Helen L. Kutima

Attraction response of adult Rhipicephalus appendiculatus and Rhipicephalus pulchellus (Acari: Ixodidae) ticks to extracts from Calpurnia aurea (Fabaceae).

Experiments were carried out to investigate the response of two tick species Rhipicephalus pulchellus Gerstaker, 1873 and Rhipicephalus appendiculatus Neumann, 1901 to three different extracts (acetone, aqueous and oil) of the dried leaves of Calpurnia aurea (Aiton) Benth in both an inverted glass tube and a dual choice T-olfactometer. The oil extract at 50 and 100mg/ml attracted 46.7% and 65.9% of R. appendiculatus, respectively, in the inverted glass tube assay, which was comparable to 47.8% of the attraction-aggregation-attachment pheromone (AAAP) used as positive control. At a dose of 100mg/ml the oil extract attracted 52.4% of R. pulchellus in the T-olfactometer bioassay. The relative attraction of both tick species to plant extract was also tested in semi-field plot experiments using a trap baited with different concentrations of emulsifiable extract of C. aurea. A dose of 100mg/ml attracted 52.2% of R. pulchellus and 44.4% of R. appendiculatus from a distance of 1m while 14.4% of R. pulchellus and 12.2% of R. appendiculatus were attracted from 5m distance at the same dose. Addition of CO(2) to the plant extract-baited-trap at the dose of 100mg/ml increased the range of attraction of adult R. pulchellus (44.4% from 5m distance) and up to 33.3% of adult R. appendiculatus tick from a distance of 4m. The results of this study suggest that extracts from C. aurea can potentially be used as baits in a trap for the control of ticks in the field.

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

Metarhizium anisopliae sensu stricto (ss) (Metsch.) Sorok. isolate ICIPE 07 is being developed as biopesticide for the control of ticks. In addition, leaf extracts of Calpurnia aurea Benth, and the attraction aggregation and attachment pheromone (AAAP) are being used as ticks’ attractant. The three agents are being considered for use in combination in an autodissemination approach, whereby ticks that are attracted to semiochemicals are infected with the inoculum. Experiments were therefore conducted to evaluate in vitro the compatibility between C. aurea, AAAP, and the M. anisopliae on vegetative growth, conidial production, and spore viability. Calpurnia aurea leaf extract was compatible with the fungus at all the concentrations tested, whereas AAAP inhibited all the fungal growth parameters. The virulence of M. anisopliae formulated in emulsifiable extracts of C. aurea was also tested against different developmental stages of Rhipicephalus appendiculatus in laboratory bioassays. No significant differences in virulence were observed between M. anisopliae applied alone and M. anisopliae formulated in different concentrations of C. aurea leaf extracts. These results suggest that C. aurea leaf extracts is compatible with M. anisopliae and could be mixed together for “spot-spray” treatments as low-cost and environmental-friendly technology to control ticks in grazing field, while AAAP should be used separately.

Effect of larval age and supplemental feeding on morphometrics and oviposition in honey bee Apis mellifera scutellata queens

Although the effects of numerous factors (such as age of grafted larvae, supplemental feeding and mating) have been studied on the honey bees of Europe and America, they remain unknown for African bee races. To bridge this gap, a study was undertaken at the icipe Karura forest apiaries in Kenya to determine the effect of larval age and supplemental feeding on morphometrics and oviposition in the honey bee Apis mellifera scutellata queens. Queens were reared in 12 colonies with two feeding regimes, fed and not fed. Five larval age groups: 6, 12, 24, 36, and 48 h old, were grafted from each colony. We measured the fresh weight, spermatheca volume and the external parameters of the emerged queens and compared the oviposition rate by counting the number of eggs laid daily in naturally mated queens (NM) and artificially inseminated queens (AI). Our results show that age of grafted larvae and supplemental feeding significantly affect the morphometrics of the reared queens (p = 0.001), while oviposition rate is more or less the same in NM and AI. This work could eventually be used to select the best breed of honey bee subspecies in East Africa and improve queen rearing methods.