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The pros and cons of glyphosate

The use of drones to spray glyphosate for controlling illegal crops needs to be very careful as the increased concentration and other coadjutants intensify their action and impact neighboring areas. Although when applying at heights, less herbicide would be drifting in the wind; but also there would be the risk of polluting water sources and impacting wildlife.

Glyphosate is a synthetic pesticide and herbicide in use since the 70s and as all pesticides; it is toxic to a certain degree. The herbicide has shown to be effective for controlling weeds and illegal crops; but using it frequently may cause resistance, accumulation, and toxicity in soil and water. Glyphosate is an excellent tool for farmers and crop dusters; but as it does not break down rapidly and may leave residue, cause resistance and pollution.

Its use in Colombia, the increase of use for controlling illegal drugs crops, use of coadjutants and the great diversity of environments where it is applied, create the need to become cognizant of the implications it can have over the environment.

Characteristics

Glyphosate (N-(phosphonomethyl)glycine) is formulated mainly as an isopropylamine salt, classified as non-symmetric and having systemic action, in other words, they are absorbed by plants. This compound has an ample action spectrum which helps to control annual or perennial problem plants, as well as dicotyledonous and monocotyledonous plants. It is also one of the most used pesticides worldwide, including Colombia where its use has increased in the last years due to the glyphosate-tolerant crops (transgenic crops).

Glyphosate is a non-selective systemic post-emerging chemical, for foliar application which translocates in the plant, mainly though sap vessels and conduits (phloem).

The herbicide is sold in Colombia under several brand names, such as:

  • Roundup (Monsanto)
  • Batalla (Bayer)
  • Stelar (Dow Agrosciences de Colombia)
  • Glifosol (Coljap)
  • Socar (Aventis)
  • Glifosan (Agrogen)
  • Regio (Quimor)
  • Coloso (Basf)
  • Panzer (Invequímica)

These products mainly contain three different basic ingredients: Glyphosate isopropylamine salt (the active ingredient), a surfactant and water. Differences in the commercial formulation are principally in the concentration of the active ingredient and the class or mixture of surfactants. In some cases, commercial formulations may have additional surfactants.

Commonly, herbicides have surfactants and other components which facilitate storage and water mixing in spraying tanks. The formulation also helps retention over application and penetration areas. To control illegal drugs and in determined climate conditions, the herbicide action is increased by use of surfactants or oily coadjutants, which mixed together in the tank with the herbicide can boost its performance.

An inadequate coadjutant may cause a loss of venomous activity or crop damage to the crop and environment; therefore it should be used only with the suggested coadjutants printed on the label of the bottle, the mixture, and crop situation.

Environmental impact

Glyphosate has been considered for many years as a compound with “good toxicological profile” for not leaving residue in the soil and relative fast breakdown in the soil. Besides due to its strong soil adsorption its runoff is very limited. However, as of late, several studies have indicated that glyphosate seems not be as innocuous as believed, hence the controversy over its environmental impact. Numerous documents sustain that glyphosate persists in the environment and its metabolite known as aminomethylphosphonic acid (AMPA) has been discovered in superficial waters and glyphosate in underground waters.

Breakdown of the herbicide occurs mainly by the action of microorganisms, both on the soil as in water and also aerobically and anaerobically. Therefore this depends on the type of soil, clay, texture, organic matter content and the types of microorganisms present in the soil.

Studies carried out at the Universidad Nacional de Colombia (UNal) Faculty of Agrarian Sciences discovered that the use glyphosate for controlling weeds in commercial crops in the Province of Tolima allowed contact of the herbicide with the foliage which later falls onto the ground of no more than two millimeters of glyphosate, which remains on the surface.

They also discovered that sandy soils have large particles with small surface area for adsorption; clays have large surface areas and high capability to absorb glyphosate; organic matter is the most important factor to determine glyphosate adsorption; low glyphosate mineralization rates allow to infer that the herbicide may become an environmental pollution issue, due to its persistence in the soil.

 

Consejo Editorial