Vegetation Control

Herbicides – Use and Application

Selective use of herbicides

The work sometimes consists in cutting the longest stems of certain tree species which are incompatible with power system operations and spraying their leaves and stems with products such as Garlon 4 (triclopyr). The mixtures are used in highly diluted form, i.e., one part herbicide to one hundred parts water. Trees and shrubs are treated during the summer, when they are growing.

Another method involving herbicides: selective mechanical cutting is done, then a herbicide mixed with mineral or vegetable oil is applied to the stumps to prevent the formation of stool shoots. In certain cases, herbicide capsules may be manually injected at the base of the stem using a spot gun.

All the companies hired by Hydro-Québec to do this type of work have the appropriate permits, and forestry workers who use herbicides must have the required certificate of competence, which is issued by the Ministère du Développement durable, de l'Environnement et des Parcs (MDDEP).

MDDEP statistics show that the quantity of pesticides used by Hydro-Québec for vegetation control accounts for only 0.4% of the total amount sold in Québec every year.

Proper application of herbicides

• The use of herbicides is always preceded by an environmental study of the area.
• As stipulated in the Pest Control Products Act, Hydro-Québec uses only chemicals certified by the Pest Management Regulatory Agency, a branch of Health Canada.
• None of the herbicides used by Hydro-Québec is recognized as being a carcinogen. All are biodegradable and are not prone to bioconcentration. Relatively non-toxic, they do not present a hazard to bees.
• Herbicides are applied selectively: only large-growing trees that could reach as high as power lines are treated. For this reason, we protect many shrubs and bushes (dogwood, red currant, wild raspberry, viburnum, yew, hazel, grasses, etc.) during herbicide application.
• Hydro-Québec makes every effort to spray large-growing trees when they are still small, since this requires less herbicide.
• Herbicides are mainly used in wooded and agroforest areas. Special protection measures are used for all areas containing sensitive components.
• Selective herbicide application is more efficient than mechanical cutting for controlling the growth of woody vegetation (trees). Contrary to cutting, which increases the thickness of undesirable stems, herbicides prevent the reproduction of trees through clump shoots and root suckering.
• Over the long term, the proper use of herbicides leads to a preponderance of grass and shrubs under and around power lines, thus requiring less intervention.
• In general, Hydro-Québec uses only mechanical cutting to control vegetation in rights-of-way in 70% of all cases. The other work consists of a combination of mechanical cutting and selective application of herbicides.

Hydro-Québec complies with provincial legislation concerning the use of pesticides (Pesticides Act and the Pesticides Management Code) and follows the best practices set out in the booklet titled Phytocides en milieu industriel : bon sens, bonnes pratiques (Les Publications du Québec).