Browsing by Author "Cobblah, M.A."

Now showing 1 - 13 of 13

Cross mating studies among five fruit fly parasitoid populations: Potential biological control implications for tephritid pests
(BioControl, 2008-10) Billah, M.K.; Kimani-Njogu, S.W.; Wharton, R.A.; Overholt, W.A.; Wilson, D.D.; Cobblah, M.A.
The reproductive compatibility between four different species/populations of the tephritid parasitoid Psyttalia (Walker) species from Kenya and individuals of the morphologically identical Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) from a laboratory culture in Italy used in augmentative biological control of olive fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae) was assessed through cross mating tests using single-pair and group mating methods. Reciprocal crosses among the species resulted in the production of viable offsprings up to the second generation. In spite of the successful production of viable offspring in the laboratory, Psyttalia species are known to have specific host fruit and/or host fly preferences and populations/species may be isolated in one way or the other. However, it is not known whether these populations/species interbreed in the field. We discuss the ability of these parasitoids to interbreed and the potential effects of that on their use as biological control agents, especially in environments where other closely related species are present or in situations where multiple parasitoid introductions are intended. © 2007 International Organization for Biological Control (IOBC).
Cross mating studies of Psyttalia species (Hymenoptera: Braconidae): Potential implications for biological control of tephritid pests
(BioControl 53 (5): 709-724, 2008) Billah, M.K.; Kimani-Njogu, S.W.; Overholt, W.A.; Wharton, R. A.; Wilson, D.D.; Cobblah, M.A.
The reproductive compatibility between four different species/populations of the tephritid parasitoid Psyttalia (Walker) species from Kenya and individuals of the morphologically identical Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) from a laboratory culture in Italy used in augmentative biological control of olive fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae) was assessed through cross mating tests using single-pair and group mating methods. Reciprocal crosses among the species resulted in the production of viable offsprings up to the second generation. In spite of the successful production of viable offspring in the laboratory, Psyttalia species are known to have specific host fruit and/or host fly preferences and populations/species may be isolated in one way or the other. However, it is not known whether these populations/species interbreed in the field. We discuss the ability of these parasitoids to interbreed and the potential effects of that on their use as biological control agents, especially in environments where other closely related species are present or in situations where multiple parasitoid introductions are intended.
Cytotaxonomy of Simulium soderense sp. nov. and a redescription of the ‘Kulfo’form (Dunbar, 1969) of Simulium damnosum s.l. (Diptera: Simuliidae) as Simulium kulfoense sp. nov. in Ethiopia
(International Journal of Tropical Insect Science, 2008) Hadis, M.; Wilson, M.D.; Cobblah, M.A.; Boakye, D.A.
The exact taxonomic identity of members of the Simulium damnosum Theobald complex in Ethiopia was not known until recently. A cytotaxonomic analysis of larval chromosomes from the Kulfo River area in southern Ethiopia, from where the ‘Kulfo’ form was reported, and from the Awash River at Sodere in central Ethiopia has revealed the existence of two newly recognized species, namely Simulium kulfoense and Simulium soderense. Although three fixed and 11 floating inversions in the chromosomes of the ‘Kulfo’ form were described in an idiogram, in the present study four fixed and 17 floating inversions were observed, out of which only seven floating inversions were the same as Dunbar’s, indicating that the remaining 10 inversions were either missed or misinterpreted. Though both species share many inversions, S. kulfoense sp. nov. has a diagnostic inversion on chromosome II, IIL-E6, with no sex-linked chromosomal arrangement, while S. soderense sp. nov. has a sex-linked inversion, IIS-3, which warrants it as a distinct species. Both of these new species also share many inversions with the recently described new species from southwestern Ethiopia, Simulium kaffaense, including the fixed inversions IIL-E1 and E3. Since both the study sites are known to be free of onchocerciasis, and the flies are not anthropophilic, both the species are not presumed to be vectors of human onchocerciasis. The presence of IS-1 and a complex inversion possibly involving IL-3 strongly indicates that the two species belong to the ‘Nile’ phylogenetic group of S. damnosum
Development of a Bait System for the Pharaoh’s Ant, Monomorium Pharaonis L. (Hymenoptera: Formicidae)
(2011) Osae, M.Y.; Cobblah, M.A.; Djankpa, F.T.; Lodoh, E.; Botwe, P.K.
Differential effects of weather, plant phenology and predators on the seasonal variation of aphids on cabbage
(Journal of Applied Entomology, 2023) Forchibe, E.E.; Fening, K.O.; Narh-Madey, B.; Afreh-Nuamah, K.; Cobblah, M.A.; Wamonje, F.O.; Carr, J.P.
The aphids Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) pose serious threats to the production of cruciferous crops in the tropics. Understanding their population dynamics is important for developing integrated pest management programmes to minimize their damage to crops. This study investigated the effects of climatic factors, natural enemies and plant age on the population dynamics of these pests. The population density of aphids and their natural enemies in 20 cabbage plants, and weather conditions were monitored for five cropping seasons from 2019 to 2021 in two agroecological zones of Ghana (Coastal Savannah and Deciduous Forest zones). The highest population density of L. e pseudobrassicae was recorded in January (dry season) in both agroecological zones, while the highest population density for M. persicae occurred in September (minor rainy season) and August (dry spell) in the Coastal Savannah and Deciduous Forest zones, respectively. The highest aphid densities were noted to occur during periods with low relative humidity and low rain fall. The population density of L. e. pseudobrassicae was significantly negatively related to plant age, air temperature and relative humidity, and positively related to syrphids (Paragus borbonicus) and spiders in the Coastal Savannah zone, while in the Deciduous Forest zone, it was significantly positively related to coccinellids. On the other hand, M. persicae population density was significantly positively related to syrphids and coccinellids in the Deciduous Forest zone. Rainfall negatively affected syrphids in the Coastal Savannah zone, while air temperature positively affected syrphids and negatively affected spiders in the Deciduous Forest zone. Coccinellids had a significant positive relationship with relative humidity in the Deciduous Forest zone. This study provides important insights into the key factors that regulate aphid population densities on cabbage and will support development of timely interventions to manage these pests.
The effect of host larvae on three Psyttalia species (Hymenoptera: Braconidae), parasitoids of fruit-infesting flies (Diptera: Tephritidae)
(International Journal of Tropical Insect Science, 2005-09) Billah, M.K.; Kimani-Njogu, S.; Overholt, W.A.; Wharton, R.A.; Wilson, D.D.; Cobblah, M.A.
Three species of fruit fly parasitoids, Psyttalia concolor (Szépligeti), Psyttalia cosyrae (Wilkinson) and Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae) were reared on different host larvae to determine the effects of host species, size and colour on parasitoid development. Ovipositor, ovipositor sheath and hind tibia lengths were found to be different for progenies from preferred and non-preferred host larvae. Ratios of ovipositor-tibia and ovipositor sheath-tibia showed no difference when P. concolor was reared on a bigger host (Ceratitis cosyra (Walker) (Diptera: Tephritidae), whereas rearing P. cosyrae on a smaller host (C. capitata (Wiedemann) showed significant differences. Comparison of the linear measurements, ratios and number of flagellomeres of parasitoids reared on preferred hosts, separated the species into their natural groupings. When reared on a different-coloured host, P. lounsburyi lost its dark markings but other characters remained unchanged. Morphometric analysis also indicated differences between parasitoids reared on preferred host larvae and those reared on non-preferred host larvae. Rearing parasitoids on larvae other than their preferred hosts resulted in colour and size changes, and thus, these characters alone were not reliable for the identification of parasitoids. This is especially important in post-release sampling surveys to ascertain establishment of the parasitoids in new environments where they may adapt to new host species. © ICIPE 2005.
Gamma radiation sterilization of Bactrocera invadens (Diptera: Tephritidae) from southern Ghana
(2012) Ogaugwu, C.; Wilson, D.; Cobblah, M.A.; Annoh, C.
The Incidence of Major Lepidopteran Pests on Cabbage and their Associated Parasitoids in Ghana
(University of Ghana, 2009-08) Cobblah, M.A.; Wilson , D.D.; Afreh-Nuamah, K.; University of Ghana, College of Basic and Applied Sciences, School of Biological Sciences, Department of Animal Biology and Conservation Science
The study was carried out at the Weija Irrigation Company site at Tubaman, Weija, the Laboratories of the Department of Zoology (now Department of Animal Biology and Conservation Science, DABCS), University of Ghana, Legon and some selected districts of Ghana. It was designed to; identify and establish the major Lepidopteran pests on cabbage, Brassica oleracea (L.) var. capitata and their parasitoids, determine the effect of the commonly used insecticides on parasitism and the biology of the major parasitoid, describe and illustrate the pests and their parasitoids to aid in identification. The rationale for the study was to provide information for implementation of effective integrated pest management in cabbage production in Ghana. Field studies were carried out at the Weija site for three years. The design of the experiments was a randomized complete block design. Indirect and direct methods were used to investigate the effect of four insecticides namely, a synthetic pyrethroid (Karate), a Bacillus thuringiensis formulation, neem seed water extract and a commercial neem formulation, (Neemazal) on the major parasitoid. The illustrations were made using the scanning electron microscope, photomicroscope, a digital camera and Camera Lucida drawings. The pests recorded were Plulella xylostella L., Trichoplusia rti (Hvibner). Hellula undalis (F), Helicoverpa armigera (HUbner) and Spodoptera littoralis (Boisduval). Plulella xylostella was the most abundant pest recorded during the study period. There was no significant difference between its larval density per plant in the major rainy season (0.15 ± 0.04, p > 0.05) compared with the minor rainy season (0.20 ± 0.07, p > 0.05): and also between the minor rainy season and the dry season (0.29 ± 0.5, p > 0.05). On the other hand, T. ni was only abundant during the major rainy season. There was a significant difference between larval density per plant during this season (0.60 ± 0.11, p < 0.05) compared with the other seasons. With regard to S. litloralis, there was a significant difference between its larval density per plant in the minor rainy season (0.39 ± 0.10, p < 0.05) compared with the other seasons. The other pests occurred in insignificant numbers. Out of the 15 species of parasitoids recorded from the pests, 7 were identified to the species level, 6 to the generic level and 2 to species groups. Seven of the species: Charops sp.. Brachymeria sp.. Hockeria sp., Elasmus sp., Notanisomorphella sp., Tetrastichus atriclavus S.L., Pediobius sp. and Trichomalopsis sp. were recorded for the first time in Ghana and may also be new species. The major parasitoid was Cotesia plutellae (Kurdjumov) which accounted for 92% and 60.9% of the parasitoids recorded from P. xylosiella and T. ni, respectively. The second important parasitoid was Euplectrus laphygmae (Ferriere) and it was specific to T. ni and S. litloralis. The facultative hyperparasitoids of P. xylostella were Oomyzus sokolowskii (Kurdjumov), Elasmus sp.? Aphanogmus reticulatus (Fouts) and Trichomalopsis sp. via C. plutellae. Blepharella vasta (Karsh), Peribaea orbata (Wiedemann), Notanisomorphella sp and Chelonus cunirnaculaliis (Cameron) were specific to the larvae of S. littoralis. No parasitoids were recorded from H. armigera. No egg parasitoid was observed. There was seasonal variation in parasitism of P. xylostella by C. plutellae. The rate of parasitism (6 8 .6 ± 12.9%, p < 0.05) was significantly highest in the major rainy season and significantly least (9.9 ± 7.1 %, p < 0.05) in the minor rainy season. The rate of parasitism of P. xylostella by C. plutellae did not differ among the unsprayed and insecticide treated plots. However, adult C. plutellae emerging from pests collected from 'Karate' treated plots sometimes died in the process of eclosion or were short - lived. Neem seed water extract applied at 50 g/l also adversely affected the ability of the parasitoid larva to spin its cocoon for pupation. Of the three insecticides. ‘Karate’ was the most toxic causing 100% mortality to the adult Cotesia pluiellae within ten seconds of direct exposure. Neemazal and Bt. applied at 1.0% and 1 .Og/liter of water respectively, were the least toxic to the adult. It is concluded that P. xylostella is the major pest of cabbage in Ghana, while T. ni and S. littoralis are abundant only during the major and minor rainy seasons respectively. Cotesia pluiellae and E. laphygmae are the major parasitoids and they should be considered in the development of any integrated pest management on cabbage. Karate has a harmful effect on C. pluiellae adults. Even though, Neem seed applied at 50g/I adversely affected the development of C. pluiellae, lower doses, or Bacillus thuringiensis formulations could be applied in the development of an Integrated Pest Management programme on cabbage.
Parasitism of Plutella xylostella (L.) (Lepidoptera:Plutellidae) Populations on Cabbage Brassica oleracea var.capitata (L.) by Cotesia plutellae (Kurdjumov)(Hymenoptera: Braconidae) in Ghana
(West African Journal of Applied Ecology, 2012) Cobblah, M.A.; Afreh-Nuamah, K.; Wilson, D.; Osae, M.Y.
The study was carried out at the Weija Irrigation Company site at Weija, in the Greater Accra Region of Ghana, to determine the seasonal abundance of the major parasitoid of Plutella xylostella (L.) populations on cabbage, Brassica oleracea var. capitata (L.) during the rainy and the dry seasons. The results indicated that Cotesia plutellae (Kurdjumov) was the most abundant and important parasitoid of P. xylostella on cabbage. It accounted for about 92% of the parasitoids, and occurred in all the three seasons of planting. The rest consisted of four facultative hyperparasitoids: Oomyzus sokolowskii, Aphanogmus reticulatus, Elasmus sp. and a Trichomalopsis sp., and two primary parasitoids, Pediobius sp. and Hockeria sp. A significantly higher rate of parasitism (68.6 ± 12.9%, P < 0.05) of P. xylostella by C. plutellae occurred during the major rainy season and the least (9.9 ± 7.1) in the minor rainy season. Cotesia plutellae acted in a density dependent manner, and its numbers increased as that of the host in all three seasons. The coefficient of correlation was highest in the major rainy season (r = 0.97) with a coefficient of determination of 0.97. In the minor rainy season r = 0.55, and in the dry season r = 0.66. The annual coefficient of correlation was r = 0.51 and the coefficient of determination = 0.262. Hence, in an annual production of cabbage, 26.2% of the variation in parasitism was due to the variation in the number of P. xylostella.The results, therefore, indicate that C. plutellae can be used in the development of an integrated pest management programme (IPMP), against P. xylostella in Ghana.
The role of termites in soil formation in the tropical semi-deciduous forest zone, Ghana
(Geografisk Tidsskrift, 2004-01) Awadzi, T.W.; Cobblah, M.A.; Breuning-Madsen, H.
Soil Macrofauna especially insects have been recognized as being an important factor in regulating soil processes and thereby the soil profile development. The influence of earthworms is well documented and it is the dominant member of the soil macrofauna influencing the soil formation processes in the temperate zone. In the tropics, termites and ants play the major role in the nutrient recycling and the movement and transportation of soil material. This paper describes the influence of termites on the soil formation in the tropical wet semi-deciduous forest in Ghana at the north coast of the Gulf of Guinea. The termites form distinct soil horizons especially at the summits of the landscapes where gravel free soil horizons are formed upon gravel rich horizons, and in some cases soil heaps are formed after the decomposition of huge trees.
Species Composition, Biology and Management of Sweet Potato Weevils (Cylas Species) In Southern Ghana.
(University of Ghana, 2000-09) Darko, S.Y.; Cobblah, M.A.; Wilson, D.D.; University of Ghana, College of Basic and Applied Sciences, School of Agriculture, Department of Crop Science
Species composition of sweet potato weevils (Cylas spp) on two sweet potato varieties was determined in the southern parts of the country. One species, Cylas puncticollis Boh. was found to be present in the southern part of Ghana. Studies on the biology of Cylas puncticollis were evaluated on two varieties, red and white varieties, under laboratory conditions at 27.0°C and 70% RH The incubation period of the eggs were 4 days on the red variety and 5 days on the white variety. Larval stages ranged from 10-11 days on the red and 10-12 days on the white. The pupal stage lasted 6-8 days on the red and 7-8 days on the white. Three larval instars were identified. Total developmental period from the egg stage to the adult stage ranged from 19-23 days on the red variety and 19-25 days on the white variety. Limited copulation significantly (P<0.05, t-test) increased oviposition and longevity periods of female weevils on both varieties. However, there was no significant difference in the number of eggs laid by females with limited copulation and those with unlimited copulation. Average percentage hatchability of eggs laid by females with limited copulation was 79.5 % and that of females with unlimited copulation was 85.7%. Cores from sweet potato [Ipomoea batatas (L.) Lam] root tubers (red and white varieties) were presented to Cylas puncticollis in choice- and no- choice bioassays. The red variety was significantly (P<0.05) preferred for oviposition in the choice bioassay. The effect of treatments (fertilizer, furadan, a combination of fertilizer and furadan) on sweet potato weevil populations was evaluated on two varieties in two separate fields. In both fields analysis showed that there was no significant difference (P>0.05, AOV) between the treatments on the weevils’ population. Treatment effect on weevils’ infestation (damage) of tubers on the two varieties was assessed during harvesting. The effects of the treatments did not differ significantly (P>0.05) from each other and from the control. However, furadan moderately reduced tuber infestation (damage) during the two planting seasons.
Suitability of four smoked fish species to Dermestes maculatus (De Geer) (Coleoptera: Dermestidae)
(Nigerian Journal of Entomology, Entomological Society of Nigeria, 2009) Zakka, U.; Ayertey, J.N.; Cobblah, M.A.
Suitability of tamarind and some selected crop seeds for the survival and development of Sitophilus linearis (Herbst) (Coleoptera: Curculionidae)
(International Journal of Biology, 2011) Adebayor, R.A.; Ayertey, J.N.; Cobblah, M.A.