The use of a semiochemical bait to enhance exposure of Amblyomma variegatum (Acari: Ixodidae) to Metarhizium anisopliae (Ascomycota: Hypocreales)

Abstract

Experiments were conducted to explore the use of a semiochemical bait to enhance exposure of Amblyomma variegatum Fabricius (Acari: Ixodidae) to different formulations of the entomopathogenic fungus Metarhizium anisopliae (Metsch.) Sorok. (Ascomycota: Hypocreales). Initially, the relative efficacies of attraction-aggregation-attachment pheromone (AAAP), made up of o-nitrophenol, methyl salicylate and nonanoic acid in the ratio 2:1:8, 1-octen-3-ol and butyric acid, were evaluated in an olfactometer. Only AAAP and 1-octen-3-ol were found to elicit attractive responses to the tick. Simultaneous release of 1-octen-3-ol and AAAP together with CO 2 from a trap in semifield plots attracted up to 94.0 ± 6% of adult ticks from a distance of 6 m, and up to 24.0 ± 5.1% from 8 m. Formulations of M. anisopliae (dry powder, oil, and emulsifiable) applied within the trap baited with AAAP, 1-octen-3-ol and CO 2 resulted in high levels of contamination of the ticks attracted to the traps. However, 48 h after autoinoculation, 89.1 and 33.3% of conidia were lost in dry powder and oil formulations, respectively. Emulsifiable formulation showed least loss of propagules (17.1%). Samples of ticks attracted to the baited traps were transferred to plastic basins containing grass and maintained for 5 weeks. The experiment was conducted in rainy and dry seasons. Emulsifiable formulation gave the highest relative tick reduction in both seasons: 54.7 and 46.5% in rainy and dry seasons, respectively, followed by oil formulation (32.0 and 23.8%) and powder formulation (38.0 and 24.4%).

Compatibility between Calpurnia aurea leaf extract, attraction aggregation, and attachment pheromone and entomopathogenic fungus Metarhizium anisopliae on viability, growth, and virulence of the pathogen

“…On the other hand, phenolic compounds have been documented also to inhibit the growth of entomopathogenic fungi (Lopez-Llorca and Olivares-Bernabeu 1997). These results suggest that conidia of M. anisopliae cannot be mixed with AAAP but used separately (Nchu et al 2009.…”

“…Concentrations of 0.005, 0.01, and 0.02 mg/ml were used. Concentration of 0.02 mg/ml was previously shown to significantly attract R. appendiculatus (Nchu et al 2009). …”

“…The virulence of the isolated fungus was restored by passage through adult R. appendiculatus. Conidia were produced on long rice as substrate using Milner's bag process (Nchu et al 2009). …”

“…However, a new approach is being investigated, whereby ticks that are attracted to a semiochemicals, such as attraction-aggregation-attachment pheromone (AAAP), are infected with entomopathogenic fungi (Nchu et al 2009). Recently, Nchu et al (2010) reported reduction of Amblyomma variegatum Fabricius (Acari: Ixodidae) populations in the field by infecting them with conidia of M. anisopliae applied in semiochemical-baited traps.…”

Ecological considerations in producing and formulating fungal entomopathogens for use in insect biocontrol

“…Semiochemicals have also been used to lure various insects to a fungal entomopathogen infection site (Vega et al 2007). Insects targeted using this biocontrol approach include ticks [Amblyomma vaiegatum (Maranga et al 2006;Nchu et al 2009 (Smith et al 1999)], and the diamond-back moth [Plutella xylostella (Furlong et al 1995)]. …”