Banca de DEFESA: LAURA NOBREGA MEIRELLES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LAURA NOBREGA MEIRELLES
DATE: 29/01/2026
TIME: 09:00
LOCAL: UFRRJ, IV, DPA
TITLE:

Development of microparticles with Metarhizium conidia: characterization, stability and application in Rhipicephalus microplus control

KEY WORDS:

entomopathogenic fungi, ionic gelation, cattle tick

PAGES: 80
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Parasitárias de Animais
SUMMARY:

Entomopathogenic fungi are a sustainable alternative for the biological control of Rhipicephalus microplus, particularly given the emergence of resistance to chemical acaricides. The production of microparticles by ionic gelation for encapsulating propagules is a promising strategy, as it allows polymers and adjuvants to be combined to protect the fungus and improve its shelf life. This study aimed to develop microparticles containing Metarhizium anisopliae s.l. CG 148 conidia encapsulated with different combinations of sodium alginate (A), pectin (P), glycerol (G), and chitin (Q). The encapsulation efficiency and the influence of chitin addition on conidia production were investigated, and the particles were analyzed for size distribution, morphology, structure, shelf life, UV-B tolerance, thermotolerance, and efficacy in controlling R. microplus in the laboratory and semi-fileld conditions. The ionic gelation efficiency was assessed by quantifying and verifying the viability of the encapsulated conidia. To investigate the effect of chitin on propagule production, the sporulated conidia of the microparticles incubated in culture medium were quantified. Formulations containing chitin (AQ, APQ, AGQ e APGQ) were used in subsequent experiments. Size distribution was analysed using ImageJ, morphology was analysed using stereoscopic and scanning electron microscopy, and infrared spectroscopy (FTIR) was performed. The microparticles and the non-encapsulated conidia (NEC) were stored for one and two months at room temperature and in a refrigerator. For tolerance tests, samples were exposed to UV-B radiation (6.0 kJ m⁻²) and heat (45 °C for four hours). The efficacy of the fungal microparticles in controlling ticks was evaluated in laboratory and semi-field settings. Encapsulation reduced the concentration of conidia by an average of 2.5× without compromising viability. Compared to formulations without chitin, the AQ, APQ, AGQ and APGQ particles showed increases of 60.26%, 84.77%, 37.72% and 54.84%, respectively, in conidia production. The microparticles exhibited spherical shapes with more homogeneous (APQ and APGQ) or heterogeneous (AQ and AGQ) surfaces. The average diameter of the AQ, APQ, AGQ and APGQ microparticles was 1,338 µm, 1,459 µm, 1,244 µm and 1,367 µm, respectively. FTIR analyses suggested physical interactions between the polymeric matrix and the fungus. NEC exhibited greater germination than the fungal microparticles under both storage conditions. Refrigerated storage was more efficient in maintaining microparticle viability than ambient storage. NEC germination decreased after exposure to UV-B radiation (59.08%) and heat (0.19%), compared to AQ (98.59% and 71.74%), APQ (95.48% and 93.87%), AGQ (94.37% and 68.18%) and APGQ (97.95% and 75.5%), respectively. In the laboratory, the microparticles reduced biological parameters and the survival of engorged females compared to the control group, with no difference observed in comparison to the NEC group. In semi-field conditions, AGQ reduced the number of larvae by 59.5% compared to the untreated group, while APQ was ineffective. These findings reinforce the potential of fungal microparticles as an innovative approach to controlling this tick, adding technological value to a final product that offers practical advantages for field use, such as easily application and greater stability.

COMMITTEE MEMBERS:
Interna - 2860277 - ISABELE DA COSTA ANGELO
Interno - 1296670 - WENDELL MARCELO DE SOUZA PERINOTTO
Externa ao Programa - 387922 - VANIA RITA ELIAS PINHEIRO BITTENCOURT - UFRRJExterna à Instituição - VALESCA HENRIQUE LIMA - UFG
Externo à Instituição - JHONES LUIZ DE OLIVEIRA
Externo à Instituição - EVERTON KORT KAMP - UFG
Externa à Instituição - EMILY MESQUITA DA SILVA - UFRRJ