The Disadvantages of Using a Broad-Spectrum Biocide
A biocide, also known as a pesticide or herbicide, is a chemical or organism that destroys another organism. While a broad-spectrum biocide will kill everything that it's applied to, other biocides don't have the same effect.
For instance, a selective biocide, like a broadleaf weed control product, is formulated to kill only organisms with specific characteristics. A selective biocide is commonly used on grass, killing the broadleaf weeds while leaving the grass unharmed. This is due to the fact that the structure of the grass plants (which are called monocots) and the broadleaf plants (called dicots) are different enough that the chemicals can be synthesized to affect one type of organism and not another.
Why Avoid Using Broad Spectrum Biocides?
There are several reasons why you want to avoid using a broad-spectrum biocide. Over time, the target organism, which is the pest that the biocide is meant to kill, will develop a resistance to the biocide. In fact, overusing a broad-spectrum biocide may result in more resistance across a wider spectrum of problem pests. With antibiotics, this leads to the creation of resilient "superbugs."
In most instances, broad-spectrum biocides are unnecessary. If the problem is widespread, it is best to replace the lawn. However, in a lawn that's not completely overrun with weeds, the area that needs to be treated is usually small and specific. Larger patches of weeds can also be spot treated.
Although a broad-spectrum biocide is commonly used to treat small affected areas, this type of biocide can kill harmful organisms as well as beneficial ones. For example, a broad-spectrum biocide destroys aphids (plant lice); however, it may also kill bees if you use an insecticide that's not specially formulated. Using a broad-spectrum insecticide, which is a type of biocide, can cause more damage than you wanted.
Biocides and Water
Water is the preferred method of travel for organisms and chemicals. Therefore, using a broad-spectrum biocide can kill everything in the water, including good organisms. Since most ecosystems keep themselves in relatively good balance, it may be best to leave the pest or weed problem alone. In fact, using insecticides and herbicides to control the ecosystem may result in an imbalance, causing more harm than good.
Broad-spectrum biocides can also disrupt the natural flow of populations. Webworms are a common lawn problem because the population will naturally increase until it becomes so large that there aren't enough resources for them to withstand. As a result, the population will crash and the webworms may disappear for several years. Some pesticide experts believe that using pesticides (biocides) will lead to a consistent level of pests. However, if you let the populations fend for themselves, you will experience pests for a few years before being completely free of pests.
If you're unsure about what type of biocide to use, you may want to speak with either your local garden center or a professional lawn care company. They can select the biocide that's best suited to treat your lawn problem.