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Volume 5 Number 2 February 2019

Influence of Abiotic Factors on the Population of Serangium Parcesetosum; A Predator of Cassava Whitefly in Uganda


Authors: Wamani S. ; Acipa A. ; Opio M. S. ; Ocitti P. ; Wanyana B. ; Byalebeka J.
Pages: 31-37
DOI: doi.org/10.32861/jac.52.31.37
Abstract
Whitefly is a known pest of economic importance in the cassava production systems of Africa. This pest has been reported to cause losses to cassava through direct feeding damage as well as vectoring cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). Serangium parcesetosum is a known predator of whitefly (Bemisia tabaci) and previous screenhouse and laboratory studies reported that temperature affected the reproduction and survival of this predator. However, these findings lacked precision since they did not depict the field situation. In that regard, it was imperative to initiate a study to help understand the influence of abiotic factors especially temperature and rainfall on the population of S. parcesetosum in the cassava growing fields of Uganda. The study was conducted in two agro-ecological zones of Uganda, namely; North Western Savannah Grassland (Lira) and the Kyoga Plains (Kamuli) in the first rains of 2017. Results revealed that temperature caused an increment of 3.5%, 9.1% (Kamuli) and 1.1%, 1.8% (Lira) for mean adult and larvae S. parcesesotum per plant respectively. On the contrary, rainfall caused a decrease in the population of S. parcesesotum in Lira. Generally, the effect of both temperature and rainfall on the predator population in the field was minimal.

Effect of Spacing and Topping on the Performance of Hydroponically Grown Tomato Under Tropical Conditions


Authors: Alex Williams Ayarna ; Satoru Tsukagoshi ; George Oduro Nkansah ; Kazuya Maeda
Pages: 23-30
DOI: doi.org/10.32861/jac.52.23.30
Abstract
Production of tomato in the tropics especially in Ghana is beset with lots of setbacks thereby causing low yields per hectare. Greenhouse cultivation systems are promising yet yields of tropical tomato cultivars are hampered by adverse temperature conditions. In order to mitigate this, an experiment was conducted during the extreme summer temperature conditions in the greenhouse at Kashiwanoha Campus of Chiba University, Japan. The study was conducted between May 23, 2018 and September20, 2018. The low substrate volume production system of 500mL in closed recirculated hydroponics (sub-irrigation) method was employed. Three tropical tomato cultivars (Jaguar, Lebombo and Lindo) were evaluated for yields. Plants were spaced at 20cm (4.2 plants m-2) and 30cm (2.8 plants m-2). At 7 and 9WAT, plants were topped at 2nd and 4th nodes respectively. The 3x2x2 factorial in Randomised Complete Block design in three replications was adopted. Some parameter collected were; 1. Morphometrics such as plant height, girth, leaf number and chlorophyll content, days to 50% flowering and fruit set 2. Yield components and fruit quality such as fruit number, marketable yield, yield per area, yield per hectare, percent blossom end rot, fruit TSS, TA, TSS/TA ratio and 3. Dry matter partitioning at last harvest, 11WAT. Results showed that blossom end rot reduced the yields of Jaguar and Lindo almost by 50% while Lebombo recorded less than 1%. Lebombo produced significantly the highest plant dry mass of 125g of which 57.7% was converted to vegetative growth compared to the Jaguar. For Jaguar however, 53.7% of total plant dry mass was allocated to fruits. This in effect was translated to the highest yield of 93tons ha-1 year-1 for Jaguar plants that were pinched at 4th truss in high density planting of 4.2 plant m-2.

Growth and Yield Response of Maize (Zea mays L.) To Different Weed Control Methods in the Western Highlands of Cameroon


Authors: Foncha Felix ; Bame Irene Bonsiysi ; Wirnkar Lendzemo Venasius ; Nsuh Konje Christina ; Etta Cletus Nkongho ; Mbong Grace Annih ; Petentsebenkwange Valentine Nchinda ; Mafouasson Apala Hortense ; Suh Christopher ; Noe Woin
Pages: 15-22
DOI: doi.org/10.32861/jac.52.15.22
Abstract
Weed control is an important agronomic practice that improves growth and maximizes yield in maize. An experiment was carried out to investigate the ‘effect of different weed control methods on the growth and yield of maize (Zea mays L.) in the western highlands of Cameroon. The work was carried out during the 2017/2018 main cropping season from the 14th of March to the 14th of July at the Institute of Agricultural Research for Development (IRAD) Bambui experimental field. The experiment was laid out in a Randomized Complete Block Design (RCBD) and replicated three times. The experiment comprised of seven treatments: weedy check or control (T1), constant hand hoeing (T2), delay hand hoeing (T3), pre-emergence herbicide application of   Atrazine 90 DF ( 0.9 kg  ha-1) (T4), post-emergence herbicide application of Ultramais 100 SC (1.9 litre ha-1) (T5), pre- herbicide application of Atrazine 90 DF ( 0.9 kg  ha-1) + Ultramais 100 SC (1.9 litre ha-1) (T6) and delay post-emergence herbicide application of Ultramais 100 SC (1.9 litre ha-1) (T7). The white maize variety CHC 201 (“KASAI”) was used during the experiment and sown in plot sizes of 4 m x 5 m with a planting density of 80cm by 50cm with 2 plants per station with the aim of achieving a plant population of 50,000 plants ha-1. All agronomic practices were followed from planting to harvesting. The data recorded were plant height, number of green leaves per plant, leaf area, stem girth, days to 50% tasseling, days to 50% silking, ear height, ear length, ear girth, number of gain rows per ear,  number of gains per ear, 1000 grain weight and grain yield.. The data collected were analyzed with the aid of STATGRAPHICS Plus 5.0 Software and ANOVA was run to find the differences between the various treatments. The highest 1000 grain weight (314.13g) came from the pre-emergence plus post-emergence herbicide application treatment and did not differ significantly (P˃0.05) from the constant hand hoeing treatment (307.83g). The lowest 1000 grain weight (234.67g) was seen in the weedy check treatment. The constant hand hoeing had the highest grain yield (6.27 ton ha-1) and this did not differ significantly (P˃0.05) from the pre-emergence plus post-emergence herbicide application treatment (6.07 ton ha-1). The lowest grain yield (3.18 ton ha-1) was seen in the weedy check treatment. From the study, the pre-emergence plus post-emergence herbicide application may be recommended for increasing maize yield particularly in the case of high scale production.