Banca de DEFESA: SARAH RUTH ALVES DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : SARAH RUTH ALVES DA SILVA
DATE: 21/03/2025
TIME: 14:00
LOCAL: https://meet.google.com/rby-sfvy-gbr
TITLE:

Rosemary essential oil (Lippia grata Schauer): insecticidal and repellent potential against Chrysomya megacephala in laboratory conditions

 

KEY WORDS:

Bioinsecticide. Natural insecticide. Natural repellent.

PAGES: 70
BIG AREA: Ciências Biológicas
AREA: Parasitologia
SUBÁREA: Entomologia e Malacologia de Parasitos e Vetores
SUMMARY:

5. Resumo em inglês (abstract):
The species Chrysomya megacephala (Fabricius, 1794) is notable for its wide distribution and medical-veterinary importance, serving as a mechanical vector for various pathogens. The use of synthetic insecticides is the primary method of controlling these insects, but it has led to the development of resistance and environmental problems. Consequently, there has been an increased interest in research into alternative control strategies, including the use of essential oils. Literature records the insecticidal potential of the species Lippia grata (alecrim-do-mato) against some insects of medical significance, but its application in combating muscoid diptera, such as C. megacephala, remains largely unexplored. This study aimed to evaluate the insecticidal and repellent potential of L. grata essential oil against C. megacephala. Bioassays were conducted under laboratory conditions, using L. grata essential oil obtained through hydrodistillation. The insecticidal potential was tested using concentrations of 3.125%, 6.25%, 12.50%, 15%, 17.50%, 25%, 50%, 75%, and 100% on adults, and 12.5%, 25%, 50%, 75%, and 100% on larvae, with topical applications (3 µL) in both tests. For the repellent bioassays, concentrations of 6.25%, 12.5%, 25%, 50%, and 100% were used, administered (1 mL) onto filter paper within a custom-designed system. In the adult insecticidal bioassay, mortality was observed at various time intervals: 15, 30, 45, 60, 120 minutes, 24, and 48 hours. For the third-instar larval insecticidal assays, observations were made 24 and 48 hours post-application. Repellency assays involved analyses every 10 minutes, totaling three observations (30 minutes). The lethal and repellent concentrations for 50% (LC50 and RC50) and 90% (LC90 and RC90) were calculated using Probit analysis. Carvacrol (51.4%) was identified as the major component of the oil. Adulticidal bioassays revealed dose-dependent mortality with significant differences across concentration ranges (p<0.001), where 100%, 75%, 50%, and 25% doses exhibited the highest lethality. The LC50 and LC90 for adults were 6.45% and 22.61%, respectively, after 48 hours. Larvicidal bioassays showed significant differences between concentration ranges (p<0.0051), with the 100% oil concentration having a significantly different effect (p<0.005) on immature mortality. Other concentration comparisons showed no significant differences. The LC50 and LC90 for L3 larvae were 25% and 927%, respectively, after 48 hours. In repellency bioassays, the RC50 was 31.76%, and the RC90 was 115.51%. The results demonstrated that the essential oil was effective as an insecticide, with dose-dependent mortality indicating high toxicity to C. megacephala adults even at relatively low concentrations. The oil also exhibited larvicidal activity, though less potent than against adults. The 100% concentration was significantly more effective than others, suggesting that higher doses are necessary for satisfactory larval control. Furthermore, the assays present promising results regarding the oil's potential as a natural repellent against C. megacephala. Thus, this study indicates that the oil may be a promising alternative to synthetic insecticides for controlling this insect of medical-veterinary importance.

 

COMMITTEE MEMBERS:
Presidente - 1715271 - RENATA ANTONACI GAMA
Externo à Instituição - TACIANO DE MOURA BARBOSA
Externo à Instituição - VERUSKA CAVALCANTI BARROS