Herbicides are chemicals used to stop the growth of weeds, in order to prevent weeds from competing negatively with crops or other plant species of interest, or they are also used to completely prevent the growth of plants in a determined area, for example, sidewalks or roads. Herbicides are the main tool used in modern agriculture to control weeds.
When a single herbicide or class of herbicides are used repeatedly without the simultaneous use of other weed control methods, the emergence of weed populations that are resistant to these herbicides is possible.
This repeated use of herbicides with the same mode of action (how a herbicide affects weeds) subjects weed populations to a selection pressure that can lead to an increase in the number of resistant individuals that survive in the population. The population of resistant weeds may increase to the point where commercially acceptable control of weeds can not be achieved by the application of that herbicide alone.
Thus, the use of herbicides with a different mode of action and / or the use of other methods of weed control may be necessary.
Glyphosate is one of the most used herbicides in today’s agriculture and several weeds have developed resistance to glyphosate. Weeds resistant to glyphosate have been found in areas where glyphosate has been used to control weeds in orchards, roadsides …
As glyphosate-resistant weed biotypes have been identified, they have been effectively managed with other herbicides and / or cultural practices, according to the case, following the appropriate recommendations.
For a weed to be confirmed as resistant to a herbicide and listed in the International Survey of Herbicide Resistant Weeds, it must meet the following criteria:
– To comply with the necessary requirements for the definition of weed resistant to a herbicide established by the Society of Disherbology of America (Weed Science Society of America).
– Confirmation of data using acceptable scientific protocols. – The resistance must be hereditary (passed to the next generation).
– Demonstration of practical impact in the field.
– Identification as a problem weed, not the result of deliberate or artificial selection. Worldwide, weed species confirmed as resistant to glyphosate have been found in conventional and unconventional crops. Species found outside the US They are: Lolium rigidum, Lolium multiflorum, Conyza spp., Conyza canadensis, Eleusine indica, Plantago lanceolata, Sorghum halepense, Euphorbia heterophylla, Parthenium hysterophorus, Urochloa panicoides and Echinochloa colona.
Management recommendations and herbicide management – Start with clean fields and early weed control.
– Add other herbicides and cultural practices where appropriate.
– Use the correct proportion of herbicide at the right time.
– Control weeds throughout the campaign and reduce the bank of weed seeds.