Controle microbiano do ácaro praga: mononychellus tanajoa bondar, 1938 acari: tetranychidae em condições de laboratório e semi-campo

Abstract

Mononychellus tanajoa is the main pest mite of cassava crops. This mite causes greateconomic losses and decreases in production yield. Microbial control is a promising alternative for reducing the population of the cassava green mite. This study aimed to evaluate the efficacy of different commercial formulations of entomopathogenic fungi (Beauveria bassiana and Metarhizium anisopliae) in controlling the mite M. tanajoa. Laboratory bioassays were performed in a completely randomized design (CRD) with 10 treatments and 50 replicates for each concentration. The treatments consisted of M. anisopliae with solutions of 1%, 2.5% and 5%, B. bassiana, 1%, 9% and 27% and M. anisopliae+ B. bassiana, 1%, 2.5% and 5% and the control treatment (distilled water). In each replicate, a cassava leaf disc was immersed for 10 seconds in the tested solutions and, after drying, was infested with 10 adult female mites. The experimental units were maintained in B.O.D., at 25 ± 2 oC, 71 to 87% RH and 12h photophase. Mortality assessments occurred during 24, 48, 72 and 96 hours after the experiment was set up. For the semi-field bioassay, the experimental design adopted was a Randomized Block Design (RBD), with seven treatments and seven blocks, containing fourteen plants per block and two plants per fungal solution treatment, using the concentrations tested in the laboratory experiment that were most efficient (Beauvel®sc: 9% and 27%; Mesopel Mix®sc: 2.5% and 5%; Metarhizium Hizobio: 2.5% and 5%; and the control. Mortality assessments occurred after 15 applications of the solutions. Confirmation of mite mortality by fungal-based products was determined in Potato Dextrose Agar culture medium (PDA medium). The results were subjected to regression analyses and their means compared by the Tukey test P ≤ 0.05 through the SAS® Software Program and Probit to determine the LC50 and TL50. In the laboratory test, the The Metarhizium Hizobio product was the most efficient and caused mortality of 86.5% to 99% of the M. tanajoa mite. Mesopel Mix®sc caused mortality of 65% to 75% and Beauvel®sc, of 50% to 75%, demonstrating lower efficiency. The tested products presented LC50 of 0.44 and TL50 of 0.39 for Metarhizium Hizobio, LC50 of 0.01 and TL50 of 2.75 for Beauvel®sc and LC50 of 0.02 and TL50 of 3.07 for Mesopel Mix®sc. In the semi-field bioassay, the Beauvel®sc product with a concentration of 9% obtained the best mortality performance, followed by Metarhizium Hizobio at concentrations of 2.5% and 5%. The pathogenic fungi tested showed promise for the biological control of the M. tanajoa mite, representing a safe and effective alternative to pesticides. The product Metarhizium Hizobio causes the epizootic in M. tanajoa. The products Mesopel Mix®sc and Beauvel®sc control M. tanajoa. Keywords: Pathogenic fungi; cassava; epizootic.