**Acknowledgements**

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

restricted in relation to the alternative herbicide options available [25].

Brazil exceeds R\$ 9 billion annually in soybean cultivation alone [25].

Brazil is a consolidated agricultural power; however, the large size of its agricultural activity, especially the intensive production, makes it highly dependent on pesticides for the management of phytosanitary issues, which has led to the emer-

Much of the Brazilian agricultural activity (68.4%) is focused on the production of grains (52.5% soybean, 10.6% maize, and 5.3% other grains) by cultivating herbicide-resistant crop varieties. The introduction, rapid adoption, and high dependence on these technologies and their associated herbicides (58% of the national pesticide market) caused major changes in weed management practices,

Today, herbicide resistance is a fait accompli in Brazil; however, the problem is not rooted in the cultivation of herbicide resistant crops but in the inappropriate use of these technologies as a whole, mainly related to off-season applications and herbicide overdose. Clearly, weed management practices must be constantly changed to prevent or delay the emergence of resistant plants in an area. However, the high specialization of farmers to grow, manage and market one or few crops with similar agricultural tasks limits the implementation of alternatives weed management measures as well as reduce more complex crop rotations (i.e., grains by vegetables instead of grains by grains), since transferring their production system to other crops requires investments in professional training, infrastructure, new agricultural implements as well as in the creation of new marketing networks; otherwise, farmers have no guaranteed economic return. In addition, farmers prefer to continue living with the herbicide resistance, and they are reluctant to adopt integrated weed management measures or new herbicide resistant crop technologies for herbicide

**6. Future trends, challenges, and conclusions**

contributing to the selection of herbicide resistance weeds.

resistance control if their profit margins are not severely compromised.

The management of the herbicide resistance may represent an increase ranging

with no resistance. However, the dimensions of this phytosanitary issue is incalculable, as five glyphosate resistant weeds (*C. bonariensis, C. canadensis, C. sumatrensis, D. insularis*, and *L. multiflorum*), occurring only in soybean, infested ≥25% of the total planted area (20.1 out of 77.8 million ha) of Brazil, and caused R\$ 9 billion of losses in 2017. To know the true economic impact of herbicide resistance, the areas of other crops infested by these glyphosate resistant weeds, as well as areas affected by the other 46 cases of herbicide resistance (species x herbicide x crop situation)

of the costs devoted for weed control in relation to fields

gence of pests resistant to these products.

to latifolicides, scenarios in which the cost of management is more expensive and

According to GherbE monitoring, 59% of soybean area (20.1 out of 34.0 million ha) had infestations of glyphosate-resistant populations of *Conyza* sp., *D. insularis* and/ or *L. multiflorum* in 2017. *Lolium multiflorum* affected 4.2 million ha in the southern states, and this weed occurred simultaneously with *Conyza* sp. in 3.4 million ha*.* The areas infested by *Conyza* sp. and *D. insularis* were estimated at 7.7 and 8.2 million ha, respectively, of which 2.7 million ha correspond to mixed infestations of these two species [100]. On the GherbE website it can visualize distribution maps of these weeds in the different agricultural regions of Brazil [99]. Analyzing the infested area and the control cost according to the infesting weed species, the average cost of resistance management was R\$ 4,918,820,000.00 in 2017 [25]. If a conservative 5% yield loss by weed competition is added, the total cost of herbicide resistance in

**168**

from 100 to 350% ha<sup>−</sup><sup>1</sup>

reported in Brazil should also be considered.

RAC, GMO, and MFGFS thank the "Fundação de Amparo à Pesquisa do Estado de São Paulo—FAPESP" for the financial support (main-grant: 2014/50918-7, subgrants: 2018/15910-6 and 2019/15527-0).
