Pesticide Shelf Life

Pesticides in general are manufactured, formulated, and packaged to specific standards. However, when stored improperly, they can break down, especially under conditions of high temperature and humidity.
Dry formulations such as wettable powders (WP), soluble powders (SP), water-dispersible granules (WDG), and granular (G) can become caked and compacted. Emulsifiable concentrates (EC) can lose their ability to form emulsions. Some pesticides can actually become more toxic, flammable, or explosive as they break down.
Pesticide formulations that contain low concentrations of active ingredients generally lose effectiveness faster than more concentrated forms. Sometimes a liquid pesticide develops a gas as it deteriorates, making opening and handling containers quite hazardous. Certain pesticides have a characteristic odor. A strong odor in the storage area may indicate a leak, a spill, or an improperly sealed container.
It may also be a clue that the pesticide is deteriorating, because the smell of some chemicals intensifies as they break down. If none of these problems is found, chemical odors can be reduced with exhaust fans or by lowering the temperature of the storage area. Pesticide containers, including fiber and metal drums, pails, cans, bottles, bags, boxes, over-packs, and liners, have an important effect on storage and shelf life. If stored for long periods, these containers may eventually corrode, crack, break, tear, or fail to seal properly. The label may become illegible as well.
If a pesticide container needs to be replaced, transfer the pesticide to another container of the same type, such as a polyethylene jug, a thick paper bag, or a brown glass bottle. With plastic jugs, try to find a jug made of the same type of plastic. You can at least get a jug from the same group of plastics by checking the recycling number on the bottom of the jug and using a replacement jug with the same number. Obtain a replacement label from your pesticide dealer to put on the new container.
If stored in a cool, dry area that is out of direct sunlight, pesticides will generally have an extended shelf life. Protection from temperature extremes is important because heat or cold can shorten a pesticide's shelf life. At temperatures below freezing, some liquid formulations separate into their various components and lose their effectiveness. High temperatures cause many pesticides to volatize or break down more rapidly. Extreme heat may also cause glass bottles to break or explode.
One way to ensure that you avoid problems with shelf life or storage is to only buy what is needed for one season. Buying more pesticide than is necessary because of reduced case lot prices or a sale may become more expensive in the long run, when it comes to disposing of excess pesticide.
Before storing chemicals, read the label and follow any specific guidelines listed. Store different groups of pesticides, such as herbicides, insecticides, and fungicides, in separate locations in the storage area. This will help prevent cross-contamination from fumes and vapors as well as accidental use of the wrong type of pesticide. Never store chemicals near any type of animal feed. Always store chemicals out of the reach of children, preferably in a locked cabinet or room in which only pesticides are stored. Store personal protective equipment, such as gloves, goggles, aprons, and respirators, in another clean, dry location away from pesticide fumes.