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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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Should we use pesticides to control garden weeds?
This is a misleading title as pesticides are the generic group of chemicals used to control fauna as apposed to flora. Herbicides are used to control weeds and there are three main categories each having a very differing effect on how to manage a weed problem. Residual types remain in the soil and stop the development of the emerging seedling, the one most commonly used being they type for pathways. These are total killers and wipe out all plant life they must never be used on cultivated land. However, in the commercial industry residual weed killers have been developed that are selective; they only poison plants of a differing family. For example if growing Brassica they will kill all the Umbelliferae plant groups leaving the Cruciferae well alone. This is an ideal commercial solution as it allows intensive crop rotation which is excellent for disease problems but removes what is termed volunteer plants, or those left over from a previous crop.
The second group is the contact type and as the name implies they work by poisoning the leaves of the plant. These are not so good and perhaps give herbicides as bad image. Seldom do they cure the problem as many weeds are perennial and return from the roots. Attempts have been made at making these selective indeed the earliest form was sulphuric acid which was used to remove Dicotleydons from Monocotyledons, or better put broad leaved weeds from the grass family. The idea being that the spray would land on the flat leaf and kill it but run off the smooth stems of the grasses. Many of the annuals have become immune to them and there is evidence that in some instances such as groundsel applications of the chemical encourage the weed to grow faster in order to set seed. If possible I would always hoe of either by hand or mechanically on large areas all annual growth.
The last group is the most useful and this is the translocated type, by which the chemical is pumped round the plant using its own vascular tissue. This will kill both the roots and the stems and is perhaps the only effective means of controlling invasive species such as ground elder. A sub group from this use a plant growth hormone to control brash weeds. Basically it forces them to grow unnaturally fast noticed by the twists and turns in the plants growth soon after application. This uses up the plants food reserves and eventually kills the weed.
So are they useful? The main problem is people don't understand the type of weed they are killing thus use a one size fits all approach this seldom ever works and thus they become disappointed with the results often blaming the herbicide .The second problem is one of timing and application. Certain weeds need to be actively growing for the chemical to be pumped around; all too often they are sprayed when in seed making the operation pointless. Thirdly there is an often misunderstood idea that herbicides poison the soil, I have shown that one type does. However, some actually break down into beneficial compounds improving fertility for subsequent plants.
Today we are all rightly concerned with environmental issues and taken at last a keen interest in how and where our food is produced. All too often I have seen the best of intentions in a vegetable garden ruined within the first year as the owner has been unable to control the weed growth become disillusioned and given up. Interestingly I now have very few major weed problems what I do have can easily be controlled with out too many sprays. Indeed I could obtain organic status. However, this is a result of chemically controlling the land until I could catch up
Learn more about this author, Simon Woollen.
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