Browsing by Author "Eden-Green, S."
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Item Banana Xanthomonas wilt: a review of the disease, management strategies and future research directions(African Journal of Biotechnology, 2007) Biruma, M.; Pillay, M.; Mwangi, M.; Muchunguzi, P.; Nyine, M.; Turyagyenda, L.; Eden-Green, S.Banana production in Eastern Africa is threatened by the presence of a new devastating bacterial disease caused by Xanthomonas vasicola pv. musacearum (formerly Xanthomonas campestris pv. musacearum). The disease has been identified in Uganda, Eastern Democratic Republic of Congo, Rwanda and Tanzania. Disease symptoms include wilting and yellowing of leaves, excretion of a yellowish bacterial ooze, premature ripening of the bunch, rotting of fruit and internal yellow discoloration of the vascular bundles. Plants are infected either by insects through the inflorescence or by soil-borne bacterial inoculum through the lower parts of the plant. Short- and long-distance transmission of the disease mainly occurs via contaminated tools and insects, though other organisms such as birds may also be involved. Although no banana cultivar with resistance to the disease has been identified as yet, it appears that certain cultivars have mechanisms to ‘escape’ the disease. Management and control of the disease involve methods that reduce the inoculum’s density and spread of the pathogen. Removal of the male bud (de-budding) has proven to be very effective in preventing the disease incidence since the male bud appears to be the primary infection site. The economic impact of banana Xanthomonas wilt is not fully understood but its impact on food security in the region is very significant. While germplasm screening for the disease is ongoing, efforts to genetically engineer resistance in some banana cultivars are also making good progress. This paper presents a review of the disease and management strategies that have been successful in curtailing its spread.Item The Effect of the Prompt Removal of Inflorescence-Infected Plants and Early Debudding of Inflorescences on the Control of Xanthomonas Wilt of Banana(ISHS Acta Horticulturae, 2007) Blomme, G.; Turyagyenda, L.F.; Mukasa, H.; Ssekiwoko, F.; Mpiira, S.; Eden-Green, S.Xanthomonas wilt of banana, caused by Xanthomonas campestris pv. musacearum, is an important constraint to banana production in Uganda. Different strategies to control the disease were investigated in an attempt to identify those methods that could be used by small farmers in East Africa. The effect of removing pseudostems showing early and late symptoms of inflorescence infection on the spread of the disease in ‘Kayinja’ (syn. ‘Pisang Awak’, ABB genome) was studied. Suckers of ‘Kayinja’ did not become infected when pseudostems derived from the same mat were removed at an early stage of inflorescence infection. In addition, the results of experiments to determine the effectiveness of bagging and debudding inflorescences at different stages to prevent insect-borne infection are reported. This research was undertaken using ‘Kayinja’, mixed plantings of East African highland cultivars (AAA) and high-yielding exotic/improved cultivars in farmers’ fields. ‘Kayinja’ was the most susceptible cultivar to floral infection, followed by the East African highland cultivars. Exotic/improved cultivars had the lowest number of infections. Lower numbers of floral infections may be attributed to the persistence of male flowers and bracts. No flower infection was observed on plants that were debudded immediately after the formation of the last cluster and on those that were bagged until the formation of the last cluster and debudded right after. However, plants that were bagged until the formation of the last hand, but not debudded, or debudded after 2 weeks or more, showed high levels of inflorescence infection. This indicates that insect-vector transmission occurs only via the male parts of the inflorescence. Prompt removal of the whole pseudostems showing symptoms of early inflorescence infection and early debudding are simple, cheap, easily applicable and highly effective methods for controlling Xanthomonas wilt. Results of a cost-benefit analysis of control options are discussed.Item The effectiveness of different herbicides in the destruction of banana Xanthomonas wilt infected plants(African Crop Science Journal, 2008) Blomme, G.; Turyagyenda, L.F.; Mukasa, H.; Eden-Green, S.Early detection followed by the destruction of infected mats is one of the recommended and effective methods of controlling banana Xanthomonas wilt. As manual destruction is very tedious and time consuming, herbicide injections in the pseudostem or the stump were evaluated as a suitable alternative. The study was carried out in Luwero district in central Uganda. Herbicide injections were made on ‘Pisang Awak’ plants (Musa ABB group) using different concentrations of Roundup and 2,4-D at a pseudostem height of 30 and 100 cm. In addition, the herbicide was injected in the centre (diameter-wise) and in the peripheral part of the pseudostem (tangentialwise). Herbicide applications into the stump were also evaluated. All plants (100%) injected with 2,4-D had fallen and started rotting by three weeks after application. However, at three weeks, none of the plants treated with Roundup, regardless of the concentration and the height of injection had died. Similarly plants injected with 2,4-D had less re-sprouting compared to plants treated with Roundup. Therefore, 2,4-D is more effective than Roundup in destroying ‘Pisang Awak’ plants and in suppressing the re-sprouting of lateral shoots. Since 2,4-D is also cheaper than Roundup it is recommended for use on small-scale plantations. At least 1.6 ml of the original concentrate of 2,4-D and 2.0 ml of the original concentrate of Roundup needs to be applied per mature plant. The most effective pseudostem injection height was found to be 100 cm. The angle of injection whether peripherally or central and the plant growth stage did not affect the herbicides’ efficiency. The results also showed that pseudostem injections are more effective than stump herbicide applications.Item Rehabilitation of Banana Farms Destroyed by Xanthomonas Wilt in Uganda(J. Appl. Biosci, 2008) Turyagyenda, L.F.; Blomme, G.; Ssekiwoko, F.; Karamura, E.; Mpiira, S.; Eden-Green, S.The measures that have been recommended for banana wilt management in Uganda include debudding, disinfection of garden tools and destruction of diseased plants. However, the adoption rate for these options has been low and the disease has reached epidemic levels. Destruction and removal of the infected plants followed by a fallow period or planting of a crop that is not a host of Xcm, and subsequent replanting with healthy banana suckers could restore banana plantations in areas affected by wilt. This study was carried out to determine the most effective method of destroying infected plants and an appropriate fallow period to ensure replanted suckers are not reinfected. Trials were carried out at three field sites with 68-76% of mats infected at the beginning of the experiment. Treatments evaluated were: (1) killing plants by injecting a herbicide (2,4-D) into the pseudo-stems; (2) plants manually cut down and their rhizomes dug out; (3) plants cut down at ground level and re-sprouting suckers continuously mechanically removed. The banana plant debris was piled on ridges between the plots. Replanting with healthy banana suckers started one month after clearing the diseased plants, using tissue culture plantlets of cultivar Pisang Awak and Mpologoma. A portion of the field was replanted each month up to eight months after the onset of the trials. An economic viability analysis of the different options of destroying infected plants was carried out. Banana suckers planted after a one-month fallow period had a 25% survival rate, while all suckers planted after seven and eight months of fallowing survived. Generally, more dead plants were recorded with cv. Mpologoma than cv. Pisang Awak. Incidence of re-infection was highest in the plots where re-sprouting suckers were being continuously removed and lowest in plots where plants had been completely uprooted. A fallow period of at least six months is required to restore health to farms after infection by Xanthomonas wilt. Complete uprooting of infected plants and removing plant debris onto ridges is the best option for managing Xanthomonas wilt. However, the economic viability analysis indicated that farmers preferred to use herbicide to kill the plants rather than uprooting which is more laborious and expensive. The use of herbicide is hence recommended followed by a 6 month fallow or crop rotation period.Item Spread of Xanthomonas campestris pv. musacearum in Banana (Musa spp.) Plants Following Infection of the Male Inflorescence(ISHS Acta Horticulturae, 2008) Ssekiwoko, F.; Turyagyenda, L.F.; Mukasa, H.; Eden-Green, S.; Blomme, G.Xanthomonas campestris pv. musacearum (Xcm) causes Xanthomonas wilt of banana (Musa spp.) and enset (Ensete ventricosum) in East and Central Africa. The disease is spread by insects that visit the male inflorescence, through the use of infected planting materials and by contaminated garden tools. To evaluate the most appropriate control options, the spread of bacteria within the plant following natural flower infection was studied in Luwero and Mpigi districts of central Uganda. Banana tissue samples were collected from the corm, true stem and leaf sheaths of ‘Pisang Awak’ (ABB genome) and ‘Matooke’ (AAA genome) mother plants, showing four progressive stages of disease development: stage 1 – male bud wilting; stage 2 – decaying rachis; stage 3 – premature fruit ripening; and stage 4 – rotting of fruit bunches. Thirty plants were sampled per stage and per cultivar. Additional samples were taken from attached suckers. Bacteria were isolated from surface-sterilized plant samples and identified by colony characteristics on a semi-selective medium. Following inflorescence infection, Xcm moved along the true stem, into the youngest leaf sheaths inserted on the true stem, down into the corm and into the older leaf sheaths. At early stages of inflorescence infection (stage 1), bacteria were restricted to the upper parts of the true stem in ‘Pisang Awak’, but had moved further down the stem in ‘Matooke’. Therefore, cutting down mother plants at stage 1 could stop Xcm from reaching the corm and eventually crossing to the suckers of ‘Pisang Awak’ but this was less likely to be effective for ‘Matooke’ plants. The bacteria were recovered from suckers of both cultivars showing symptoms at stage 4, but at stage 3 only from ‘Pisang Awak’. It is recommended that whole mats should be completely uprooted or killed by herbicides in case mother plants show symptoms beyond stage 1 for ‘Pisang Awak’ and at all disease symptom stages for ‘Matooke’.