The corn leafhopper (Dalbulus maidis), which is considered the crop’s main pest, has caused billions in losses to Brazilian production. A new study has quantified the economic impact of corn stunt diseases on Brazilian production. Between 2020 and 2024, Brazil lost an average of 22.7% of its corn yield due to such diseases, whose pathogens are transmitted by the insect vector, resulting in annual losses of approximately US$6.5 billion.

Over the four crop years in the survey, cumulative financial losses reached US$25.8 billion, as approximately 2 billion 60-kilogram bags were not produced.

The findings resulted from the analysis of data by the National Supply Company (Conab) covering historical series on yield, grain production, and corn-planted area since 1976, and economic losses associated with crop damage in Brazil’s main corn-producing regions were estimated.

The findings were published in the international journal Crop Protection and detail how corn stunt diseases and the corn leafhopper have evolved from a minor problem into the biggest challenge Brazil’s corn production has been facing in recent decades. The study was conducted by Embrapa Cerrados (DF), the Agricultural Research and Rural Extension Company of Santa Catarina (Epagri), and the Brazilian Confederation of Agriculture and Livestock (CNA).

An overview of the losses

In addition to statistical data, the researchers used information collected by the Campo Futuro project, an initiative by CNA and the National Rural Learning Service (Senar). The surveys were conducted in 34 municipalities that represent Brazil’s main producing regions, with the participation of farmers and experts. Based on technical consensus, they identified and estimated the losses associated with the corn leafhopper and the complex of stunting symptoms in each municipality and crop season.

In the first crop year (2020/2021) under analysis, the impact was bigger – 28,9% production loss. In the 2023/2024 crop, the index fell by 16.7%. Meanwhile, spending on insecticides to control leafhoppers rose by 19% over those four crop seasons, exceeding nine dollars per hectare, which significantly increased production costs for farmers.

“The results indicate that corn stunt diseases led to an average loss of 31.8 million tons per year,” Charles Oliveira, a researcher at Embrapa Cerrados and author of the study, points out. In about 80% of the locations surveyed, leafhoppers or leaf damage were identified as the main factor behind the decline in yield.

Larissa Mouro, coordinator of Campo Futuro, emphasizes the importance of the study for the production sector: “The data have made it possible to generate a consistent economic estimate covering the entire country.”

The threat of stunt diseases

Brazil is the world's third largest producer of the grain and one of the leading exporters. According to data from Conab, the 2025/2026 crop is estimated to yield 138.4 million tons, with a production value of approximately US$30 billion.

Currently, two types of corn stunting —pale mottling (Spiroplasma kunkelii) and red mottling (“Candidatus” Phytoplasma asteris)— pose the biggest phytosanitary threat to Brazilian grain production. Both diseases are caused by the corn leafhopper, which also transmits the corn streak mosaic virus and the maize streak virus.

According to the Embrapa researcher, the problem is exacerbated by the lack of preventive treatments for those diseases, which can result in total crop loss, particularly in fields planted with hybrids that are susceptible to them.

Although the pathogens have been known since the 1970s, outbreaks have become frequent since 2015. “Changes in the production system over the past few decades, such as the expansion of double cropping and the cultivation of corn throughout most of the year, have created favorable conditions for the survival of leafhoppers and microorganisms,” Oliveira explains.

According to Tiago Pereira, a technical advisor at CNA, the leafhopper is no longer a localized problem: “We’re talking about losses that directly impact farmers’ incomes, production stability, and the country’s competitiveness. What sets this study apart is that it translates this recurring perception into scientifically grounded data.”

Trends in Brazilian production

Historical data on corn production in Brazil show that the planted area varied little between 1976/1977 and 2011/2012, ranging between 10 and 14 million hectares. It started to grow from the 2015/2016 crop year, reaching a peak of 22.3 million hectares in 2022/2023.

Annual total production and average productivity followed this trend: yields were often below three tons per hectare, and total production stood at around 42 million tons per harvest year until the early 2000s. Significant increases were observed between 1999/2000 and 2014/2015, when productivity exceeded five tons per hectare and production reached 84 million tons.

“Such growth was mainly driven by the adoption of second-crop corn and the introduction of new production technologies, such as the use of genetically modified crops,” the researcher notes. While technology has boosted production, the emergence of disease outbreaks beginning in 2014/2015 has caused severe declines in national productivity.

Integrated management and good agricultural practices

The corn leafhopper has a high reproductive capacity and spreadability. As it is found throughout the entire Brazilian territory, it is a species that is difficult to manage. Biological control using entomopathogenic fungi, natural enemies of the pest, has proven to be a management alternative that can be combined with chemical control and an important option for the system, given that some populations of the corn leafhopper have already developed resistance to certain classes of insecticides.

Since relying solely on chemical insecticides for control is insufficient, the research recommends adopting a set of practices: 

- Elimination of volunteer corn (plants that sprout during the off-season due to grain loss during harvest and transportation): this breaks the life cycle of the vector and the pathogen.

- Coordinated planting: avoids long planting windows that facilitate the spread of leafhoppers between fields.

- The use of resistant or tolerant cultivars maintains high levels of productivity even under disease pressure.

- Initial management involving the application of chemical and biological controls during the early stages of plant growth (up to the V8 stage): prevents the infection from causing more severe damage.

- Monitoring: This involves constant and coordinated surveillance among neighboring farmers.

Food security and public policy  

The impact of the corn stunt diseases extends beyond the farm gates. Since corn is a key ingredient in the production of animal protein (poultry, pork, and dairy) and biofuels, crop failures drive up consumer prices and affect Brazil’s trade balance.

According to Epagri researcher Maria Cristina Canale, estimating the economic losses in agriculture that are caused by pests and diseases is essential to develop more effective public policies. “With information on disease-related crop losses in corn, it is possible to guide the allocation of funds, advise the agricultural insurance sector, establish planting windows, plan strategies to mitigate the damage caused by the diseases, and evaluate the effectiveness of the practices that are adopted by the agricultural sector,” she concludes.

Source - https://www.embrapa.br