Pesticide Shelf Life
Shelf or storage life of pesticides is difficult to predict and is dependent on storage conditions. Most chemicals manufacturers recommend storing pesticides no longer than two years. Most will not guarantee their products any longer than that. A few labels will indicate the storage life of the pesticide once the container is opened, but most do not.
Pesticides are manufactured, formulated and packaged to specific standards. However, when stored improperly, they can break down especially under conditions of high temperature and humidity. Some pesticides can lose their active ingredients through chemical decomposition or volatilization. Dry formulations (wettable powder) and become caked and compacted under conditions of high temperature and humidity; emulsifiable concentrates (EC s) can lose their ability to form emulsions. Some pesticides become more toxic, flammable or explosive as they break down.
Pesticide formulations with low concentrations of active ingredients generally lose effectiveness faster than more concentrated forms. Sometimes a liquid pesticide develops gas as it deteriorates, making opening and handling containers quite hazardous. In time, the gas pressure may cause the container to rupture or explode. Certain pesticides have a characteristic odor. A strong odor in the storage area may indicate a leak, spill or 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 are found, chemical odors can be reduced by installing an exhaust fan or lowering the temperature of the storage area.
The following pesticide product characteristics affect shelf life:
- the formulation (liquid concentrate, wettable powder, granules)
- the types of stabilizers and emulsifiers used in the product.
- the chemical nature and stability of the product.
- the type of container and its closure.
Pesticide containers 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. Also, the label may become illegible. If a damaged container is found, transfer its contents to a similar sturdy container that can be sealed. Be sure to transfer the label to the new container. Never put a pesticide in a food or drink container!
Make certain the lids on containers are tightly closed. Seal open bags or containers of dry formulations of products.
To reduce the problem of having old or ineffective pesticides, try to purchase only the amount of pesticide needed for the season. If possible return unused, unopened containers to the dealer. If it is necessary to maintain a larger inventory, be sure to rotate the stock. Older pesticides should be used first. Tag or mark pesticide containers upon delivery with the date of purchase. To keep the label on a container intact and legible, cover it with transparent tape or lacquer.
To help maintain the shelf life of stored pesticides, store them out of direct sunlight and keep them dry. Protect from excessive and temperature extremes.