Adapar intensifies monitoring of corn stunting in Paraná

The occurrences of the corn leafhopper, the vector agent for diseases called stunt complex, have been a challenge for rural producers in the state. These diseases harm the development of ears and cause reduced productivity. Monitoring carried out by the Agricultural Defense Agency of Paraná (Adapar), combined with research and guidance for producers, has helped to reduce the problem.

Among the generally recommended management strategies is the use of cultivars with greater genetic tolerance to stunting.

“However, even tolerant materials, when exposed to high population pressures of contaminated corn leafhoppers, show symptoms of stunting”, explains Adapar's Plant Health Manager, Renato Young Blood. Thus, controlling and monitoring insect dynamics has proven to be a more effective resource.

In September this year, Adapar installed traps on rural properties in several regions of the state to quantify the presence of leafhoppers. Since then, trap replacements have been carried out weekly, as well as samples being sent for analysis to the Marcos Enrieti Diagnostic Center – CDME, an Adapar laboratory. There are 40 monitoring points with high and low presence of infestation, resulting, so far, in 374 analyzes and 5.390 corn leafhoppers collected.

Based on the analyses, Adapar technicians observed that, until the second half of November, in high pressure points, the corn leafhopper population does not increase significantly.

“This is due to the chemical control carried out by producers during the development of corn, mainly until the beginning of the reproductive stage, which is the period most susceptible to these diseases”, explains Ralph Rabelo Andrade, who is compiling and analyzing the monitoring results.

With the beginning of the corn reproductive period, chemical control decreases and the population tends to increase until harvest. In monitored areas of low pressure there is also an increasing trend from the beginning of December, probably stimulated by the increase in average temperatures, according to technicians.

For corn leafhoppers to transmit these diseases, they must be infected by pathogens called mollicutes (Spiroplasma or Phytoplasma) or by viruses that affect corn crops. Around 63% of the traps monitored by Adapar contained leafhoppers, 16% of which were infected with Fitoplasma, 5% with Spiroplasma and 4% with both.

“Thus, the elimination of volunteer plants by rural producers, which is the initial source of contamination in commercial crops, is one of the most important practices for crop health”, advises Young Blood.

Paraná is the second largest corn producer in the country, behind Mato Grosso. According to the Department of Rural Economy (Deral) of the Secretariat of Agriculture and Supply, production of the first harvest is estimated at 3,73 million tons on 383,9 thousand hectares. The first production estimate for the second harvest, released last week, predicts, under ideal weather conditions, the production of 15,42 million tons on 2,64 million hectares.

Management strategies can help producers produce corn crops that meet production expectations and crop profitability.

“With the increase in the corn leafhopper population from December onwards in low-pressure areas, and from the reproductive phases of corn in high-pressure areas, the tendency is for the planting of the second crop to begin with a large presence of these insects, which reinforces the importance of adequate management and permanent monitoring of crops”, says the coordinator of the Pest Prevention and Control program in Agricultural and Forestry Crops at Adapar, Marcílio Martins Araújo.

According to him, monitoring, research, guidance for producers regarding management actions and the choice of tolerant materials have guaranteed good results. “Combining these strategies is extremely important and can provide greater security for producers in Paraná in obtaining a productive and profitable harvest.”