Browsing by Author "Akol, A. M."

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    Fruit Fly (Diptera: Tephritidae) Host Status and Relative Infestation of Selected Mango Cultivars in Three Agro Ecological Zones in Uganda
    (Informa UK Limited, 2015-10-09) Isabirye, B. E.; Akol, A. M.; Muyinza, H.; Masembe, C.; Rwomushana, I.; C. K. Nankinga
    Despite their economic importance, there is paucity of knowledge on fruit fly host status in Uganda. Therefore, this study set out to profile the host range of the main fruit fly pests and determine the susceptibility of selected fruits and mango cultivars across three main mango agro ecological zones, which included: Western Medium High Altitude Farmlands (WMHF), Lake Victoria Crescent (LVC), and the Northern Moist Farmlands (NMF) in Uganda. A wide range of fruits was sampled across the three zones. These were incubated at the National Agricultural Research Laboratories following standard protocols. Emerging fruit fly species were identified using standard keys and counted. Among the sampled fruits, 633 (35.0%) individual fruits from 15 plant families were positive for fruit fly infestation. Bactrocera invadens dominated (76.3%) of the positive samples, while infestation by native species, such as Ceratitis capitata and Ceratitis cosyra, was negligible. Annonaceae, Solanaceae, Rutaceae, and Anacardiaceae plant families recorded significantly more host species, while the number of pest fruit flies (species richness) per plant species followed a similar trend: Solanaceae > Rutaceae > Anacardiaceae. There was significant (P < 0.0001) variability in infestation among mango fruit cultivars, both within and across zones. When all zones were pooled together, Tommy Atkins and Kent, and Keitt, Kate, and Biire were the least and most infested, respectively. In conclusion, fruit flies have a diverse range of commercial and non-commercial hosts in Uganda. Strategies for fruit fly pest eradication in the country should ensure elimination or management of alternative fruit hosts and integration of tolerant mango cultivars in fruit development programs.
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    Geometric Morphometrics of Geographic and Host-Associated Population Variations of Bactrocera Invadens in Uganda
    (AGRICULTURE AND BIOLOGY JOURNAL OF NORTH AMERICA, 2014) Isabirye, B.E.; Masembe, C.; Nankinga, C. K.; Muyinza, H.; Akol, A. M.
    Fruit flies (Diptera: Tephritidae) are among the most economically important pests of edible fruits worldwide. Because of the cryptic nature of most species in Bactrocera complex, it is not clear whether allopatric and host associated speciation has taken course among B. invadens populations in the different zones in Uganda. This would be important in the design of efficient management strategies. The morphological variation of 3 allopatric and host-associated populations of B. invadens was studied using Euclidean distance matrix analysis and variance structure coordinate system geometric morphometrics techniques. Size and shape were analyzed throughout 15 landmarks for 360 specimens after symmetrization process. Host type significantly affected wing size and shape (P = 0.0001), with CVA showing host population discrimination with very high degree of population classification (95.03%) accuracy. Mango wings were significantly smaller than tropical almond, but the former did not significantly differ with guava. Similarly, mean wing size and shape among the three zones differed significantly (P = 0.000). B. invadens from the WMHF had relatively bigger wings, while the NMF recorded the smallest wings. CVA discriminant functions showed a very high degree of zonal population classification (95.48%) accuracy. LVC population wing shape was significantly different from NMF (P = 0.000) and WMHF (P = 0.000), while the latter two were also different (P = 0.000). There were significant differences in allometry and developmental instability fluctuating asymmetry among fruit hosts in the order: mango > guava > almonds. The results have added to the evidence that geographic and host-associated adaptation can produce reproductive isolation and produce ecotypes. The ability of B. invadens to undergo rapid ecological evolutionary radiations might affect the efficiency of common control methods, and our results should help to recast fruit fly management strategies.
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    Oviposition Preference and Offspring Performance in Phytophagous Fruit Flies (Diptera: Tephritidae): The African Invader, Bactrocera invadens
    (International Research Journal of Horticulture, 2013) Akol, A. M.; Masembe, C.; Isabirye, B.E.; Kukiriza, C. K.; Rwomushana, I.
    Behavioral choices have been hypothesized to reflect fine-tuned evolutionary adaptation by the preference-performance hypothesis (PPH), which states that female insects will evolve to oviposit on hosts on which their offspring fare best. The extent to which this is true in the African invader, Bactrocera invadens (Diptera: Tephritidae) was assessed in this study. Five host-plant species: Terminalia catappa (Combretaceae), Persea americana (Lauraceae), Psidium guanjava (Myrtaceae), Mangifera indica (Anacardiaceae), and Citrus sinensis (Rutaceae), and 11 mango varieties: Tommy, Zillatte, Keitt, Kent, Kagogwa, Apple, Palvin, Dodo, Kate, Biire and Glen, were tested for their conformity to the PPH. The fruits were incubated, larvae reared, and the adults maintained on an artificial diet in the laboratory. There was significant variability in host species (P = 0.038) and variety (P = 0.015) preference in the orders: T.catappa > P.guanjava > M. indica > C. sinensis > P.americana; while Glen & Biire and Zillate & Tommy were the most and least preferred varieties, respectively. Offspring performance (development rate, survival, weights and sex ratio) differed significantly and followed a very similar trend only that for fruit species P.americana performed better than C. sinensis. The relationship between host preference and the offspring performance measures showed strong support for the PPH with overall coefficient of determination of 75.4% (P = 0.000) and 65% (P = 0.003) for host species and varieties, respectively. This study has generally increased the knowledge on the role of host species and varieties on the biology of the pest and re-affirmed the growing credence that host-specific variation in adult performance has an important role in shaping host preference of phytophagous insects, as proposed by PPH.