Ten tips for managing leafhoppers in corn

Corn leafhoppers (dalbulus maidis), responsible for transmitting the diseases of the Stump Complex, are on the rise in the country, even before the second harvest of the crop is completely sown. Although there is great variability in studies, some show that the incidence of the plague is 280% higher in these first months of 2024, compared to the same period in 2023.

“Another corn crop will be sown and producers in practically all of Brazil continue to face the great challenge of managing the stunting complex, caused by leafhoppers, which includes red, yellow or pale stunting and fine streaked stunting (stripe virus) . These agents have the ability to cause great impact on metabolism and loss of productive potential. And the climate is favoring an increase in incidence in the fields”, says Bayer's market development agronomist, Mateus Torrezan. 

It is worth mentioning that there is no registered treatment for the problem, however, there are good management practices that complement each other with the aim of precisely controlling leafhoppers. To facilitate understanding, see below ten tips on how to efficiently manage leafhoppers dalbulus maidis.

1 - Elimination of voluntary corn (tiguera or guaxo): The producer must eliminate uncultivated cereal plants, originating from grains lost in the harvesting and transport process, which end up germinating not only in agricultural areas, but also on roadsides and flower beds in cities and towns.  

“This volunteer corn ends up serving as a green bridge between one harvest and another, sheltering both the insect and the agents that cause diseases. When feeding on a contaminated plant, the leafhopper can become infected and transmit the three agents together. Therefore, it is important to control tiguera corn as soon as it appears, using graminicidal herbicides”, comments Torrezan. 

2 - Choice of hybrids: This is one of the most important strategies in corn stunt management. Choosing hybrids with a greater degree of tolerance to the stunting complex helps in cases of greater disease pressure during the development of the crop. It is also worth highlighting the importance of always choosing to use certified, quality seeds. 

“A good example of this importance is that since the corn leafhopper became more relevant to cereal crops, Bayer has invested in pest-tolerant technologies. Between 2020 and 2023, we estimate that hybrids launched for this purpose prevented losses of approximately 3,67 million tons of corn, representing US$350 million”, says Piérri Spolti, director of plant pathology and reproduction systems at Bayer. 

3 – Seed treatment: Treating the main crop input is a management practice that can be decisive in keeping adult leafhopper insects away from the newly established corn crop. This management can bring an efficiency of up to 90% at the beginning of sowing, significantly reducing the incidence of the pest, in addition to facilitating management against it later on. 

“The treatment carried out with industrial machines ensures that each seed receives the exact amount of the active ingredient, homogeneously and with greater adherence. In the treatment carried out on the farm, the producer will have to divide the time that already takes place during sowing to carry out the process and will not be able to dedicate himself as he should. Furthermore, the active ingredient is placed in the mixing tank and there is no guarantee that each seed will receive the right amount, creating imperfections that can compromise the individual protection of the plants, in addition to increasing the chance of blocking the planter’s distribution,” he says. Torrezan. 

4 - Distance from already infected plants: Maintaining a safe distance from an already infected crop is extremely important. The leafhopper is a highly migratory pest and tends to migrate from areas with a more advanced stage of development to newer ones. As a result, infection tends to occur earlier, which makes its potential for damage more severe. 

5 - Follow the recommendations regarding planting window and synchronization: Each company, through its studies and research into the development of hybrids, determines the best planting period for each material for each region, with the aim of maximizing the expression of productive potential. Following this positioning, as well as the agroclimatic zoning established for the crop in the region, are fundamental practices for better synchronization of planting and reducing the migration of leafhoppers from older to newer areas. This also makes management strategies more efficient, precisely because they work in a more condensed manner over a short period. 

6 - Monitoring: After corn emergence, crop monitoring must be continuous. Upon detecting the presence of the leafhopper, population management must be initiated through the use of registered insecticides. 

7 – Population management: After the corn emerges and the producer notices the presence of leafhoppers as soon as the first two leaves open, it is time to apply insecticide. An example is Curbix (ethiprole, CAS 181587-01-9, IRAC 2B). Depending on the field evaluation and the agronomist's instructions, there may be a second application, with an interval of at least seven days from the first application, after the two initial leaves are expanded (stage V2). 

Leafhopper nymphs are pests that can hide from conventional insecticides and can generate a population explosion if not controlled. To achieve this, when the corn reaches the V4 stage, if applicable, the producer can start applying another pesticide. An example is Connect (beta-cyfluthrin, beta-cyfluthrin - IRAC 3A + imidacloprid, imidacloprid - IRAC 4A).

“It is necessary to pay attention to the instructions on the leaflet, as contact pesticides, in general, should only be applied twice per crop cycle, while neonicotinoids, which kill nymphs, can only be applied three times per crop”, says Bayer's market development agronomist. 

8 - Attention during harvesting: During the harvesting operation, it is important that the corn is at ideal humidity and that the equipment is properly adjusted. These factors contribute to less loss of ears and grains during the harvesting process. 

9 - Transport of grains: It is important for the producer to make sure that the truck bodies are sealed and properly tarped during transport, thus avoiding loss of grain along the way that could become volunteer plants, hosts for leafhoppers.  

“This can initially affect neighboring properties, and will soon become a green bridge for the producer who lost their grain in transport”, says Torrezan. 

10 - Crop rotation: When planning the property's harvest year, the crop rotation system is essential, avoiding the succession of crops, especially corn on corn. The so-called green corn bridge favors the survival of pathogens and the vector, which always remain in high populations, making control difficult, reducing productivity and increasing costs. 

“Finally, it is worth remembering that as noted above, there is no single and definitive solution to the challenge of the corn stunting complex. Integrated pest management, considering good practices, carried out jointly, is fundamental to promoting satisfactory management, keeping corn crops productive and making this crop so important for Brazilian agriculture viable”, concludes Torrezan.

To ensure safety and effectiveness throughout this process, the producer must seek the guidance of an agronomist and follow the application rules for what is prescribed, observing appropriate climatic conditions, choosing the right application tip, drop coverage, pressure , volume of syrup, among other details. Therefore, adopting measures together is essential to interrupt this cycle.