Corn leafhopper is present in most crops in Mato Grosso

The corn leafhopper (Dalbulus maidis) is one of the pests that causes the most concern to producers throughout Brazil. In Mato Grosso, it is a problem present in most corn-producing regions and, in this second harvest in progress, the crops have had a high population of the insect since the plants emerged, mainly in the mid-northern region of the state. According to researcher and doctor in entomology from the Mato Grosso Agricultural Research Support Foundation (MT Foundation), Lucia Vivan, the applications were carried out, but the population remained in the area.

The presence of sooty mold is also being observed, but, on the other hand, the occurrence of stunting is lower compared to the 2020/21 harvest, according to the specialist. “This may be due to more adequate control carried out by producers and also the use of hybrids tolerant to the stunting complex. However, it is important to continue monitoring the areas that are in the reproductive stage, as symptoms may occur later”, highlights Lucia.

The researcher recalls that in the first harvest plantings, the population was larger from the end of October 2021, growing and remaining in the area. And the symptoms of stunting were practically null or did not express themselves, as the pest attack occurred in more advanced periods of development and applications were made to the target.

Challenge

Understanding the dynamics of the infectious leafhopper population within the production system is today the biggest challenge for corn producers. The entomologist explains that the insect can shelter in grassy areas, pastures, survive in tigueras corn, thus maintaining the population in areas sown with corn. Furthermore, effective control is also challenging due to the insect's behavior, which moves a lot between areas and can disperse over long distances. “They move in flocks and, in this way, the population disperses over long distances”, explains the researcher.

Research advances

In the 21/22 harvest, the MT Foundation began monitoring the population in the corn area since the first harvest, continuing with the planting of the second harvest. The objective of this work was to identify the beginning of colonization by the leafhopper and how the population remained in areas with corn afterwards, as well as to understand the stunting complex over time. Furthermore, the MT Foundation develops work with chemical and biological control, evaluating the mortality and efficiency of products, and also protection in relation to the stunting complex.

Evaluations of different corn hybrids in relation to tolerance to the stunting complex in various regions of Mato Grosso complete the work on the leafhopper. One of the tests is installed at the Learning and Diffusion Center (CAD) Médio Norte, the institution's research area in Sorriso.

Felipe Araújo, researcher at Fundação MT, points out that with the experiment, it is possible to evaluate which hybrids perform best in the conditions they are in, and the response regarding the stunting complex. “We are looking for an answer closer to what the producer needs, a severity metric on productivity, that is, how much each material loses in productive potential to the stunting complex and not just how many plants have shown symptoms of one disease or another”, explains.

In the last harvest, evaluations from this trial indicated levels of productivity reduction from 1% with the most tolerant material, to 17% with the most sensitive material. According to the researcher, these data may vary depending on when the infectious leafhopper population enters the plot, as well as population pressure. “Responses like these are subject to further study to understand whether there is repeatability of the data, even under different conditions of exposure of these materials to the stunt complex”, he concludes.

Necessary management

Leafhopper management is made up of several tools that must be carried out together, such as: destruction of corn tiguera plants; good harvest of corn areas in order to avoid sowing; seed treatment; use of chemical and biological products from the beginning of crop development, and maintain applications until the V8-V10 stages. In addition to these tools, applications on borders can also be a strategy due to the displacement of the insect from other areas.

As for cultural measures, experts recommend avoiding late planting, avoiding staggering planting in nearby areas, having a more concentrated planting window; crop rotation; do not plant corn in areas with high leafhopper populations and incidence of stunting complex; use of hybrids tolerant to the stunting complex; and carry out constant monitoring in the area.