Agentes de controle para o manejo de molicutes na cultura do milho

Abstract

Maize (Zea mays) is one of Brazil's main agricultural crops, widely used as a source of human and animal food. However, the crop's productivity has been impacted by the infestation of the corn leafhopper Dalbulus maidis (Hemiptera: Cicadellidae), a vector of pathogens responsible for the diseases that make up the Corn Blight Complex. This damage highlights the need for effective management strategies to control the pest. The aim of this study was to evaluate, under field conditions, the effectiveness of products based on the entomopathogenic fungi Beauveria bassiana and Cordyceps javanica as components of the integrated management of D. maidis. The experiments were conducted in a network, at cooperative experimental stations located in the municipalities of Campo Mourão, Cafelândia, Assaí and Floresta, in the state of Paraná, and in Sete Lagoas, Minas Gerais, during the second harvest of 2024. The treatments tested consisted of six combinations of chemical (methomyl and acephate) and biological (Beauveria bassiana and Cordyceps javanica) products, applied from the V3 stage of the AS 1844 hybrid In all the treatments, acephate was applied at the V1 and V2 stages to control the green-bellied stink bug (Diceraeus melacanthus). Control was established using plants treated exclusively with products aimed at the bug. The severity of the blights was assessed using rating scales, and corn yield was determined based on the ratio between the quantity of grains harvested and the area cultivated (Kg/ha). In addition, the molecular detection of the mollicutes “Candidatus Phytoplasma asteris” and Spiroplasma kunkelii was carried out via specific PCR in leaf and stalk samples. The joint analysis of the experiments indicated that the treatment of the plants with methomyl combined with Beauveria bassiana (T3) was the most efficient, as it showed the lowest severity score for blight (2.40), which corresponds to less than 25% of leaves showing symptoms of the disease. However, treatment T3 recorded the highest rate of molecular detection of the mollicutes, with 80% of the samples showing DNA from the pathogens. Treatment T7 (without application) showed the highest yield, reaching 8147.5 kg/ha. The results indicate that the use of entomopathogenic fungi can contribute to the control of D. maidis. However, there were no statistically significant differences between the chemical and biological treatments in terms of productivity.