can cause plastic containers to melt and glass to explode. Liquid pesticide contents stored in metal drums can expand and eventually rupture (Figure 1).

Generally, dry pesticide formulations are not adversely affected by temperature extremes. Their effectiveness is most often reduced by the presence of moisture in storage. These products have a high affinity for water and, once absorbed, may solidify into hard masses (tombstone formation). The packaging that surrounds dry products formulated as water-soluble packets can become brittle after taking on moisture; and if freezing occurs, they can break when handled.

To learn storage temperature limitations for individual products, consult the "Storage and Disposal" section of the pesticide label (Figure 2). Many products will have specific temperature limitations mentioned in this section; others may be more general. If you have questions regarding these limitations, consult the product's manufacturer.

General information on storage and disposal language found on pesticide labels is discussed in EDIS publication PI-106 Pesticide Labeling: Storage and Disposal (https://edis.ifas.ufl.edu/pi143).

Table 1 lists many commonly used agricultural herbicides registered for Florida. They are listed alphabetically by active ingredient common names (center column) with their trade names and any storage limitation statements from the Storage and Disposal directions. Not every herbicide common active ingredient and/or their associated trade products list storage limitations on the storage statements.

Additional Information

Fishel, F.M. 2012. Pesticide Labeling: Physical or Chemical Hazards. PI-97. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/pi134

Fishel, F.M. 2012. Pesticide Labeling: Storage and Disposal. PI-106. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/pi143

Tables