Plant Pathology Infobytes
February 25, 1999
Are Your Fungicides Safe for Spring Use?
Warm, sunny days this time of the year crank up most gardeners' desire to kick off the spring season. While it's generally safe over most of the state for planting cabbage, Irish potatoes, English peas, and other cool season vegetables, other crops are risky, since it's likely Old Man Winter has a few more days in reserve.
There are gardening projects which should be standard chores when those cool, wet days make their appearance which will increase chances of production success when the spring gardening season arrives to stay. For example, now's a great time to inventory your supply of carryover pesticides from last gardening season.
Many gardeners have questions concerning the use of fungicides, insecticides, and other pesticides which were stored away last fall -- are these products still good, and will they effectively control pests which attack vegetables, orchard crops, turf, and ornamental plants in the home landscape?
Since pesticides often represent a significant part of a gardening budget, this is a good question. Obviously, if you're going to spray, it's a good idea to be assured the spray mixture is going to be effective for those disease and insect problems which appear each season. While the following guidelines relate primarily to fungicides, they are also applicable to most other carryover pesticides in the storeroom.
Many leftover fungicides may be used the second year if they have been stored properly in an area protected from freezing temperatures during the winter and high temperatures during the summer. Homeowners should carefully examine any leftover pesticide containers for leaks, cracks, tears, worn areas, seal failures, and bulges. Bulges on a metal container may be a sign of gas development which can make handling or opening the container hazardous.
The presence of a strong odor indicates an improperly sealed container, a leak, or possibly a spill. When there are doubts concerning effectiveness, age, and condition of a fungicide after long term storage, test for deterioration.
Signs of deterioration observed with various formulations of pesticide include the following:
- Wettable powders - excess lumping occurs and the powder will not suspend in water.
- Emulsifiable concentrates - milky coloration fails to occur when water is added; sometimes a "sludge" occurs which may indicate separation of pesticide components.
- Flowable type fungicides - will not properly mix and it is almost impossible to get the sediment in the bottom of the mixing container back into suspension.
If any of these signs are detected as you prepare fungicide or insecticide mixes for disease and insect control, the best advice is "don't take a chance." Not only is it likely that such pesticides are not going to be effective in controlling plant pests, there's a chance that spray mixes prepared from such products will cause severe plant injury.
When fungicides and other pesticides are determined to be unusable, they should be properly disposed of according to local, state, and federal regulations. For information on pesticide disposal, please feel free to check with us at your county Extension office.
Infobytes newsletter was written by the late Dr. Frank Killebrew, Extension Specialist.