Pesticide Shelf Life
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:
- Be sure that caps are tightened securely on all bottles and cans. Eliminate
leaky containers.
- 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.
- Store wettable powders, dusts and granules of pesticide products in a cool, dry
place.
- 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.
- Do not carry over pesticide products whose labels have been lost or are not
complete and legible.
- Above all, keep pesticide materials in a locked room or cabinet and out of reach
of children and animals.
- 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.
- 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)