Embrapa and CropLife Brasil sign a commitment to research on corn stunting

With the aim of developing applied studies to support management strategies for the high incidence of damage caused by stunting and promoting integrated management of the corn leafhopper (Dalbulus maidis), in seed and corn grain production areas, Embrapa and CropLife Brasil have just announced a technical cooperation agreement, during the event celebrating the company's 49th anniversary, held on 27/04/2022 at its Headquarters in Brasília (DF).

In 2021, the Gross Value of Agricultural Production (VBP) reached R＄ 1,129 trillion, with emphasis on the results in corn crops (R＄ 125,2 billion), demonstrating the economic importance of the crop for Brazil (MAPA, 2022) [1]. The increase in corn production, to meet the growing demand for this cereal, as well as the environmental conditions that allow the cultivation of two or more crops of the same crop in several regions of Brazil, contribute to the presence of corn plants in the field. whole year, whether cultivated or tiguera, and creating a favorable environment for the increase in the corn leafhopper population and, consequently, the stunt complex.

According to Embrapa[2], the stunt complex affects the development of corn plants and can cause losses of 70% in the production of the diseased crop. The occurrence of stunting and population levels of the corn leafhopper has been increasing in several states in Brazil, mainly since the 2015/2016 harvest, with larger outbreaks identified in agricultural regions located in Bahia, Goiás, Minas Gerais, São Paulo, Mato Grosso do Sul and Paraná.

The corn leafhopper is responsible for transmitting mollicutes (Spiroplasma kunkelli - pale stunting - and Phytoplasma -- Maize bushy stunt phytoplasma - red stunt) and corn stripe virus (Maize Rayado Fino Virus - MRFV). Although the occurrence of stunting and corn leafhoppers is not new to farmers, the increase in geographic scope and the size of losses are worrying, requiring a greater level of knowledge about the problem, to improve actions to disseminate technology and the adoption of good agricultural practices. For Celso Moretti, president of Embrapa, “the project reinforces Embrapa's commitment to establishing partnerships with the private sector to solve problems of great impact on Brazilian agriculture based on synergy of public-private investments, increasing efficiency, efficiency and effectiveness of the innovation process in the field”.

Embrapa's work plan with CropLife Brasil foresees the carrying out of twenty research activities and the development of new studies, such as the creation of a broad national monitoring network; evaluating the efficiency of chemical and biological insecticides for controlling the corn leafhopper; determining the stability of resistance of corn genotypes to stunting; the development of rapid and more economical tests to detect mollicutes in the corn leafhopper; as well as the organization of technical events to disseminate knowledge. The project also foresees carrying out several studies to cover gaps in knowledge in relation to the pathosystem, stunting, leafhoppers and corn plants. Coordination will be the responsibility of Embrapa Cerrados (DF), with the participation of Embrapa Genetic Resources and Biotechnology (DF) and Embrapa Milho e Sorgo (Sete Lagoas, MG).

Fourteen companies associated with CropLife Brasil, from the areas of biotechnology, seeds, chemical pesticides, biological products and biotechnology, came together to sponsor the project: Basf, Bayer, Corteva, FMC, Helix, ISK, Koppert, KWS, LongPing, Limagrain, Ourofino , Symbiosis, Sumitomo and Syngenta. For Christian Lohbauer, executive president of the entity, the partnership with Embrapa will prioritize applied research and deepen knowledge about measures to control stunting, in addition to accelerating the dissemination of good agronomic practices. “The expansion of planted areas and the growing phytosanitary problems in corn require that a set of actions be adopted by the production chain, including the development of public policies to regulate the implementation of good agricultural practices”, explains Lohbauer.

Good management practices

No measure taken in isolation is effective in managing stunting, since the severity of these diseases is the result of the interaction between the insect vector (D. maidis), the pathogens (spiroplasma and phytoplasma) and the host plant (corn) .

As these are diseases that are spread through an insect vector, it is not possible to determine the level of economic damage, as the severity of the disease will depend on how many leafhoppers carry mollicutes in a population and not necessarily on the size of the population. leafhoppers. Thus, the (reactive) decision to control the insect vector is currently made based on its presence or absence. Preventive management measures are the most recommended, aiming to reduce the leafhopper population and mollicute inoculum sources (availability of corn over time).

While new research advances, Embrapa and CropLife Brasil listed 10 measures that must be adopted to reduce the corn leafhopper population, the multiplication of mollicutes and minimize the risks of high incidence of stunting on properties and at a regional level.

1. Eliminate volunteer corn (tiguera) and keep the field weed-free;
2. Do not sow corn next to adult crops showing stunt symptoms;
3. Use cultivars with greater genetic tolerance to stunting;
4. Use certified seeds treated with registered insecticides;
5. Synchronize the sowing period at the beginning of the recommended season in the region;
6. Monitor the presence of the leafhopper between phases VE-V8 and apply registered insecticides to reduce the vector population as much as possible;
7. Rotate the modes of action to avoid the leafhopper’s resistance to insecticides;
8. Control the quality of the harvest and avoid the loss of ears and grains;
9. Correctly transport harvested corn and avoid losing grain on the roads;
10. Rotate crops and avoid successive sowing of grasses.