CITY OF MANSFIELD STORM WATER MANAGEMENT
PESTICIDES
What Are Pesticides?
A chemical substance used to kill pests, especially insects.
What Are Herbicides?
A chemical substance used to destroy or inhibit the growth of plants, especially weeds.
How Do Pesticides And Herbicides Work?
The answer to this question depends entirely on the type of substance used. In general, the substances inhibit some function of the nuisance organism so that the organism dies or cannot reproduce. This can be blocking nerve transmission, water intake, oxygen exchange, photosynthesis, or any other process that is necessary for the organism to survive or reproduce.
One problem with pesticides and herbicides is that what works for one organism will likely work for many others. A poison applied to kill rats and mice will often kill dogs, cats, and people as well. The USGS has prepared this list of FAQs about pesticides.
How Do Pesticides And Herbicides Enter Our Waterways?
Rarely, these substances are actually poured down storm drains. More often, these substances are washed off the areas where they were applied (either by excess irrigation or rainfall) and into the storm drain system. These substances are then transported down into our creeks, streams, ponds and lakes. Another route of entry is actual application in and around our local waterways.
Pesticides and herbicides can be classified by the amount of time they can be expected to remain in the environment. Persistent compounds remain in the environment, relatively unchanged, for very long periods of time. An example is Chlordane, a chemical used to control termites, which was banned from use and production in 1988. Fish tissue samples taken in 2002 in the Upper, West and Clear Forks of the Trinity River, and several lakes in the area contain significant levels of the compound.
Typically, a non-persistent substance does not remain in the environment unaltered much longer than one week. But they pose no less of a risk in the short time they are present.
How Can I Keep Pesticides And Herbicides Out Of The Local Waterways?
Like other issues with pesticides and herbicides there is no easy answer for this question. It is possible to use biological controls, natural predators, for some pests. Ladybugs will remove aphids from roses for instance. Well-maintained lawns will naturally inhibit most weed growth. Diatomaceous earth will help against fire ants.
Many pesticides and herbicides are derived from natural substances, and it is difficult to decipher those that are natural derivatives and those that are man-made. If using a pesticide or herbicide it best to only use as much as is suggested for mixing, to follow the application directions for how often it should be applied, and to never apply a pesticide or herbicide shortly before a rainfall event, or near a source of water.
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