Following the adoption of GM crops, overall pesticide use in Brazil increased 1.6-fold between the years 2000 and 2012
Here's an extremely useful study with a clear abstract. The study found that GM crop adoption in Brazil has driven up pesticide use 1.6-fold between the years 2000 and 2012.
The cumulative growth in pesticide use was three times higher than the growth in productivity (kg/ha) and 10 times higher than population growth for the same period. Each year, pesticide use per capita increased by 7%, while productivity increased by only 3.5%.
Use of genetically modified crops and pesticides in Brazil: growing hazards
Almeida, V. E. S. D., Friedrich, K., Tygel, A. F., Melgarejo, L., & Carneiro, F. F. (2017). Ciência & Saúde Coletiva, 22(10), 3333-3339.
Genetically modified (GM) crops were officially authorized in Brazil in 2003. In this documentary study, we aimed to identify possible changes in the patterns of pesticide use after the adoption of this technology over a span of 13 years (2000 to 2012). The following variables were analyzed: Pesticide use (kg), Pesticide use per capita (kg/inhab), Pesticide and herbicide use per area (kg/ha) and productivity (kg/ha). Contrary to the initial expectations of decreasing pesticide use following the adoption of GM crops, overall pesticide use in Brazil increased 1.6-fold between the years 2000 and 2012. During the same period, pesticide use for soybean increased 3-fold. This study shows that the adoption of GM crops in Brazil has led to an increase in pesticide use with possible increases in environmental and human exposure and associated negative impacts.