The existence of maps that show the presence of resistant biotypes and main tolerant weeds in Argentina is valued by different actors in the production: producers and advisors to know if in their area there is a certain resistant or tolerant weed and thus increase caution, especially the monitoring; input companies to direct the search for solutions and their sales force towards the most affected areas; the State to dimension the problem and take containment measures, generation of solutions, etc.

Mapped weeds

In 2013, REM mapped for the first time the presence of resistant and main tolerant weeds in Argentina. Given the dynamics of weeds, in 2015 that information was updated and progress was made including the new resistances determined after 2013 and at the same time some species were better differentiated than in the first version they were included together (such is the case of resistant Amaranthus hibridus and palmeri that were grouped as Amaranthus sp. and of the tolerant Gomphrena pulchella and perennis that were grouped as Gomphrena sp.). In 2017, this information was updated again, incorporating two new resistant biotypes confirmed after 2015. In the last year Conyza sp has not been mapped, given its presence in almost 100% of the surface, which made its location unimportant; and neither did Commelina erecta mapped. But as a main difference, in 2017 the abundance of 6 very relevant weeds has been mapped, in addition to its presence. Abundance was defined as the "percentage of lots that were applied or should have been applied to control the weed in question." In 2019, Eleusine indica are added are multiple resistance to glyphosate and ACCasa and Conyza sp. with resistance to ALS. On the other hand Brassica rapa and Hirschfeldia incana with resistance to Glyphosate, ALS and 2,4D were grouped under the name of Turnips with their respective resistance. Regarding abundance, the same 6 weeds were relieved as in 2017 and added to turnips with glyphosate resistance.

Weeds mapped by REM each year for its Presence (P) and Abundance (A)

1 It is the sum of Amaranthus quitensis and Amaranthus palmeri in order to compare their progress between years since they were not mapped separately in 2013
2 Fop Graminicides
3 They change their denomination and are grouped in “Turnips” with their respective resistances.
4 Includes biotypes of Conyza bonariensis and Conyza sumatrensis. This weed was considered glyphosate tolerant in 2013 and resistant in 2015 because scientific studies confirmed it
5 Fop and Dim Graminicides
6 Fop Graminicides
7 Includes biotypes of Lolium multiflorum and Lolium perennial
8 Graminicides Fop, Dim and Den
9 It is the sum of Gomphrena pulchella and Gomphrena perennis in order to compare their progress between years since they were not mapped separately in 2013

The maps include information on 200 parties and departments in 10 Argentine provinces, which represents almost the entire agricultural area of the country. To obtain this information, 200 professionals were consulted and reviewed by 15 referents distributed throughout this geography.

Colors of the maps

In presence maps, it is marked with three colors: red, yellow and orange. The first of them for cases where technicians were sure of their resistance by observing it in repeated applications. Yellow was used in cases that are suspected, but cannot be assured. However, this data is of great interest because it is causing inconvenience in the control and great attention must be paid. Orange was used to mark the presence of tolerant weeds.

In the abundance maps, a gradient of colors was used, being the most intense where the weeds are most abundant.

Limitations

It is possible that in some party there is presence of resistant and tolerant biotypes and they do not appear on the map, due to ignorance of the people consulted. And on the other hand, it is only possible to estimate the area affected for the weeds that their abundance was mapped.

Thanks

To advisors who selflessly responded by providing information about their area.

To weeds specialists of public institutions that made contributions to the presented information.