Renata da Silva Matos

Acaricidal activity of essential oil from Lippia sidoides on unengorged larvae and nymphs of Rhipicephalus sanguineus (Acari: Ixodidae) and Amblyomma cajennense (Acari: Ixodidae).

The aims of this work were to identify the compounds and to investigate the acaricidal activity of the essential oil of Lippia sidoides for unengorged larvae and nymphs of Rhipicephalus sanguineus and Amblyomma cajennense. The oil was analyzed by gas chromatography and gas chromatography/mass spectrometry. In total, 22 compounds comprising 98.5% of the total peak area were identified. The major constituent of the essential oil was thymol (69.9%). The acaricidal activity against larvae and nymphs was assessed using a modified larval packet test. In all experiments, oils were tested at concentrations of 2.35, 4.70, 9.40 14.10 and 18.80 mg/mL. The mortalities of larvae and nymphs of R. sanguineus were 20.6, 47.8, 73.6, 99.5 and 99.0% and 12.0, 50.0, 76.3, 96.0 and 96.1%, respectively. For larvae and nymphs of A. cajennense the rates of mortality were 41.9, 63.3, 77.8, 82.5 and 100.0% and 0.0, 32.8, 64.8, 71.1 and 94.0%, respectively. The LC 90 values of the L. sidoides oil were 11.56 and 12.97 mg/mL for larvae and nymphs of R. sanguineus and 15.70 and 18.52 mg/mL for larvae and nymphs of A. cajennense, respectively. The essential oil from L. sidoides has acaricidal activity on unengorged larvae and nymphs of R. sanguineus and A. cajennense.

Entomopathogenic nematodes in insect cadaver formulations for the control of Rhipicephalus microplus (Acari: Ixodidae)

This study evaluated the efficacy of four entomopathogenic nematode (EPN) strains in insect cadaver formulations against Rhipicephalus microplus and compared the efficacy of the most virulent EPNs applied in cadavers of Galleria mellonella and Tenebrio molitor. In the first experiment, infected G. mellonela larvae were used as the source of EPNs. Engorged females of R. microplus were placed in pots filled with soil and different numbers of G. mellonella larvae infected with one of four species of nematodes. All treatments with EPNs of the genus Heterorhabditis caused significant reduction (p<0.05) in the egg mass weight and hatching percentage of larvae. The EPNs of the genus Steinernema, except for the group exposed to Steinernema carpocapsae ALL, whose source nematodes included six larvae of G. mellonella, caused a significant reduction (p<0.05) in the egg mass weight produced per female. Steinernema feltiae SN applied with two, four, and six cadavers and S. carpocapsae ALL with two cadavers caused a reduction in hatching percentage of larvae of R. microplus (p<0.05). The percentage of control was above 95% in all groups treated with Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 and in the treatment with four larvae infected with S. feltiae SN. The second experiment followed the same methodology, using G. mellonella and T. molitor larvae infected by the two most virulent EPNs. H. bacteriophora HP88 and H. indica LPP1 in different formulations caused reduction in the egg mass weight and hatching percentage of larvae. The percentage of control were 82.4 and 84.9% for H. bacteriophora HP88 and H. indica LPP1, respectively, formulated in T. molitor, and reaching 99.9% in groups formulated with G. mellonella. The EPNs tested in insect cadaver formulation showed pathogenicity to engorged females of R. microplus and EPNs of the genus Heterorhabditis formulated in G. mellonella larvae were more effective.

Compatibilidade de Heterorhabditis amazonensis (Rhabditida: Heterorhabditidae) isolado RSC-5 com diferentes carrapaticidas utilizados no controle de Rhipicephalus microplus(Acari: Ixodidae)

The aim of this study was to assess the viability of Heterorhabditisamazonensis strain RSC-5 after exposure to different acaricides used for Rhipicephalusmicropluscontrol. Six treatment groups were formed, one for each product. Each group was composed of 75,000 nematodes in a 20 mL solution of different acaricides, at commercial concentration. The control group was formed by the same number of nematodes in 20 mL of distilled water. All the groups were kept in a climate-controlled chamber at 25°C. The percentage of survival and infectivity in Galleria mellonella caterpillars were determined 24 and 72 hours after the beginning of the experiment. The mortality of the caterpillars in the infectivity test was assessed 72 and 120 hours. After 24 hours of exposure, only the active ingredient deltamethrin did not significantly reduce the survival percentage of H. amazonensis RSC-5 (p > 0.05). The same was observed after 72 hours of exposure to the combination of chlorpyriphos + cypermethrin + piperonyl butoxide + citronellal. There was no survival of infective juveniles in the groups exposed to the combination of chlorphenvinphos + dichlorvos. The exposure to chlorphenvinphos for 72 hours resulted in 50% of mortality. The potential to infect G. mellonella caterpillars was only reduced in the group treated with the active ingredient chlorphenvinphos. Chlorphenvinphos and the combination of chlorphenvinphos + dichlorvos were not compatible with H. amazonensisRSC-5, causing a reduction in the survival and infectivity of juveniles of this nematode, while the other products were compatible, causing no reduction in the infectivity of this isolate.