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Shelf Life of Pesticides

Pesticides left over after the garden season can pose a storage problem. Safety is of course, a concern and all pesticides should be stored out of the reach of children and under lock and key if possible.

Since many home gardeners may use only small quantities of a chemical in any given season, the question often arises. How long can I keep my chemicals before they lose their effectiveness. A study of information by chemical manufacturers by J. Capizzi provides information on ranges of shelf life for pesticides.

All companies contacted in the study recommended not storing pesticides longer than two years. Other recommendations are to keep temperatures below 100 degrees F. And do not allow liquids to freeze. Keep chemicals in original containers and tightly sealed. The following are estimates on the shelf life of various insecticides, fungicides, and herbicides.

                     Shelf life
Pesticide             (years)                Comments
--------------------------------------------------------------------------------
Sevin, wp              several               flowables will settle
Diazinon                5-7
Disyston                 2
Malathion, wp          indefinite            decomposes under high temperatures
Metasystox-r             2
Methoxychlor, wp       indefinite
Imidan, wp              2-3
Benlate, wp              2                   keep dry
Captan, wp               3
Thiram, wp               4                   keep dry, below 100 degrees f.
Ammate, sol. Salt      at least 2            no low temperature limit
Casoron, 4g            at least 2
Dacthal, wp            at least 2
Roundup, liquid        at least 2            stable below 140 degrees f.,
                                             Do not freeze
Kerb, wp               at least 2
Paraquat, liquid       indefinite            very stable, do not freeze
Princip, wp            indefinite
Surflan, wp              3
Treflan, g               3                    loss 15 -20 % activity
                                              when stored at 100 degres f.

It is also important to regularly check stored pesticides, especially if you have stored them for more than a year. Some pesticides, if stored improperly or for too long a time, will not mix properly and may be ineffective. Watch for the following indications that your pesticides should be properly disposed of:

Formulation                         Signs of breakdown
-----------------------------------------------------------------------
oil sprays                  sludge forms, solution separates
emulsifiable conc.          Addition of water does not produce a milky
                            solution
wettable powders            lumping, powder will not mix with water
dusts and granules          excessive lumping
aerosols                    generally effective until nozzle clogs or
                            propellent is dissipated

The folowing are some suggestions for safe storage:

1. Be sure that caps are tightened securely on all bottles and cans. Eliminate leaky containers.
2. Do not store weed killers close to other materials such as wettable powders, dust formulations or granular insecticides. Some weed killers such as 2,4-d and 2,4,5-t are highly volatile substances and can contaminate other materials especially when confined in close quarters.
3. Store wettable powders, dusts and granules of pesticide products in a cool, dry place.
4. Do not store liquid pesticides in a place where the temperature will fall below 40 degres f. Too low temperature may result in a breakdown of liquid material, and if the liquid should freeze, there is the danger that the glass containers will break.
5. Do not carry over pesticide products whose labels have been lost or are not complete and legible.
6. Above all, keep pesticide materials in a locked room or cabinet and out of reach of children and animals.
7. Glass bottles should always be stored within a metal can, not necessarily closeable, such as a coffee can. In the event the bottle breaks, the spillage will be contained.
8. Always purchase pesticides in a container size small enough to be used up within a season or less. This is the best method for reducing storage problems. Although this method may seem somewhat uneconomical, in the long run, it may prove to be a great savings when one looks at the previous six suggestions.

Source: J. Capizzi, OPEW (Vol. XI, No. 3)

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For more information relative to pesticides and their use, please contact the PMEP staff at: Pesticide Safety Education Pgm. 5123 Comstock Hall Cornell University Ithaca, NY 14853-0901 (607) 255-1866 Pesticide Sales & Use Reporting Database Grp. Cornell University 20 Thornwood Dr. #106 Ithaca, NY 14850 (607) 257-5706

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