Browsing by Author "Winnie Nanjego"

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Contrasting Effects of Shade Tree Species Diversity on Incidence and Damage of Pests and Diseases of Robusta Coffee
(Journal of Biology, Agriculture and Healthcare, 2024-01-31) Winnie Nanjego; Godfrey H. Kagezi; Samuel Kyamanywa; Judith Kobusinge; Geofrey Arinaitwe
In Uganda, most farmers grow their Robusta coffee, Coffea canephora in association with a diversity of shade tree species. Shade tree species diversity and density influence abiotic variables particularly, temperature and relative humidity. In turn, these may negatively or positively influence the population dynamics and damage caused by pest and diseases. Understanding these relationships is therefore vital for informing selection of shade tree species for ecological management of pests and diseases. We thus conducted a study in Kaweri Coffee Plantation Limited located in central Uganda to determine the effect of shade tree species diversity on the incidence and damage caused by pests and diseases on Robusta coffee. One plot measuring 100 x 100 m was demarcated in each of the four sections of the plantation: Kitagweta, Kyamutuma, Luwunga and Nonve. All the shade trees/shrubs and saplings (≤3 m) in the plot were counted and identified to species level. Additionally, incidence and damage of pests and diseases were assessed on 20 Robusta coffee trees selected along two diagonals in the plots. We recorded a total of 299 trees comprising of 22 species, with Solanum giganteum being the most abundant shrub (19.8 shrubs/ha) whereas, the most abundant shade tree species were Albizia chinensis (9.3 trees/ha) and Markhamia lutea (6.0 tree/ha). Eight (8) insect pests and two (2) diseases were recorded on Robusta coffee. These included, Xylosandrus compactus, Leucoptera coffeella, Leucoplema dohertyi, Epicampoptera andersoni, Prophantis smaragdina, Planococcus spp., Hypothenemus hampei, leaf eating beetles, Hemilleia vastatrix and Cercospora coffeicola. Our results further showed contrasting effects of shade tree species diversity on the incidence and damage of pests and diseases of Robusta coffee. Damage caused by X. compactus and E. andersoni as well as the incidence of H. vastatrix and C. coffeicola decreased significantly (p≤0.05) with increasing shade tree species diversity. Contrary, damage caused by all the other insect pests increased with increasing shade tree species diversity but, only significant (p≤0.05) in case of P. smaragdina, and Planococcus spp. There is therefore a need to thoroughly understand these dynamics if agroforestry systems are to be utilized as a strategy for ecological management of pests and diseases of Robusta coffee.
Within-Canopy Distribution of Incidence and Damage of Pests and Diseases of Robusta Coffee, Coffea Canephora and Implications for their Management
(International Journal of Sciences: Basic and Applied Research, 2024-03-03) Winnie Nanjego; Godfrey H. Kagezi; Samuel Kyamanywa; Judith Kobusinge; Geofrey Arinaitwe
Due to its perennial and robust vegetative growth nature, the Robusta coffee harbors a diversity of pests and diseases that are not necessarily evenly distributed within the coffee canopy and this has management implications. We thus, conducted a study in a Kaweri Coffee Plantation Limited in central Uganda to determine the distribution of incidence and damage caused by the pests and diseases within the Robusta coffee canopy. In each of the four section of plantation (Kitagweta, Kyamutuma Luwunga and Nonve), a plot measuring 100 x 100 m was demarcated and 20 Robusta coffee trees were systematically selected along two diagonals in each of the plots. All the stems on each of the selected coffee tree were assessed for pest and disease incidence and damage on the leaves, berry clusters and berries. The coffee canopy was divided into three sections (lower, middle and upper) and incidence and damage of the pests and diseases were determined on coffee leaves, berry clusters and berries. Results showed that the pests and diseases were not evenly distributed within the canopy. On the leaves, the incidence and damage caused by Leucoptera coffeella, Leucoplema dohertyi and Hemilleia vastatrix varied significantly (p≤0.05) across the canopy sections, with the highest levels (23.1, 36.1 and 30.5%) being recorded in the lower section. On the other hand, though the damage caused by Epicampoptera andersoni and the leaf eating beetles was not significantly (p≥0.05) different within the canopy, the highest infestation was recorded in the upper (26.9%) and middle (19.3%) sections, respectively. For the berry cluster, only damage caused by Planococcus spp. varied significantly (p=0.0188) across the canopy, with the highest infestation (18.6%) being recorded in lower section. However, incidence and damage caused by Prophantis smaragdina and Cercospora coffeicola were not significantly (p≥0.05) different within the canopy but, the highest levels were recorded in the upper section of the canopy (15.8 and 24.4%, respectively). On the coffee berries, the incidence and damage of both Hypothenemus hampei and Cercospora coffeicola did not significantly (p≥0.05) across the canopy sections but the highest levels were recorded in the lower (28.5%) and upper (20.7%), respectively. Our findings enlightened the understanding of the vertical distribution of the incidence and damage of pest and disease within the Robusta coffee canopy. This information will contribute to developing and implementing monitoring techniques and regimes as well as ecologically-informed management strategies for these pests and diseases.