Issue 2, May 7, 2019

Herbicides – Important Tools in Weed Control

Mechanical and cultural methods are important tactics of weed control.  The best weed control programs are ones that take an integrated approach – integrating various control tactics or using various control methods, rather than relying solely on herbicides for example.

I am a home gardener and I use non-chemical methods of weed control whenever possible.  Mulch?  Bring it on thick!  Plastic around the veggies?  You bet!  Dig a trench around the beds so grass can’t invade?  Hope you can jump, Quackgrass!  I always have tools and gloves at the ready.  But I also know that sometimes, persistent weeds happen and weed control efforts can take many, many man hours and sore muscles often result too.  In these cases, stronger, more efficient means of control are necessary.

Weeds can be unpleasant to handle.  Some weeds have thorns or prickles such as multiflora rose or bull thistle.  Others cause an allergic reaction if skin comes into contact with it such as poison ivy and wild parsnip sap.  Catchweed bedstraw can stick to skin like Velcro, causing pain when ripped off.  Mature ragweed can be miserable to work around for allergy sufferers.

Sadly, some weeds simply cannot be controlled completely by hand pulling alone.  Many perennials will produce new growth if you merely cut back the plant at the base of the soil.  If you fail to remove all of the underground portion, you can bet money that the plant will return. 

For annual weeds, repeated tillage can be used to eventually deplete the weed’s stored food reserves.  However, tillage can help to spread perennial weeds that produce rhizomes, such as Canada thistle, bindweed, and mugwort.  Tilling the soil can also bring more seeds to the surface where they can germinate.  It is a disappointing situation when you end up with even more weeds!  In addition, tilling can also result in erosion and lost moisture.

For large areas, weed removal can be extremely time consuming if even possible.  Weeds may be physically impossible to reach or be too numerous to handle.  Arthritis or back pain may interfere with weed removal efforts.  Finding willing workers may be challenging as well.  When protecting yield or even retaining customers, weed control efforts must be timely.  Weeds that are allowed to flower and set seed will continue to be a problem year after year.  When rain prevents timely physical removal, weeds will continue to develop while you watch from your window.

Fortunately, herbicides are available to use in problem situations such as these.  Herbicides are often less labor intensive, less time consuming, and more economical.  However, they are not suitable for every weed-control situation.  Financial and environmental risks should be evaluated including the proximity of sensitive plants, weather conditions, site conditions (topography, soil texture, proximity to ground- or surface water), etc.  Care should be taken to reduce impacts to non-target species. Local pesticide ordinances and application methods and equipment should be considered as well.  Chemicals are registered (labeled) for specific areas and application methods.  They are best used to complement other methods of vegetation control.  When used properly, chemicals can be a valuable asset to a successful vegetation management program.

Herbicides can:

  • cost less than hand weeding.
  • provide timely weed control and prevent germination of weeds in the first place.  This can allow for timelier planting.
  • provide long-term control with residual products lasting up to several months.
  • be used in closely planted crops where tillage would result in injury to the crop.
  • reach weeds growing in obstructed or hard to reach locations.
  • result in more complete kill of perennial weeds including trees, which can resprout profusely.
  • prevent soil erosion and fuel costs associated with repeated tillage.

Of course, advantages come with disadvantages.  Labels must be carefully read and followed to avoid injury to non-target plants.  Appropriate personal protective equipment (PPE) must be worn to prevent exposure.  Good management decisions must be made to prevent herbicide resistance.  Scouting should always be used first to determine if there is a need to use chemicals.

One last bit of gentle guidance to fellow gardeners, please keep in mind that what works for you may not work for everyone.  Every situation is different.  Everyone’s personal values differ.  To suggest that someone simply should use hand weeding is misguided.  It does not take into consideration all of the factors at hand.  Professionals and home gardeners need as many tools as possible in their weed control tool box.  Herbicides remain a valuable tool. 

Michelle Wiesbrook

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