The Santa Catarina Corn Monitor Program identified a low incidence of corn leafhoppers captured in the week of February 26th to March 4th. “This means that the producer adopted control measures”, ponders Maria Cristina Canale Rappussi da Silva, researcher at Epagri/Cepaf responsible for analyzing the infectivity of captured insects. However, the insects analyzed showed the potential to infect plants with red stunt and stripe virus diseases.
According to Maria Cristina, the average number of insects collected is around 43%. Palmitos was the place with the fewest insects captured during the week, a total of 11. The place with the most infestation was Lages, with 118 insects in the trap.
“Currently, I consider the average incidence of insects in the trap to be very low, because it was previously higher”, evaluates Maria Cristina. She highlights a decrease in insects collected in the last three or four weeks of monitoring. For the researcher, this indicates that the farmer may be carrying out some management up to the plant's eight to ten leaf stage.
The monitoring carried out by the Program evaluates the infectivity of the corn leafhopper by three phytopathogens: red stunt phytoplasma, pale stunt spiroplasma and stripe virus. These diseases are capable of substantially compromising grain harvests. In the week evaluated, the Program identified more than 50% of the samples with phytoplasma and 80% to 90% with the virus, while spiroplasma was not so present.
“The infectivity of the pale stunt spiroplasma was not very high in the week of analysis, which is surprising, because in past monitoring we had much higher infectivity than in this harvest”, reports the researcher. On the other hand, the red stunt phytoplasma, which has always been present, has shown a high prevalence of infectivity in the insects evaluated. Maria Cristina also warns that the infectivity of insects with the stripe virus has increased substantially over the past six or seven weeks.
From now on, the monitoring team expects an increase in the incidence of insects in the traps. This is because the corn has already entered the reproductive phase and is tall, which makes it difficult for the farmer to enter the field to apply insecticide.
Added to this is another concern. As the corn is already mature and filling the grains, producers are already planning the harvest. Given the high field infectivity resulting from red stunt and stripe virus pathogens, the risk is that there will be loss of grains during harvesting and transport of the crop, which can give rise to volunteer corn, also known as tiguera or raccoon.
This corn, which grows spontaneously from lost seeds, can become what researchers call a green bridge, that is, a shelter for infected leafhoppers to remain alive until the next harvest. This would increase the possibility that the next harvest will begin with significant infectivity, to the point of causing an epidemic. To avoid this situation, Maria Cristina reinforces the warning to farmers, so that they can avoid grain loss during harvesting and transportation as much as possible.
Monitoring of the corn leafhopper in Santa Catarina continues until the end of April in ten points: Águas de Chapecó, Água Doce, Campo Erê, Caxambu do Sul, Guatambu, Faxinal dos Guedes, Lages, Palmitos, Videira and Canoinhas.
At the beginning of 2021, the Action Committee Against Corn Leafhopper and Stunting Complex was created, bringing together members from the following institutions: Epagri, Udesc, Cidasc, Ocesc, Fetaesc, Faesc, CropLife Brasil and the State Secretariat for Agriculture and Livestock . This committee implemented the Monitora Milho SC Program, with the objective of monitoring the populations and infectivity of the corn leafhopper in the State, through monitoring points installed in crops in Santa Catarina.
The information generated by the Monitora Milho SC Program helps farmers and technicians to make decisions about management and verify the efficiency of the strategies adopted. Within the properties, Epagri provides guidance on control measures, such as choosing corn varieties that are tolerant to stunting, using treated seeds and reducing the sowing window. Another important action is the campaign to eliminate voluntary corn.
In the battle against the corn leafhopper, Epagri also made the Monitora Milho SC Application available, available for free download on cell phones using the Android operating system. The tool gives access to a map of Santa Catarina with the points where crop monitoring is carried out. In this area, it is possible to observe the population level of the corn leafhopper in different regions of Santa Catarina.
The application also allows you to access a table with information about the municipalities, with management recommendations based on the values presented in each location. The tool shows the evolution of the infectivity of the samples, with updated information about the crops monitored in different municipalities in Santa Catarina.
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