Effects of Buffer Zone and Inorganic Fertilizer Application on Transmission of Banana Bunchy Top Virus (Babuvirus Nanofarads) in Banana Fields in Northern Malawi

Abstract

Banana bunchy top disease causes yield reductions in bananas across the world, Malawi included. Yield losses of over 60% have been observed in Malawi due to banana bunchy top disease. This calls for effective agronomic management practices to manage the disease. A study was conducted in Mulanje and Nkhata-bay districts during the 2016–2017 season with the following objectives: (1) to evaluate the farmers' understanding and opinions regarding the prevalence and management of banana bunchy top disease; and (2) to ascertain the outcome of the effects of buffer zones and the application of inorganic fertilizer on the transmission of banana bunchy top virus (BBTV). In objective 1, in the districts of Mulanje and Nkhata-Bay, 76 randomly selected farmers were given a semi-structured questionnaire. The information gathered covered the five years' top crops, banana planting techniques, fertilizer types, knowledge of the banana bunchy top disease and suggested countermeasures, and difficulties in banana cultivation. The analysis of survey data was done using SPSS, and the Chi-square test was applied to check relationships between some variables. In objective 2, a field trial was set up at Chintheche and Mpamba sites in Nkhata-Bay district in Malawi in the 2016–2017 growing season. The experiment had a split plot layout with four replicates and a randomized complete block design, with a buffer zone as the main plot element and inorganic fertilizer as the subplot. Treatments consisted of four buffer zones based on the distance from the infected plants (2-10 m radius, 50m radius, 100m radius, and planting where the infected banana plants were removed without a resting period) and two levels of inorganic fertilizer (no inorganic fertilizer control and application of 56.6 kg of NPK (23:21:0+4S) per ha plus 46 kg of urea per ha. Plant height, the number of leaves per plant, the number of suckers per plant, the prevalence of illness, the length, and width of the leaves were all recorded. To determine whether BBTV was present in leaf samples, an enzyme-linked immunosorbent assay (ELISA) was performed. GenStat was used to examine the data collected using analysis of variance (ANOVA), and means were separated using the least significant difference (LSD) test at P 0.05. Bananas were the most prevalent crop in Mulanje (30.8%) and Nkhata-bay (50%) over the preceding five years, while crop production was the main source of income for the farmers in Mulanje (65.4%) and Nkhata-bay (94.0%), respectively. According to the survey, the disease, which is one of the main obstacles to banana production, was known to most farmers (55.4% in Mulanje and 63% in Nkhata-bay). Additionally, many farmers (30.7% in Mulanje and 48.0% in Nkhata-bay) claimed to have managed the disease by following the suggested procedures. The survey also showed that banana bunchy top disease had caused a 15–30 ton per hectare yield reduction xiv in bananas. The survey also revealed that the yield of bananas had been reduced by 15 to 30 tons per hectare due to banana bunchy top disease. Most of the farmers (64.5%) in both Mulanje and Nkhata-bay reported that they lacked alternative sources of clean planting materials. It was also indicated that most farmers (67.4%) both in Mulanje and Nkhata-bay got information on recommended control measures from public extension works. Farmers reported that uprooting infected banana plants was labor-intensive. The buffer zone had a significant effect (P 0.05) on disease incidence at 12 and 28 weeks after planting at the Chintheche site and at 28 weeks after planting at the Mpamba site. Planting banana plants at a radius of 100 m away from the infected plants had a lower disease incidence than planting at a radius of 2 m to 10 m away from the infected banana and planting where the infected banana was uprooted without a resting period. Application of inorganic fertilizer significantly reduced disease incidence at Chintheche 12 weeks after planting. The buffer zone, inorganic fertilizer, and their interaction had an effect (P 0.05) on disease incidence in both sites at 28 weeks after planting. Higher disease incidence (49.5% and 25.4%) in Chintheche and Mpamba, respectively, was observed in plots planted at a radius of 2 to 10 m from infected bananas and not supplied with inorganic fertilizer. Plots located at a radius of 100 m away from the infected banana plants and not supplied with inorganic fertilizer recorded lower disease incidence (0.9% and 0.5%) in Chintheche and Mpamba, respectively. Plant height, number of leaves per plant, number of suckers per plant, leaf length, stem diameter, and leaf width were significantly increased by the application of inorganic fertilizer. The study showed that banana bunchy top disease was a significant barrier to banana output in the Mulanje and Nkhata-bay areas. The farmers perceived the recommended control measure to be labor-intensive. A buffer zone of 100 m away from infected banana plants and the application of inorganic fertilizer increased plant growth and reduced BBTV transmission. Therefore, Malawi can control the banana bunchy top disease by establishing vast buffer zones and using inorganic fertilizer