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Add to FavoritesGarden centers carry dozens of herbicides which can be used with deadly efficiency to kill weeds, roots and all. They're easy to use, and while some are costly, they spare the gardener a great deal of labor.
The question is, should they be used? Do they have a place in the average suburban garden? The answer isn't as simple as a quick "yes" or "no." It's important to consider how such chemicals are used and for what purpose. In general, it's best to avoid toxic garden chemicals and rely on environmentally-frie ndly methods of weed and pest control. Let's look at why that is true, and some better ways to control garden weeds. Then we'll discuss situations where herbicide use might be justified.
RISK FACTORS
All toxic garden chemicals carry a certain amount of risk, whether they're manufactured chemicals or organic alternatives. Rotenone and pyrethrin, for example, two natural pesticides extracted from plants, are highly toxic to aquatic life and should never be used around ponds and streams. Even fertilizers have a certain amount of toxicity. Gardeners must develop a habit of reading the warning labels on ALL garden chemicals carefully before buying and before each use and ask, "Do I want this in my garden? What if my kids or pets come in contact with it? What are its effects on wildlife?"
Herbicides in particular do carry certain health risks. Glyphosate, the active ingredient in the commercial herbicide RoundUp, has been linked by the EPA to kidney problems in animals that have been chronically exposed to the chemical (see http://www.epa.gov/I RIS/subst/0057.htm), though the risk of cancer from glyphosate exposure was judged to be very low. Not all researchers agree with the EPA, however. The Institute of Science in Society reported on studies linking glyphosate in general and RoundUp in particular to increased risk of miscarriage (see http://www.i-sis.org .uk/GTARW.php). The results on cancer studies remain unclear, as it was uncertain whether glyphosate only or RoundUp was the substance tested.
Safety recommendations based on these studies often assume that the herbicide is used as directed, that gardeners read the labels carefully - every time the chemical is used. Not all gardeners do this. While farmers must follow certain procedures and keep careful records when applying herbicides and pesticides, home gardeners can apply these products indiscriminately, putting themselves, their neighbors, and neighborhood pets at risk. Many of us know someone down the block who "weeds" regularly by spraying with herbicides - and all to often, "helps" a neighbor without asking by spraying the neighbor's weeds as well.
Even if a gardener reads the label on a canister of herbicide, it may not supply much information about health risks. For example, in spite of the EPA toxicity reports on glyphosate, the warning label on a bottle of RoundUp only lists "Causes moderate eye irritation" as a health risk.
Herbicides can poison the soil food web. In a spoonful of garden soil live millions of friendly bacteria and thousands of helpful fungi and protozoa. These organisms recycle nutrients and condition the soil, benefiting the plants, which in turn benefit the organisms in dozens of ways. Herbicides kill any soil microbes they come in contact with, reducing the fertility of the soil.
Finally, broad-spectrum herbicides can't tell "good" plants from "bad" ones. Whether it's those pesky dandelions or your prize dahlias, anything the herbicide touches will be killed or damaged. Even on a day when the winds are still, it's hard to completely prevent herbicide drift, especially when applying herbicides or weed-and-feed to a lawn through a hose-end sprayer.
ALTERNATIVE METHODS
Herbicides should never be used as a general substitute for hand weeding. Pulling weeds by hand takes time, but its the least expensive method with the least impact on the garden environment. Garden centers carry many tools to make the job of weeding easier: hoes, scuffle hoes, stirrup hoes, claw-like weed pullers, and more. Time spent on your knees among your plants also increased the likelihood that you'll spot diseases or insect pests before they get out of hand.
For gravel and paved areas, where weeds creep through the cracks and are hard to pull, vinegar, boiling water, or a propane-powered weed flamer will usually kill them. Be cautious with the weed flamer, and don't use it on any flammable surface, including mulched areas. These methods usually kill the top of the plant but not the roots, so repeat applications may be necessary.
Mulch is a great weed preventative. Some gardeners lay down black plastic first, but this smothers the soil underneath and renders it infertile. Landscape fabrics are a little better, but better still is to remove all weeds and sprinkle the soil with an organic pre-emergent weed control such as corn gluten before spreading the mulch. This will prevent seeds beneath the mulch from germinating. Mulch supports an active soil community and slowly fertilizes plants as it decays.
Corn gluten can be used in gravel areas as well as mulched areas for controlling weed growth. It's a pre-emergent, so it won't kill weeds that are already growing. It needs to be applied frequently throughout the growing season, as its effects are cumulative. Don't apply corn gluten to your vegetable garden, a newly-seeded lawn, or any other place where you're growing plants from seeds, since it will prevent your seeds from sprouting.
WHEN TO USE HERBICIDES
If you're dealing with noxious or invasive weeds, killing them roots and all with an herbicide may be justified. Poison oak, poison ivy, and other harmful invaders can be removed permanently by spraying the plants first, letting them die completely, then pulling them.
Gravel areas are particularly challenging. It's impractical to hand-weed a gravel driveway that is covered with thousands tiny weeds with their roots deep in the compacted soil beneath. Here an initial spraying with an herbicide to kill the current crop of weeds may be justified, followed by applications of corn gluten and a fresh layer of gravel to prevent further seeds from sprouting. A weed flamer is useful to knock back any persistent weeds. Be sure to begin corn gluten applications in late winter before any weeds get started.
PREVENTION IS THE KEY
As with human health, prevention is the best treatment for garden health. Protect soil with mulch or ground covers to prevent weeds. Use an organic pre-emergent early in the season to control weed seeds, especially in areas that are difficult to hand weed. Pull weeds whenever you see them, before they bloom and spread their seeds. Water judiciously, using soaker hoses or drip irrigation systems to deliver water directly to your plants while letting weeds and their seeds go thirsty. With these simple preventative measures, you can control weeds in your yard and reduce any need to blast them all away with toxic chemicals.
Learn more about this author, Karen Bledsoe.
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Yes
To start, you should not use pesticides to control garden weeds, because the term "pesticides" includes all applications that control pests: insects, weeds, rodents, etc. Specifically, one should use herbicides to control weeds; I make this distinction at the outset to underscore my point, that use of pesticides in general is safe and effective when they are used properly. The title of this debate automatically fails in this regard, since it would imply that one could apply an insecticide to one's garden in an attempt to tackle some weeds. Obviously, this wouldn't work and it could unnecessarily introduce an insecticide into your garden.
The only time it makes sense to resort to herbicides is when the potential damage caused by the presence of weeds would exceed the expense of making the application. Generally, this only is a consideration of commercial farmers, not the backyard hobbyist. To hobby gardeners, it is a question of aesthetics and time trade offs - is the sight of the weeds unbearable to you, or would the time an energy spent pulling weeds make selective herbicide use a better option?
If the decision is made by you to use herbicides in your garden, you must be careful to select the proper types and use them according to their label instructions. The two main types of herbicides are "pre-emergents", which stop weeds from growing in the first place, and "post-emergents", which kill existing plants. Beyond that you have selective herbicides that target only broad-leaf plants, and general herbicides that kill all plants. You must be careful to select the one you need to control what you want controlled, but that would allow other plants to flourish, such as your rows of prized peas.
Finally, one must pay attention to proper use and disposal of herbicides (or any pesticide for that matter). The vast majority of environmental problems that come from any sort of pesticide use result from misuse of the products. The pesticide products available today are engineered to be safe and cause little to no environmental or human health impact, but only when they are utilized properly.
Learn more about this author, Paul E. Zimmerman.
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