Browsing by Author "Samuel Kyamanywa"

Now showing 1 - 4 of 4

Bean Leaf Beetle (Ootheca spp.) (Coleoptera: Chrysomelidae) Management via Planting Timing and Insecticides
(Insects, 2022-08-07) Charles Halerimana; Samuel Kyamanywa; Samuel Olaboro; Pamela Paparu; Stanley T. Nkalubo; John Colvin; Robert A. Cheke; Darren J. Kriticos; Michael H. Otim
Bean leaf beetles (Ootheca spp.) (Coleoptera: Chrysomelidae) are one of Africa’s most important pests of the common bean (Phaseolus vulgaris L.). Roots, leaves, floral parts, and young pods are all attacked, leading to a considerable loss in grain yield. In Uganda, there are no comprehensive prescribed management strategies for bean leaf beetles, but farmers typically try to control the pest by delaying bean crop sowing, and to a lesser extent, using insecticides. Although farmers have consistently implemented the two approaches, there is no information on the effects of the approaches in Uganda. To assess the impact of planting timing and insecticide spray regimes on bean leaf beetle populations, concomitant foliar damage, and grain yield, we set up trials in three agro-ecological zones with known presence of the beetles during the second rainy season of 2016 (2016) and the first rainy season of 2017 (2017). The first planting, coinciding with early planting, was conducted within one week after the onset of rains. The second planting, coinciding with mid planting, followed two weeks later, while the third planting, considered late planting in this study, was conducted one month after the second planting. A foliar application of cypermethrin commencing at 7 days after emergence (DAE), 14 DAE, 21 DAE, 28 DAE, and 35 DAE; a soil drench of imidacloprid at planting combined with a foliar spray starting at 7 DAE; and an untreated control were among the insecticide spray regimes evaluated. Higher bean leaf beetle abundance was recorded from mid-planting, while higher foliar damage was recorded from late planting in two of the three agro-ecological zones. However, higher marketable grain yield was recorded from early planting in all agro-ecological zones, suggesting that delayed planting may not be beneficial. Insecticide application reduced foliar damage and increased marketable grain yield, with a combination of soil drench and foliar spray resulting in much less foliar damage and, as a result, higher grain yield. However, this did not result in economic benefits. Furthermore, marketable grain yield was higher when insecticide spray regimes were combined with early planting in all agro-ecological zones during both seasons. Our findings suggest that the common bean should be planted early and that the control of the bean leaf beetle should target both the adults and the juvenile stages in the soil. Therefore, there is a need for farmers to be able to access less-expensive soil treatments.
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.
Host and Seasonal Effects on the Abundance of Bean Leaf Beetles (Ootheca spp.) (Coleoptera: Chrysomelidae) in Northern Uganda
(Insects, 2022-09-18) Moses Lutaakome; Samuel Kyamanywa; Pamela Paparu; Samuel Olaboro; Charles Halerimana; Stanley Tamusange Nkalubo; Michael Hilary Otim
Bean leaf beetles (BLBs) (Ootheca spp.) are serious legume pests in Uganda and sub-Saharan Africa, but their ecology is not well understood. We planted host plants, viz., common bean, cowpea, and soybean, in an experiment in the hotspot areas of Arua and Lira districts in Northern Uganda in order to assess their influence on the density of adults and immature stages of BLBs in different seasons. Overall, the number of adults, larvae, and pupae were higher in cowpea than common bean and soybean plots. The number of adults were highest in cowpea (29.5 adults/15 plants) in Arua during the long rainy season (2018A). The number of adults did not differ significantly during short rains (season B) in 2017 and 2018. Similarly, in Lira district, the highest number of adult BLBs was in cowpea (4.6 beetles) compared to the common bean (2.7 beetles) and soybean plots, with a peak at four weeks after planting (WAP). During 2018A, larvae of BLBs first appeared at five WAP and seven WAP and peaked at 13 WAP and 11 WAP in Arua and Lira, respectively. The pupae were present in the soil after the harvesting of crops during 2018A, but peaked at seven WAP and eight WAP in 2018B season in Arua and Lira, respectively. The occurrence of below-ground adults in 2018B followed the peak abundance of pupae, although this was delayed until six WAP in Arua compared to Lira. We conclude that cowpea is the most preferred by adults and larvae compared to common bean and soybean. Similarly, the first rain season (2018A) attracted higher abundance and damage than the second rain season. Management of the BLBs should thus take into consideration avoidance of host crop rotation and dealing with the below-ground stages.
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.