Jan. 16, 2017
The first confirmed case of resistance to 2,4-D herbicide was detected in the central part of the province of Buenos Aires in Argentina. Identified as Brassica rapa (L.), commonly known as "Nabo," it is a weed found in nature in all the provinces of our country.
In general, it is present in paddocks and stubble, along the banks and in marginal areas. The species is native to Europe and Asia and is under focus worldwide for bringing down productivity in crops and grazing fields.
It belongs to the Brassicaceae family, comprising approximately 350 genera and 3,000 species, noted for their cosmopolitan distribution.
In the central and southeastern part of the province of Buenos Aires, during the last two years, controls and treatments with 2,4-D have been studied. There have been suspicions of the presence of a resistant biotype in Azul, Province of Buenos Aires, Argentina.
Turnip escapes on a field of barley, applied with 2,4-D ester ethylene EC 100% 280g ea/ha in a mixture with picloran SL 24% 24g ai/ha.
In order to confirm resistance, the Plant Therapeutics Research Group of the National University of the Center of the Province of Buenos Aires, started exploratory tests to evaluate and determine the resistance index of the biotype. Under greenhouse conditions, dose response bioassays were performed.
For this, we collected weed seeds from those lots where control failures were recorded and these were planted in pots. The plants grew up to a pink state 6 leaves and were applied with 2,4-D dimethyl amine CS salt 60% in doses of 0, 50, 100, 200, 400, 800, 1600, 3200 and 6400g ea/ha. It was observed that the biotype plants were resistant to a dose of up to 800 g/ha while those of biotype were susceptible up to 200g ea/ha.
The resistance index calculated from the final dry weight 42 days from the application was found to be approximately 5.
It is to be noted that in our country, there are confirmed records of multiple resistance of this species to glyphosate
and ALS inhibitors, and specifically in Azul, resistant biotypes to EPSPs and ALS were confirmed by this working group. It is noted that these biotypes could be compared with the reported 2,4-D resistant biotype.