Alternate Methods of Non-Selective Weed Control

By Edward Dywan, B.Sc.

Due to environmental concerns and public perception issues, it is becoming important for weed control professionals to consider methods of weed control other than pesticide application by spraying.  This article describes some alternate weed control technologies that offer distinct advantages over conventional means of weed control.

     There are two new non-chemical means of weed control.  They both rely on the application of heat to the target species in order to achieve control.  One uses infrared heat and the other uses superheated water.  The heat produced by these devices burst protein and moisture cells within the plant.  The weeds are not charred but wilt and become dark green in colour.  Their protein cells are destroyed; they cannot photosynthesize and therefore die.

     There are several advantages of using heat as opposed to chemical means to control weeds.  The risks of chemical spills, spray drift, chemical run-off, wastes, and rinses are eliminated.  Weeds are not able to develop resistance as they can with chemicals.  Beneficial microorganisms in the soil are not damaged due to minimal ground penetration.  Heat can be used in all weather since there is nothing to wash off or blow away.  The applicator is more comfortable because masks and goggles are not required.  Special licenses are not required.  Finally, the public perceives less risk in non-chemical applications especially in high profile areas such as parks, playgrounds, and sports fields.

     The new Infra-Weeder weed control equipment uses infrared heat to kill undesired vegetation.  Infra-Weeder equipment is a Swiss development.  It has been used successfully in Europe for over eight years and in British Columbia by Forevergreen Landscaping and Maintenance for over three years.  Infra-Weeder equipment uses a propane-fuelled ceramic heating element that develops temperatures up to 1800 degrees Fahrenheit (1000 degrees Celsius), which applies infrared radiation to weeds.  Because of the high heat produced by this machine, it eliminates windborne weed seeds, bacteria, and moulds on the ground surface.  In addition, the shielded heat element prevents heat from radiating upwards or sideways so vegetation can be controlled alongside desired species without harm.  The most popular unit, the hand held Eliminator, runs four hours on a standard disposable propane torch cylinder.

     Due to the nature of infrared heat application, a close proximity must be maintained between the heat element and the target species, therefore it is restricted to use on relatively smooth surfaces.  The use of Infra-Weeder equipment is slower than liquid herbicide application, and sometimes a second application is required in the case of mature weeds.  This makes it an excellent addition to an existing chemical weed control program especially for sensitive areas such as near pools, patios, and areas where children play.

      Hot water is employed by the recently developed Aquacide vegetation control system.  This new technology uses a process in which water is super heated on demand under low pressure and then pumped through a heat resistant hose to an application delivery system.  This super-heated water when applied to the ground surface will eradicate unwelcome vegetation.  The extreme heat of the water immediately breaks down the molecular structure in the plant killing it on contact.  The Aquacide can be used in many applications including the line marking of playing fields, around public areas, between asphalt and curbs, as well as growth around fencing and poles.  For additional information regarding the Aquacide, contact G.C. Duke Equipment Ltd. in Burlington, Ontario 1-800-883-0761.

     The application of salt to vegetation has long been known as an effective herbicide.  Salt dehydrates the root of taproot weeds through reverse osmosis.  While not a new method of weed control, there has been a problem in applying salt accurately and in small enough quantities to avoid the destruction of neighbouring desired plant species.  The E-Zee Weeder Dandelion Killer is a device developed and manufactured in Sweden.  It provides pinpoint application of coarse pickling salt to the target weed with a simple plunger mechanism.  Tests performed by Rittenhouse in 1999 have shown that salt is effective on all taproot weeds including dandelions and thistles.  After a week, the root is dead.  After two weeks, new grass covers the withered dandelion.  The small measured quantity of salt is dissolved and washed away by rain over time so as not to significantly affect the salinity of the soil in the area.  Although this is an excellent means of weed control in lawns, it is important to use caution in flowerbeds, as some species of plant may be more sensitive to the localized temporary increase in salinity.  Due to its simple method of operation and light one-pound weight, a weed control operator can easily treat up to 500 dandelions per hour.

     New advents in chemical weed control include applicators that use straight Roundup ®.  These include the German Manta Ultra Low Volume (ULV) applicator as well as the Spanish Pulmipure Roundup ® applicator.  The advantage of using straight Roundup ® is the elimination of mixing chemicals.  Both systems use a battery powered high-speed rotating disk that creates a very fine well-defined spray.  The small 120-micron droplets give better foliar coverage, but are very drift resistant.  The applicators’ small, 250 ml, chemical tanks make them much lighter and easier to handle than backpack sprayers while lasting forty five minutes to an hour between fills.

     Wick type Herbicide Applicators are not new but are worth mentioning because they present an economical yet viable alternative to spraying of chemicals.  They use a rope or fleece as a wicking medium that is saturated with herbicide.  The herbicide is transferred to the target weed by simply wiping against it.  Since weeds usually grow faster than desired species, it becomes possible to contact only weeds by maintaining a wick height just above that of the desired species.  Because there is no spray, there is no associated drift.  There are several different manufacturers of wick type applicators and they range from small hand held units to large boom mounted wick banks for agricultural applications.

     An interesting development in herbicide application for land clearing operations is the new Sprout-less herbicide applicator.  Rather than clear an area with a brush saw and then go over the area again with a backpack sprayer, the Sprout-less herbicide applicator is an attachment developed and manufactured in Canada, that installs under the blade of most commonly used brush saws in less than 5 minutes using the existing bolt and nut.  When filled with an herbicide such as Vision ® it applies the herbicide to stumps and cut stems as they are being cut.  This can save a considerable amount of labour.  Field trials have shown up to an 85% efficacy.  Because there is no spraying involved, spray drift is eliminated and operator exposure to chemical is dramatically reduced.