An agronomy researcher demonstrated strategies for avoiding herbicide-resistant weeds
Herbicides are chemical substances used to suppress unwanted plants (weeds). Their action is based on blocking important biochemical processes. For example, diuron interferes photosynthesis, and glyphosate, the most popular chemical of the group, influences the synthesis of certain amino acids. Herbicides play an important role in agriculture, as chemical weeding can be used instead of less efficient seasonal labor. The first application of a chemical destroys the majority of harmful cultures, but plants with genetic defects (such as changes in the chemical process targeted by a herbicide) may remain. These weeds become resistant to the influence of the chemical, survive, and reproduce passing their broken but useful genes to future generations. If a farmer uses the same herbicide next time, the survived weeds would produce numerous resistant offsprings able to interfere with the crops (by consuming water and nutrients from the soil, shading, or discharge of phytotoxins).
"Herbicide resistance development is globally a serious agrarian question in many agro-ecosystems. The situation is the worst in the USA: right now, there are 156 resistant weed species registered there. So that, farmers have to spend additional $50 per hectare each season," says Zargar Meisam (Ph.D.), Associate Professor of the Agrobiotechnological Department of RUDN University. Mentioned findings were presented in International Conference on Healthcare and Life-Science Research, Malaysia.
Authors of this research found out several main issues, as the number of resistant weed species is growing up globally. Almost 360 herbicide resistance in 180 plant species for several seasons have already been identified and registered in different scientific papers. Moreover, the number of resistant individuals will swiftly increase with repeated use of the same herbicide or those with similar mode of action (MOA). Resistance management methods are naturally adopted reactively when a resistant weed species has become problematic and should be suppressed.
For example, a widely spread weed called Swiss rye grass (Lolium rigidum) is resistant to at least 12 chemicals. Herbicide resistance in weeds is observed all over the world. The most abundant data is available for North and South America, Australia, Europe, and a major part of Asia. Zargar Meisam scientifically determined some significant resistance management approaches due to obtain sustainable agricultural systems:
"Overall, it is essential to change a chemical every season, if herbicides with different target processes are alternated, the weeds won't stand a chance. The plants resistant to one chemical would leave seeds, but they would die next year under the influence of a new chemical. Therefore, the resistance gene won't get fixed. Unfortunately, using multiple herbicides with different MOAs is one of the least-adopted methods for herbicide resistance management, despite this practice being frequently identified by scientists as an efficient way to reduce the risk of resistance development. More commonly, growers prefer to use one herbicide that still provides good control on susceptible weeds while adding a second herbicide to control resistant weeds. Although the most favorable practice is to proactively use annual herbicide rotations and sequential applications before resistance evolves, that requires growers using multiple herbicides with different MoAs".
Provided by RUDN University
