Encapsulation of entomopathogenic fungal conidia: evaluation of stability and control potential of Rhipicephalus microplus

Author(s)

Meirelles, Laura Nobrega ; Mesquita, Emily ; Correa, Thais Almeida ; Bitencourt, Ricardo de Oliveira Barbosa ; Oliveira, Jhones Luiz ; Fraceto, Leonardo Fernandes ; Camargo, Mariana Guedes ; Bittencourt, Vania Rita Elias Pinheiro

• Document type: Journal article
• Source: TICKS AND TICK-BORNE DISEASES; v. 14, n. 4, p. 10-pg., 2023-04-25.

Abstract

The use of chemical acaricides is the primary strategy to control tick infestations. Nonetheless, chemical resistance in ticks has been reported. Thus, complementary methods such as biological control using entomopathogenic fungi (EPF) have been investigated. EPF, although efficient, have their viability compromised when applied under natural conditions, which indicates that formulation development is essential. Some researchers have demonstrated the efficacy of ionic gelation in protecting EPF against deleterious abiotic factors. In the present study, we conducted the ionic gelation technique to encapsulate Metarhizium anisopliae (Metschn.) Sorokin (Hypocreales: Clavicipitaceae) conidia in 2% (EC 2%) and 3% (EC 3%) sodium alginate. Next, the quantity and viability of encapsulated conidia (EC) were determined. The morphology of particles was characterized by using Scanning Electron Microscopy (SEM). EC and non-encapsulated conidia (NEC) were stored at room temperature (26.8 degrees C) and in the freezer (-11.9 degrees C) to shelf-life testing. For UV-B irradiance tolerance and thermotolerance tests, EC and NEC were exposed to UV-B (6.0 or 8.0 kJ m - 2) and heat (42 oC). In addition, biological parameters of Rhipicephalus microplus Canestrini (Acari: Ixodidae) engorged females exposed to EC were evaluated. The particles presented a spherical shape, more homogeneous (EC 2%) or heterogeneous (EC 3%). Encapsulation decreased (4.8x) the conidial concentration and did not affect their viability. On the other hand, encapsulation increased the shelf life of conidia at room temperature as well as their UV-B tolerance and thermotolerance (6 h). The fungal particles decreased the biological parameters of females more significantly than the NEC. As far as we know, we reported for the first time the use of the ionic gelation to encapsulate entomopathogenic fungi toward controlling R. microplus. (AU)

• FAPESP's process: 18/21142-1 - Encapsulation of Bacillus thuringiensis (Bacillales: Bacillaceae) in polymeric microparticles and association with nanoencapsulated chemical agent: evaluation of biological activity and mechanisms of action
• Grantee: Jhones Luiz de Oliveira
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 17/21004-5 - Agriculture, micro/nanotechnology and environment: from evaluation of the mechanisms of action to studies of transport and toxicity
• Grantee: Leonardo Fernandes Fraceto
• Support Opportunities: Research Projects - Thematic Grants