With the weeds gaining ground, data and innovation are back in focus: new REM maps paint a picture of more than 25,8 million hectares already coexist with resistant or tolerant biotypes, while a recent trial validates the use of electricity for weed control in vineyards without damaging the crop or the soil.
The problem also reconfigures agronomic practices: Direct Seeding gives up space and Tillage makes a comeback driven by weed control, although technical evidence indicates that this shortcut does not solve the problem and can compromise soil health if it becomes widespread.
The expansion of resistant weeds: data from the new mapping
The Aapresid Pest Management Network presented the seventh edition of its Weed Maps, a survey that confirms the sustained expansion of the problem: the presence of 34 species (28 resistant and 6 tolerant) and, for the first time, they joined Bassia scoparia RALS, Bassia scoparia RALS+RG and Sonchus oleraceus; In 13 species Abundance was also measured to determine the area actually affected.
The distribution shows a clear pattern: Conyza spp., Amaranthus spp., Eleusine indica, Echinochloa colona y Sorghum halepense, known for his rhizomes, resistant to glyphosate are present in much of the agricultural area, while others such as Turnips, Bassia scoparia o Kali Salsola are concentrated in the south, and Cynodon hirsutus RG is almost exclusive to the province of Cordoba.
As for the dynamics, Conyza resistant to ALS group herbicides once again led geographic growth for the second consecutive cycle, followed by Digitaria sanguinalis RG, Nabos RALS and Nabos RG, consolidating their potential for advancement.
By affected area, Conyza RG and Amaranthus RG each exceeds 25 million hectares. Behind them appear Sorghum halepense RG, Echinochloa colona RG, Eleusine indica RG and the Chlorideas group, with areas close to 12–14 million hectares. They are added commelina erecta y Borreria sp tolerant to glyphosate (11 and 4,9 million hectares) and, among those resistant to graminicides, Sorghum halepense (4,1 million) and lolium sp (1,8 million).
In addition to the increase in surface area, the REM warns of a greater complexity with overlaps of resistant and tolerant species in the same plots. Mapping allows for monitoring developments by province and species, anticipating threats, and prioritizing management strategies at the regional and plot levels.
Impact on agricultural practices: pressure on no-till farming
The spread of weeds also impacts soil management: according to the latest REM survey, 82% of the agricultural area remained in Direct Seeding in 2024/25, but the 18% was worked with tillageThe decline is most pronounced in Entre RÃos, Chaco, and Santa Fe (exceeding 20%), while in Buenos Aires, Córdoba, and Santiago del Estero the percentages are lower but significant due to their large surface areas.
The main trigger for circumstantial plowing is weed control: 53% of the cultivated area intervention was made for resistant or tolerant weeds, and in some provinces that proportion It is close to 70%The battle against weeds has thus become the number one cause of the breakdown of Direct Seeding.
Scientific evidence does not support this outcome: work on plots with more than two decades of Direct Seeding in Carlos Casares determined that the Occasional tillage does not significantly reduce the quantity or diversity of weeds; what it does is vertically redistribute the seed bank, leaving viable material buried that can germinate in future campaigns.
The agronomic cost is not minor either: resorting to the plow implies loss of cover, degradation of soil structure and reduced infiltration, impacts that can take years to reverse. Recommendations include maintaining the comprehensive vision of No-Till with crop diversification, service crops, and sequence intensification.
Electrical control in vineyards: results, limits and safety
A pioneering study in four vineyards near Yallingup (Western Australia), carried out during 2022 and 2023, evaluated a tractor-mounted unit with a 36 kW and side applicators with electrodes in contact with weeds to transmit shocks that reach the root.
The results were conclusive: the electrical control achieved biomass reductions from 84% to 87% with 24 and 36 kW configurations, values ​​statistically comparable to 88% glyphosate + amitrole and higher than 65% of mechanical clearing.
Safety for cultivation was supported by measurements of NDVI without differences in the development of the vines (Vitis vinifera) and the absence of observable damage. When working without chemical waste and with deep action, the technique offers a clean profile in the field and in food.
It was also quantified risk of fire under controlled conditions with dry biomass: an average of 0,37 smoke or flame incidents per m² when the operation was carried out on completely dry waste, with greater risk at speeds of 1 km/h due to the longer electrode-plant contact time.
Instead, during spring applications (September in the southern hemisphere) with moist soil and vegetation, no fires were recordedThe operational recommendation is clear: safe use in winter and spring, and avoid its implementation in summer or autumn with dry biomass.
Limitations persist: the working speed (1,1–1,4 km/h) is low compared to herbicides (4 km/h) or brush cutters (3 km/h), and fuel consumption is high. Its effectiveness at higher speeds and with different species, ages and densities of weeds; in addition, very wet soils could disperse the current and reduce its effectiveness.
Even with these cautions, the technology fits into integrated management programs and its combination with is already being tested autonomous tractors to alleviate speed limitations on larger farms.
Keys to integrated weed management
The technical consensus goes through combine tools: well-designed rotations, service crops, alternating modes of action in herbicides, selective mechanical control and, where it adds value, electrical control and integrating the plant allelopathy.
Tracking is essential from the plot to the landscape: crossing the batch monitoring with the REM mapping allows you to prioritize target species, detect overlaps and choose the most effective intervention windows.
Reducing dependencies helps prevent resistance: adjusting doses and timing, lower the pressure on glyphosate in fallow land and avoid reactive decisions that resolve a campaign but aggravate the problem in the medium term.
Operational safety and sustainability must go hand in hand: calibrate equipment, respect humidity conditions for electrical control and minimize impacts on biodiversity and waterways are key practices to maintain productivity and social acceptance.
The picture drawn by the data and the tests is clear: the resistant weeds advance, force us to rethink tactics and open up space for solutions such as electricity, always inserted in a diverse, planned management without re-tillage what cost so much to preserve.
