III WOCMAP Congress on Medicinal and Aromatic Plants - Volume 5: Quality, Efficacy, Safety, Processing and Trade in Medicinal and Aromatic Plants, 2005
ABSTRACT The fumigant and repellent effects of Ocimum gratissimum L. oil and its constituents, β-... more ABSTRACT The fumigant and repellent effects of Ocimum gratissimum L. oil and its constituents, β-(Z)-ocimene and eugenol, were evaluated against adults of Sitophilus oryzae (L.), Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.) and Callosobruchus chinensis (L.). The fumigant toxicities of the oil and two of its constituents were assessed at four rates (0, 1, 5 and10 μL/L air) in space fumigation, whereas repellence of the oil and eugenol in acetone was evaluated in choice bioassays at five rates (0, 1.0, 2.0, 3.0 and 4.0 μL oil/2 g grain). Results showed that fumigant toxicity and repellence of the oil and its constituents were significantly (P<0.0001) influenced by concentration and time after treatment. At 1 μL/L air, the oil caused 98%, 99% and 100% mortality of R. dominica, O. surinamensis and C. chinensis, respectively, 24 h after treatment, whereas eugenol achieved 79%, 61% and 100% kill of the same insects. β-(Z)-ocimene produced a weaker toxicity with 8%, 11% and 59% mortality of R. dominica, O. surinamensis and C. chinensis, respectively. Except for T. castaneum which was more tolerant, LC50 values for tested insects ranged from 0.20 to 14, 0.01 to 17 and 0.80 to 23 μL/L air 24 h after treatment for O. gratissimum oil, eugenol and β-(Z)-ocimene, respectively. All test insects had percentage repellence (PR) values which ranged from 37.5% to 100% and 45% to 100% for the oil and eugenol, respectively. However, C. chinensis showed a dose-dependent decrease in PR values in the eugenol bioassay with a corresponding dose-dependent mortality on treated grains. Ocimum gratissimum oil and its constituents are potential alternatives to synthetic fumigants in the treatment of durable agricultural products. Successful adoption of plant oils in the protection of food commodities promises an eco-friendly option compatible with international biosafety regulations.
... Arop Leek Deng * , Baldwyn Torto * , Corresponding Author Contact Information , Ahmed Hassana... more ... Arop Leek Deng * , Baldwyn Torto * , Corresponding Author Contact Information , Ahmed Hassanali * and EE Ali ... RESULTS Pheromone titres Pheromone emissions of adults obtained from gregari ous locust shifted at nymphal or fledgling stages to soli tary conditions and those ...
Females of Anopheles gambiae Giles normally oviposit in a large number of fresh, small, sunlit, a... more Females of Anopheles gambiae Giles normally oviposit in a large number of fresh, small, sunlit, and spatially spread temporary pools. Such pools are associated with lower levels of predation compared to large, longer-lasting habitats. We compared oviposition levels on preferred (water collected from natural anopheline larval habitats) and non-preferred (distilled water) aqueous substrates by gravid females that contained different densities of conspecific eggs or early and late instar larvae. The presence of conspecific larvae, but not eggs, had a positive or negative effect on the ovipositional responses of gravid An. gambiae females, depending on the quality (preferred or non-preferred by the mosquito) of the oviposition water and the density of larvae. Presence of larvae, at all densities, in distilled water deterred oviposition. However, in natural anopheline pool water, a low density of larvae increased oviposition, whereas a higher density inhibited oviposition. Our results suggest that two signals produced by this mosquito may be involved in regulating oviposition: a volatile pheromone emitted by conspecific larvae, which augments the effect of a volatile signal emitted by preferred habitats, and a non-olfactory cue associated with high densities of larvae that deters oviposition.
International Journal of Tropical Insect Science, 2004
Abstract Laboratory studies were carried out to investigate the role of larval habitat-derived mi... more Abstract Laboratory studies were carried out to investigate the role of larval habitat-derived microorganisms in the production of semiochemicals for oviposition site selection by Anopheles gambiae Giles sensu stricto mosquitoes. Dual-choice bioassays with gravid ...
BACKGROUND: Anopheles gambiae Giles is the most important vector of human malaria in sub-Saharan ... more BACKGROUND: Anopheles gambiae Giles is the most important vector of human malaria in sub-Saharan Africa. Knowledge of the factors that influence its daily oviposition pattern is crucial if field interventions targeting gravid females are to be successful. This laboratory study investigated the effect of oviposition substrate and time of blood feeding on daily oviposition patterns of An. gambiae mosquitoes. METHODS: Greenhouse-reared gravid and hypergravid (delayed oviposition onset) An. gambiae sensu stricto and wild-caught An. gambiae sensu lato were exposed to three types of substrates in choice and no-choice cage bioassays: water from a predominantly anopheline colonised ground pool (anopheline habitat water), swamp water mainly colonised by culicine larvae (culicine habitat water) and distilled water. The daily oviposition pattern and the number of eggs oviposited on each substrate during the entire egg-laying period were determined. The results were subjected to analysis of var...
III WOCMAP Congress on Medicinal and Aromatic Plants - Volume 5: Quality, Efficacy, Safety, Processing and Trade in Medicinal and Aromatic Plants, 2005
ABSTRACT The fumigant and repellent effects of Ocimum gratissimum L. oil and its constituents, β-... more ABSTRACT The fumigant and repellent effects of Ocimum gratissimum L. oil and its constituents, β-(Z)-ocimene and eugenol, were evaluated against adults of Sitophilus oryzae (L.), Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.) and Callosobruchus chinensis (L.). The fumigant toxicities of the oil and two of its constituents were assessed at four rates (0, 1, 5 and10 μL/L air) in space fumigation, whereas repellence of the oil and eugenol in acetone was evaluated in choice bioassays at five rates (0, 1.0, 2.0, 3.0 and 4.0 μL oil/2 g grain). Results showed that fumigant toxicity and repellence of the oil and its constituents were significantly (P<0.0001) influenced by concentration and time after treatment. At 1 μL/L air, the oil caused 98%, 99% and 100% mortality of R. dominica, O. surinamensis and C. chinensis, respectively, 24 h after treatment, whereas eugenol achieved 79%, 61% and 100% kill of the same insects. β-(Z)-ocimene produced a weaker toxicity with 8%, 11% and 59% mortality of R. dominica, O. surinamensis and C. chinensis, respectively. Except for T. castaneum which was more tolerant, LC50 values for tested insects ranged from 0.20 to 14, 0.01 to 17 and 0.80 to 23 μL/L air 24 h after treatment for O. gratissimum oil, eugenol and β-(Z)-ocimene, respectively. All test insects had percentage repellence (PR) values which ranged from 37.5% to 100% and 45% to 100% for the oil and eugenol, respectively. However, C. chinensis showed a dose-dependent decrease in PR values in the eugenol bioassay with a corresponding dose-dependent mortality on treated grains. Ocimum gratissimum oil and its constituents are potential alternatives to synthetic fumigants in the treatment of durable agricultural products. Successful adoption of plant oils in the protection of food commodities promises an eco-friendly option compatible with international biosafety regulations.
... Arop Leek Deng * , Baldwyn Torto * , Corresponding Author Contact Information , Ahmed Hassana... more ... Arop Leek Deng * , Baldwyn Torto * , Corresponding Author Contact Information , Ahmed Hassanali * and EE Ali ... RESULTS Pheromone titres Pheromone emissions of adults obtained from gregari ous locust shifted at nymphal or fledgling stages to soli tary conditions and those ...
Females of Anopheles gambiae Giles normally oviposit in a large number of fresh, small, sunlit, a... more Females of Anopheles gambiae Giles normally oviposit in a large number of fresh, small, sunlit, and spatially spread temporary pools. Such pools are associated with lower levels of predation compared to large, longer-lasting habitats. We compared oviposition levels on preferred (water collected from natural anopheline larval habitats) and non-preferred (distilled water) aqueous substrates by gravid females that contained different densities of conspecific eggs or early and late instar larvae. The presence of conspecific larvae, but not eggs, had a positive or negative effect on the ovipositional responses of gravid An. gambiae females, depending on the quality (preferred or non-preferred by the mosquito) of the oviposition water and the density of larvae. Presence of larvae, at all densities, in distilled water deterred oviposition. However, in natural anopheline pool water, a low density of larvae increased oviposition, whereas a higher density inhibited oviposition. Our results suggest that two signals produced by this mosquito may be involved in regulating oviposition: a volatile pheromone emitted by conspecific larvae, which augments the effect of a volatile signal emitted by preferred habitats, and a non-olfactory cue associated with high densities of larvae that deters oviposition.
International Journal of Tropical Insect Science, 2004
Abstract Laboratory studies were carried out to investigate the role of larval habitat-derived mi... more Abstract Laboratory studies were carried out to investigate the role of larval habitat-derived microorganisms in the production of semiochemicals for oviposition site selection by Anopheles gambiae Giles sensu stricto mosquitoes. Dual-choice bioassays with gravid ...
BACKGROUND: Anopheles gambiae Giles is the most important vector of human malaria in sub-Saharan ... more BACKGROUND: Anopheles gambiae Giles is the most important vector of human malaria in sub-Saharan Africa. Knowledge of the factors that influence its daily oviposition pattern is crucial if field interventions targeting gravid females are to be successful. This laboratory study investigated the effect of oviposition substrate and time of blood feeding on daily oviposition patterns of An. gambiae mosquitoes. METHODS: Greenhouse-reared gravid and hypergravid (delayed oviposition onset) An. gambiae sensu stricto and wild-caught An. gambiae sensu lato were exposed to three types of substrates in choice and no-choice cage bioassays: water from a predominantly anopheline colonised ground pool (anopheline habitat water), swamp water mainly colonised by culicine larvae (culicine habitat water) and distilled water. The daily oviposition pattern and the number of eggs oviposited on each substrate during the entire egg-laying period were determined. The results were subjected to analysis of var...
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