ALTERNATIVES FOR THE CONTROL OF THE TICK Rhipicephalus (Boophilus) microplus BASED ON Bacillus thuringiensis

• DOI: https://doi.org/10.22533/at.ed.813472416109

• Palavras-chave: microbial control, spore-crystal complex, ovicidal effect, cattle tick.

• Keywords: microbial control, spore-crystal complex, ovicidal effect, cattle tick.

• Abstract:

  Microbial control of the tick Rhipicephalus microplus has focused on evaluating toxicity to adults and larvae, with a response time varying from 3 to 10 days to cause mortality in ingested ticks, depending on the species of bacteria used. However, during this period, ticks may oviposit as a defense mechanism. Therefore, the objective of this work was to evaluate the ixodicidal effect of the spore-crystal complex of Bacillus thuringiensis strain GP543 for the control of R. microplus ticks. Mortality and hatching inhibition percentages were evaluated in immersion bioassays with freshly ingested female ticks with concentrations of 50 and 300 µg-mL-1 of the spore-crystal solution and distilled water as a control. The bioassay was performed under a completely randomized experimental design, each experimental unit contained 24 individuals, individually distributed in 24-well cell culture plates, with 4 replicates. The highest percentage of mortality in the treated ticks was recorded at 14 days, at this time a mortality of 51.7% was observed at the lowest concentration used (50 µg-mL-1 ) and a higher percentage of mortality (75.0%) when the concentration of the spore-crystal complex was increased to 300 µg-mL-1 . Regarding the effect on hatching inhibition, values of 85.2% (50 µg-mL-1 ) and 89.2% (300 µg-mL-1 ) were obtained, which, although statistically equal, are significant values. These results demonstrate that the spore-crystal complex of B. thuringiensis strain GP543 is able to reduce oviposition and hatching of ixodicide-resistant ticks.