School of Pure and Applied Sciences
Permanent URI for this communityhttp://localhost:4000/handle/20.500.12092/1952
Browse
7 results
Search Results
Item Interaction between Phaedrotomascabriventris Nixon and Opiusdissitus Muesebeck (Hymenoptera: Braconidae) : endoparasitoids of Liriomyza leafminer(Sabinet African Journals, 2015-03-01) Foba, C.N.; Akutse, K.S.; Fiaboe, K.K.M.; Lagat, Z.O.; Gitonga, L.M.The exotic parasitoid, Phaedrotoma scabriventris Nixon, was imported from Peru for the biological control of invasive Liriomyza species in vegetable and ornamental crops in Kenya where Opius dissitus Muesebeck is the most abundant indigenous Liriomyza parasitoid. Both species are solitary larva-pupal endoparasioids attacking the same larval stage. In order to assess whether these two species compete or co-exist, an interaction study involving sole, sequential and simultaneous releases of the two species on polyphagous Liriomyza huidobrensis (Blanchard) was conducted in the laboratory at the International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya. Simultaneous releases of 50 individuals each of the two parasitoids resulted in significantly higher total parasitism rate (61.96 ± 4.60) than in the single release of P. scabriventris (34.94 ± 8.50). Simultaneous release of 25 individuals of each species resulted in a parasitism rate (44.52 ± 2.75) similar to that obtained for single releases of 50 individuals of O. dissitus (42.57 ± 3.35) and P. scabriventris (34.94 ± 8.50). No significant effect was observed in total parasitism between sequential and single releases of 50 individuals of each species. The specific parasitism rate of each parasitoid species in the simultaneous release of 50 individuals of each species was not significantly different from when each species was released alone. The first introduced parasitoid in sequential releases achieved the same parasitism rate as when released alone. However, the second released species gave a significantly lower parasitism rate than when released alone and compared to the first released species. The F1 progeny sex ratio was balanced for P. scabriventris but male-biased in O. dissitus. The sex ratios of both parasitoid species were not significantly affected, neither in simultaneous nor sequential releases, except in one of the sequential release where P. scabriventris was released second, with its sex ratio significantly female-biased. Non-reproductive host mortality was not important for both parasitoids when used alone and in combined releases compared to the natural mortality observed in the control. These findings suggest that P. scabriventris has no detrimental effect on O. dissitus and its release into Kenya's agricultural ecosystems will enhance the management of Liriomyza leafminer.Item Evidence for Potential of Managing Some African Fruit Fly Species (Diptera: Tephritidae) Using the Mango Fruit Fly Host-Marking Pheromone(JOURNAL OF ECONOMIC ENTOMOLOGY, 2012-12) Kachigamba, D.L.; Ekesi, S.; Ndung'u, M.; Gitonga, L.M.; Teal, P.E.A.; Torto, B.We investigated conspecific and heterospecific oviposition host discrimination among four economically important fruit fly pests of mango in Africa (Ceratitis capitata, Wiedemann; C. fasciventris, Bezzi; C. rosa, Karsch, and C. cosyra, Walker) with regard to host-marking behavior and fecal matter aqueous solutions. The objective of the study was to get insight into the potential of managing these pests using the host-marking technique. Observations were done on mango slices marked by the flies and treated with aqueous solutions of fecal matter of the flies, respectively. In both host-marking and fecal matter experiments, C. cosyra, which is the most destructive species of the four on mango, was exceptional. It only discriminated against hosts treated with its fecal matter but with lower sensitivity while C. capitata and C.fasciventris discriminated against hosts marked by it or treated with its fecal matter and with higher sensitivity. Our results provide evidence for potential of managing some of the major fruit fly species infesting mango in Africa using the host-marking pheromone of the mango fruit fly, C. cosyra.Item Relationship between virulence and repellency of entomopathogenic isolates of Metarhizium anisopliae and Beauveria bassiana to the termite Macrotermes michaelseni(Journal of Insect Physiology, 2009) Mburu, D.M.; Ochola, L.; Maniania, N.K; Njagi, P.G.N.; Gitonga, L.M.; Ndung'u, M.W.; Wanjoya, A.K.; Hassanali, A.Termites encounter a diverse array of potentially useful and harmful fungi in their subterranean habitats. These vary from symbiotic to harmful species with varying levels of virulence. How these hemiedaphic insects survive in habitats with infective fungi is not well understood. Possible mediation of olfactory signals in avoiding contact with entomopathogenic fungi has been explored by a number of workers. In the present study, we initially found that Macrotermes michaelseni detected a virulent isolate of Metarhizium anisopliae from some distance and avoided direct physical contact. We hypothesized that there may be a relationship between virulence and repellency of different isolates of M. anisopliae and Beauveria bassiana to the termite. We compared these for selected isolates of the two fungi. Positive correlations between the two parameters for both sets of isolates of the fungi were obtained. The results show an interesting co-evolutionary phenomenon in which the termite’s response to either M. anisopliae or B. bassiana is directly related to potential harm these fungi can inflict on the insect and that the virulent strains are more likely to be recognized from some distance and avoided.Item Selection of promising fungal biological control agent of the western flower thrips Frankliniella occidentalis (Pergande)(Letters of Applied Microbiology, 2012-02) Niassy, S.; Maniania, N.K; Subramanian, S.; Gitonga, L.M.; Mburu, D.M.; Masiga, D.; Ekesi, S.Aims: Larval stages of Frankliniella occidentalis are known to be refractory to fungal infection compared with the adult stage. The objective of this study was to identify promising fungal isolate(s) for the control of larval stages of F. occidentalis. Methods and Results: Ten isolates of Metarhizium anisopliae and eight of Beauveria bassiana were screened for virulence against second-instar larvae of F. occidentalis. Conidial production and genetic polymorphism were also investigated. Metarhizium anisopliae isolates ICIPE 7, ICIPE 20, ICIPE 69 and ICIPE 665 had the shortest LT50 values of 8Æ0–8Æ9 days. ICIPE 69, ICIPE 7 and ICIPE 20 had the lowest LC50 values of 1Æ1 · 107 , 2Æ0 · 107 and 3Æ0 · 107 conidia ml)1 , respectively. Metarhizium anisopliae isolate ICIPE 69 produced significantly more conidia than M. anisopliae isolates ICIPE 7 and ICIPE 20. Internally transcribed spacers sequences alignment showed differences in nucleotides composition, which can partly explain differences in virulence. Conclusion: These results coupled with the previous ones on virulence and field efficacy against other species of thrips make M. anisopliae isolate ICIPE 69 a good candidate. Significance and Impact of the Study: Metarhizium anisopliae isolate ICIPE 69 can be suggested for development as fungus-based biopesticide for thrips management.Item Compatibility of Metarhizium anisopliae isolate ICIPE 69 with agrochemicals used in French bean production(Journal of Pest Management, 2012-04) Niassy, S.; Maniania, N.K; Subramanian, S.; Gitonga, L.M.; Maranga, R.; Obonyo, A.B.; Ekesi, S.The compatibility of the Metarhizium anisopliae (Metschnikoff) Sorokin isolate ICIPE 69, which is being developed as a biopesticide for the control of Frankliniella occidentalis Pergande, was assessed under laboratory conditions with 12 agrochemicals including 5 insecticides (thiamethoxam, L-cyhalothrin, imidacloprid, chlorpyrifos, diazinon), 1 botanical insecticide (azadirachtin), 2 acaricides (abamectin, spiromesifen), and 3 fungicides (carbendazim, copper hydroxide, probineb) used in French bean production. The insecticides abamectin and imidacloprid were highly compatible with M. anisopliae; thiamethoxam was compatible, whereas azadirachtin and L-cyahalothrin were toxic to the fungus, adversely affecting vegetative growth and sporulation. The acaricide spiromesifen was moderately toxic, while the fungicides carbendazim, probineb, and copper-hydroxide were very toxic to the fungus. The combination of the M. anisopliae isolate ICIPE 69 with imidacloprid or thiamethoxam did not result in any synergistic or antagonistic effects to larvae of F. occidentalis. However, the combination of lower concentrations of the fungus with thiamethoxam resulted in a shorter lethal time (LT50) compared with individual treatments. Our results suggest that application of the fungus with agrochemicals has to be assessed carefully prior to any field intervention.Item Interaction between Phaedrotoma scabriventris Nixon and Opius dissitus Muesebeck (Hymenoptera: Braconidae): endoparasitoids of Liriomyza leafminer(African Entomology, 2015) Foba, C.N; Langat, Z.O.; Gitonga, L.M.; Akutse, K.S.; Fiaboe, K.K.M.The exotic parasitoid, Phaedrotoma scabriventris Nixon, was imported from Peru for the biological control of invasive Liriomyza species in vegetable and ornamental crops in Kenya where Opius dissitus Muesebeck is the most abundant indigenous Liriomyza parasitoid. Both species are solitary larva-pupal endoparasioids attacking the same larval stage. In order to assess whether these two species compete or co-exist, an interaction study involving sole, sequential and simultaneous releases of the two species on polyphagous Liriomyza huidobrensis (Blanchard) was conducted in the laboratory at the International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya. Simultaneous releases of 50 individuals each of the two parasitoids resulted in significantly higher total parasitism rate (61.96 ± 4.60) than in the single release of P. scabriventris (34.94 ± 8.50). Simultaneous release of 25 individuals of each species resulted in a parasitism rate (44.52 ± 2.75) similar to that obtained for single releases of 50 individuals of O. dissitus (42.57 ± 3.35) and P. scabriventris (34.94 ± 8.50). No significant effect was observed in total parasitism between sequential and single releases of 50 individuals of each species. The specific parasitism rate of each parasitoid species in the simultaneous release of 50 individuals of each species was not significantly different from when each species was released alone. The first introduced parasitoid in sequential releases achieved the same parasitism rate as when released alone. However, the second released species gave a significantly lower parasitism rate than when released alone and compared to the first released species. The F1 progeny sex ratio was balanced for P. scabriventris but male-biased in O. dissitus. The sex ratios of both parasitoid species were not significantly affected, neither in simultaneous nor sequential releases, except in one of the sequential release where P. scabriventris was released second, with its sex ratio significantly female-biased. Non-reproductive host mortality was not important for both parasitoids when used alone and in combined releases compared to the natural mortality observed in the control. These findings suggest that P. scabriventris has no detrimental effect on O. dissitus and its release into Kenya’s agricultural ecosystems will enhance the management of Liriomyza leafminer.Item Species Composition, Distribution, and Seasonal Abundance of Liriomyza Leafminers (Diptera: Agromyzidae) Under Different Vegetable Production Systems and Agroecological Zones in Kenya(Environmental Entomology, 2015-02-03) Foba, C.N; Salifu, D.; Langat, Z.O.; Gitonga, L.M.; Akutse, K.S.; Fiaboe, K.K.M.A longitudinal study to identify the species of Liriomyza leafminer, their distribution, relative abundance, and seasonal variation, including their host range, was conducted in vegetable fields at three altitudes in Kenya from November 2011 to November 2012. Three main species were identified: Liriomyza huidobrensis (Blanchard), Liriomyza sativae Blanchard, and Liriomyza trifolii (Burgess), of which L. huidobrensis was the most abundant across all altitudes irrespective of the cropping season and accounting for over 90% of the total Liriomyza specimens collected. Liriomyza species were collected from all infested incubated leaves of 20 crops surveyed belonging to seven families: Fabaceae, Solanaceae, Cucurbitaceae, Malvaceae, Brassicaceae, Amaranthaceae, and Amaryllidaceae. However, more than 87.5% of the Liriomyza species were obtained from only four of these crops: Pisum sativum L., Phaseolus vulgaris L., Solanum lycopersicum L., and Solanum tuberosum, thereby demonstrating that Fabaceae and Solonaceae crops are the most important hosts with regard to Liriomyza species richness and relative abundance. L. huidobrensis had the widest host range (20 crops), followed by L. sativae (18 crops) and L. trifolii (12 crops). Although L. trifolii has been considered the dominant Liriomyza leafminer in Kenya, this study suggests that this may not be the case anymore, as L. huidobrensis dominates at all altitudes.