Metarhizium pingshaense photolyase expression and virulence to Rhipicephalus microplus after UV-B exposure.

The current study examined the impact of ultraviolet (UV)-B radiation in Metarhizium pingshaense blastospores' photolyase expression and their virulence against Rhipicephalus microplus. Blastospores were exposed to UV under laboratory and field conditions. Ticks were treated topically with fungal suspension and exposed to UV-B in the laboratory for three consecutive days. The expression of cyclobutane pyrimidine dimmers (CPDs)-photolyase gene maphr1-2 in blastospores after UV exposure followed by white light exposure was accessed after 0, 8, 12, 24, 36, and 48 h. Average relative germination of blastospores 24 h after in vitro UV exposure was 8.4% lower than 48 h. Despite this, the relative germination of blastospores exposed to UV in the field 18 h (95.7 ± 0.3%) and 28 h (97.3 ± 0.8%) after exposure were not different (p > 0.05). Ticks treated with fungus and not exposed to UV exhibited 0% survival 10 days after the treatment, while fungus-treated ticks exposed to UV exhibited 50 ± 11.2% survival. Expression levels of maphr1-2 8, 12, and 24 h after UV-B exposure were not different from time zero. Maphr1-2 expression peak in M. pingshaense blastospores occurred 36 h after UV-B exposure, in the proposed conditions and times analyzed, suggesting repair mechanisms other than CPD-mediated-photoreactivation might be leading blastospores' germination from 0 to 24 h.

Performance of Metarhizium anisopliae and Its combination with deltamethrin against a pyrethroid-resistant strain of Boophilus microplus in a stall test.

The use of the entomopathogenic fungus, Metarhizium anisopliae, to control ticks is a promising alternative to chemical acaricides, but both chemical and biological products could also work together in an integrated management. The current study evaluated the performance of M. anisopliae and its combination with deltamethrin to control a Boophilus microplus strain resistant to pyrethroid. Calves were held in individual pens and artificially infested with B. microplus. They were treated with an aqueous conidial suspension of M. anisopliae, a deltamethrin solution, or both fungus and deltamethrin combined. After treatment, engorged females that naturally dropped off from calves were counted daily and evaluated in the laboratory. The mean mortality rate was 32.57% in the groups treated with M. anisopliae, 38.58% in those groups treated with deltamethrin, and 30.92% in those treated with fungus and chemical combined. Additionally, ticks that dropped off from calves after 2 days had a lower nutrient index (NI) and egg production index (EPI) than those that dropped off at a later day after treatment. This indicates that M. anisopliae may reduce B. microplus population only for a few days after treatment when a simple aqueous conidial suspension was used.

Virulence of Metarhizium anisopliae to eggs and immature stages of Stomoxys calcitrans.

Stomoxys calcitrans control is primarily based on the use of chemical products; however, new methods for control have been investigated. Biological control has been proposed as a promising alternative to traditional chemicals. The current study evaluated three methods in vitro to treat S. calcitrans eggs with the fungus Metarhizium anisopliae and assessed the virulence of this fungus to immature stages of this fly. In the first method of egg exposure, eggs were immersed in conidial suspensions and transferred to Petri plates with high humidity. A high mortality was observed in both treated and control groups. In the second method, the eggs were transferred to rearing medium right after immersion in conidial suspensions; the suspensions with highest conidial concentrations, 10(7) and 10(8) conidia mL(-1), caused 96.25% and 100% mortality, respectively. In the third method, the eggs were sprayed with conidial suspensions on the rearing medium. A high mortality was observed at 10(7) and 10(8) conidia mL(-1), 78.3% and 100%, respectively. The second method had the lowest mortality in the control group and was considered the most useful method for evaluating the effect of entomopathogenic fungi on S. calcitrans eggs. While eggs were very susceptible to M. anisopliae infection, larvae and pupae were not.

[Evaluation of the biological control potential of Metarhizium anisopliae toward Boophilus microplus in pen trials]. / Avaliação do potencial de controle biológico do Metarhizium anisopliae sobre Boophilus microplus em teste de estábulo.

The aim of the present study was to evaluate the capacity of the fungus Metarhizium anisopliae to control Boophilus microplus tick in pen trials. Infested calves were held in individual pen and treated with fungus suspension through aspersion bath. The results were evaluated based on ticks' mortality rate for 28 days after treatment, and on the analysis of biology of tick's samples which were transferred to an incubation chamber. It was reported 33% of mortality during the total period analyzed, and the production of eggs and nutritional rates were decreased only for a short period after treatment.

Avaliação do potencial de controle biológico do Metarhizium anisopliae sobre Boophilus microplus em teste de estábulo / Evaluation of the biological control potential of Metarhizium anisopliae toward Boophilus microplus in pen trials

Avaliou-se por meio de um teste de estábulo a capacidade de Metarhizium anisopliae em controlar o carrapato Boophilus microplus. Foram realizados tratamentos em bovinos estabulados, utilizando este fungo aplicando-se suspensão conidial em banhos por aspersão. Os resultados foram obtidos pelo percentual de mortalidade de carrapatos durante 28 dias após o tratamento e pelos índices biológicos após incubação destes em câmara climatizada. Constatou-se 33 por cento de mortalidade no período total observado, sendo o índice de produção de ovos e índice nutricional reduzidos somente em um curto período após o tratamento.

The aim of the present study was to evaluate the capacity of the fungus Metarhizium anisopliae to control Boophilus microplus tick in pen trials. Infested calves were held in individual pen and treated with fungus suspension through aspersion bath. The results were evaluated based on ticks' mortality rate for 28 days after treatment, and on the analysis of biology of tick's samples which were transferred to an incubation chamber. It was reported 33 percent of mortality during the total period analyzed, and the production of eggs and nutritional rates were decreased only for a short period after treatment.