Browsing by Author "Muyinza, H."

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    Effect of Grain Splitting on Biology and Development of Callosobruchus Maculatus (Coleoptera: Bruchidae) in Storage
    (Uganda Journal of Agricultural Sciences, 2013) Muyinza, H.; Komurembe, M.; Lugoloobi, A.; Musitalla, G.; Aguti, G.
    Bruchids belonging to Callosobruchus spp. Order Coleoptera are the main storage loss causative pests on cowpea grains in East Africa. Losses have been estimated to be as high as 5-15 % within a few months of storage at farmers’ level. In this study the effect of grain splitting on the biology of C. maculatus was investigated. The cowpea grain treatments compared included split grains + no testa, split grains with testa, compared with whole un-split cowpea grains. Gravid female 4-day old C. maculatus were allowed to oviposit on the cowpea grain which had been pre-conditioned to 12% moisture content, then removed. Data on oviposition, adult eclosion and weights of emergent adults were collected over 3 weevil development generations. Mean separations were done using Analysis of Variance. There was significant reduction (P< 0.05) in oviposition and emergent adults for C. maculatus at F1, F2 and F3 generations on spilt compared to whole grains. Mean oviposition levels on split grain without testa was with only 1.3 ± 1 eggs compared to 258 ± 14 eggs in the controls at F3. Oviposition levels reduced with generation time in all the treatments. The control had the highest adult weevil emergence and mean adult weevil weights (78.8 ± 6.9) with no emergent adults from completely split grains at F3. Mean weevils were highest in the controls and reduced with generation time with least adult weights from the split grain. In this study we conclude that grain splitting reduces development of C. maculatus spp. and could be a viable option in the integrated management of this bruchid pest during storage at farmer level.
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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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    Modeling the Potential Geographical Distribution and Ecological Niche of Selected Fruit Fly (Diptera: Tephritidae) Species in Uganda
    (Journal of Plant and Pest Science, 2015) Isabirye, B.E.; Masembe, C.; Akol, A.M.; Muyinza, H.; Rwomushana, I.; Nankinga, C.K.
    Despite their overwhelming economic importance, efforts to assess the distribution of fruit flies (Diptera: Tephritidae) in Uganda have been minimal. Consequently, in this study, potential geographical distributions and climatic envelopes of 10 selected fruit fly species were modeled. Two presence-only predictive models namely, Maxent and Bioclim, were run using 19 bioclimatic parameters at a resolution of 30 arc seconds. New detections and existing records of fruit flies were used in the model. The climatic profiles of the selected fruit flies were described and the relative importance of the bioclimatic variables was explored. There was a close agreement between the two models about the distribution and suitability patterns matching the main fruit agro ecological zones. Precipitation (PC-1 = 61.4190%) and temperature (PC-2 = 29.214%) significantly shaped fruit fly niches across the country. Central and mid north zones provided the most suitable niches, while the western, northeastern and areas around Albert Nile were characterized as marginally suitable. The models were mostly robust in performance (AUC: 0.815 – 0.974), with model test performance ranging from random (C. capitata: 0.486) to excellent (C. cosyra: 0.965). Predicted marginal sites, such as higher altitude zones matched negative areas of the models, which reflected higher model prediction abilities. These results provide an initial insight into the bioclimatic tolerance ranges of fruit flies in Uganda and should assist in identification of sites for future sampling efforts and fruit fly management planning.