CONTROLE DA CIGARRINHA-DO-MILHO, POR FUNGOS PARASITAS, EM PLANTAS DE Zea mays (var. Saccharata) EM CAMPO

Abstract

The cultivation of Zea mays (var. Saccharata) (Poaceae) in the Brazilian Midwest has real prospects for expansion. However, sweet corn plants are susceptible to viral diseases, as well as mollicutes transmitted by the corn leafhopper, Dalbulus maidis (Hemiptera: Cicadellidae). Recommended control strategies involve synthetic insecticides, cultural control and use of resistant corn varieties. For a number of reasons, such strategies have not shown success as well as acceptance by farmers in Brazil. Parasite fungi may contribute to plant protection against D. maidis due to comparable efficiency with synthetic insecticides. The synergism between silicate compounds and entomopathogenic fungi has been discovered. This can both generate promising results in pest control as well as assist in the performance of mycoinseedicides, under field conditions. The objective of this work was to evaluate the control efficiency (CE%) of the corn leafhopper by foliar spraying of the fungi Beauveria bassiana and Metarhizium anisopliae, as well as the resistance inducer Potassium Silicate (K2SiO3) isolated (or under binary mixtures) under field conditions in Orizona, state of Goiás, Brazil. The isolated treatments (1) Beauveria bassiana (Bb), (2) Metarhizium anisopliae (Ma), (3) Potassium Silicate (SilK) as well as the binary mixtures (4) Bb+SilK, (5) Ma+SilK and (6) Thiamethoxam+Lambda-cyhalothrin were applied via leaf spraying in corn-sweet plants (Tropical Plus® hybrid). Samples of adult corn leafhoppers occurred at 0, 1, 3, 6, 9 and 12 days after application (daa) to calculate CE% between treatments. The Bb fungus showed lower CE% values over time, followed by Bb+SilK and SilK treatments. The Ma+SilK mixture obtained intermediate values for CE%. From the 6th day to the 12th day, the answers presented were more discrepant among the treatments. Ma and the insecticide were higher in terms of CE%, at the end of the experimental period. The reasons for the low CE% of the fungus Bb are discussed, as well as the synergistic potential of the fungi when in binary mixture with the resistance inducer SilK. The present study also emphasizes the potential of the Metarhizium anisopliae fungus for control of D. maidis in sweet corn plants.