Volume 6 Special Issue 1 2012
Plant science and biotechnology in Ethiopia

ISBN 978-4-907060-09-1

How to reference: Mekonnen SA, Haile F (2012)Essential Oil Content Response of Lemongrass, Palmarosaand Citronella to Post Harvest Wilting and Chopping. In: Mekonnen SA (Ed) Plant science and biotechnology in Ethiopia. The African Journal of Plant Science and Biotechnology 6 (Special Issue 1), 1-4

Guest Editor

Solomon Abate Mekonnen

CONTENTS AND ABSTRACTS

Solomon Abate Mekonnen, Fikiremariam Haile (Ethiopia) Essential Oil Content Response of Lemongrass, Palmarosaand Citronella to Post Harvest Wilting and Chopping (pp 1-4)

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Original Research Paper: An experiment was set to determine effects of wilting period and chopping on essential oil content of three aromatic grasses vis. Cymbopogon winterianus Jowitt, C. citratus Stapf and C. martinii. A completely randomized design with three replications was used in the experiment. Wilting the harvested part of C. citratus, C. winterianus and C. martinii for 96 hr yielded significantly higher essential oil (av. 1.31, 2.44 and 1.45%, respectively) than other treatment levels, except for 72 hr. Chopping to any level generally reduced essential oil content by 20.9% for C. citratus, 8.9% for C. winterianus and 9.24% for C. martinii. Thus, commercial production of essential oils from these plants needs to consider these two factors in order to optimize the quality and yield.

Beemnet Mengesha Kassahun, Solomon Abate Mekonnen (Ethiopia) Effect of Cutting Position and Rooting Hormone on Propagation Ability of Stevia (Stevia rebaudiana Bertoni) (pp 5-8)

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Original Research Paper: To fill in existing information and knowledge gaps on asexual propagation of stevia (Stevia rebaudiana Bertoni), this experiment was conducted at the Wondo Genet Agricultural Research Center nursery site in a plastic chamber. The experiment consisted of two levels of cutting positions (top and middle) and three levels of rooting hormones (zero hormone, 0.2% indole-3-butyric acid (IBA) and 0.4% 1-naphthalene acetic acid (NAA)). The experiment was laid out in a 3×2 factorial arrangement in a randomized complete block design with three replications. Data on leaf number/plant, survival count and rate were recorded and analyzed. Mean squares from analysis of variance revealed the existence of a very highly significant influence (P < 0.001) of cutting position on leaf number and survival rate. The application of rooting hormone exerted a significant influence (P < 0.05) on survival rate only. Interaction effect of cutting position and hormone application did not exert an influence (P > 0.05) on the parameters considered. Higher but statistically similar survival rate were recorded for the control and the 0.2% IBA treatment whereas the lowest values were recorded for the 0.4% NAA treatment. Top cuttings demonstrated significantly more leaves (eight) and survival rates (80.18%) and showed a 46.78 and 28.49% increase in leaf number and survival rate compared to middle cuttings. Therefore, it is recommended that the top part be used for the propagation of stevia. The application of rooting hormone might not necessarily be an economically sound option for vegetative propagation.

Zewdinesh Damtew Zigene, Beemnet Mengesha Kassahun, Tsion Tesema Ketaw (Ethiopia) Effects of Harvesting Age and Spacing on Leaf Yield and Essential Oil Yield of Rosemary (Rosmarinus officinalis L.) (pp 9-12)

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Original Research Paper: A study was conducted to evaluate the effect of harvesting age and spacing on agronomic and chemical traits of rosemary (Rosmarinus officinalis L.). Data on plant height, branch number/plant, fresh and dry leaf weight/plant, fresh and dry leaf yield/ha, essential oil (EO) content and EO yield/ha were collected and analyzed. Harvesting age exerted a very highly significant (P < 0.001) influence on plant height and dry leaf weight/plant, and a highly significant (P < 0.01) influence on dry leaf to stem ratio. Spacing affected fresh and dry leaf weight/plant very highly significantly (P < 0.001) and highly significantly (P < 0.01) plant height. The interaction effect of harvesting age and spacing was significant (P < 0.05) on dry leaf yield/ha, EO content and yield, and highly significant (P < 0.01) on fresh leaf yield/ha. Maximum plant height and dry leaf weight/plant were obtained 11 months after transplanting (MAT) and maximum dry leaf to stem ratio at 9 MAT. Higher plant height was attained at 60 × 60 cm while higher fresh and dry leaf weight/plant at 90 × 90 cm. Higher fresh leaf yield/ha (38.43 t) and dry leaf yield/ha (10.83 t) were obtained at 60 × 60 cm at 9 MAT. Maximum EO content (2.77 %) and EO yield (271.43 kg) were recorded at 10 MAT at a spacing of 90 × 120 cm and 60 × 60 cm, respectively.

Solomon Abate Mekonnen (Ethiopia), T. P. S. Katiyar, H. Ravishankar (India) Yield Components and Yield of Haricot Bean (Phaseolus vulgaris L.) Under Different Irrigation Frequency and Planting Density Treatments (pp 13-20)

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Original Research Paper: An experiment was undertaken to determine the yield component and yield of haricot bean (Phaseolus vulgaris L.) varieties in the semi-arid region of Dire Dawa, Ethiopia. The experiment was a split plot with three irrigation frequencies as main plots and a combination of three planting densities and two haricot bean varieties as subplots, all of which replicated three times. Irrigation frequencies consisted of 1, 0.67, and 0.5 irrigation water to cumulative pan evaporation (IW/CPE ratio) thereby fixing the depth of IW to 60 mm, planting densities of 15.6, 25, and 35.7 (plants m⁻²) and two haricot bean varieties, ‘Roba-1’ and ‘Mexican-142’ were considered. Different planting densities were employed by changing planting distances within cultivation rows. Plant data on dry biomass/plant, number of branches bearing pods, number of pods/primary branch, number of pods/plant, pod length and width, number of beans/pod, number of beans/plant, 100-bean weight and harvest index at harvest were recorded. Increasing irrigation frequency from 0.5 IW/CPE to 0.67 IW/CPE and to 1 IW/CPE significantly increased all parameters. On the contrary, increasing population densities caused a significant reduction in the parameters. Averaged over planting density and variety, yield/ha and soil water depletion increased significantly with the increase in irrigation frequency. These results showed that irrigation given at 1 IW/CPE can give maximum yield of both haricot bean varieties in the semi-arid condition of Dire Dawa.

Zerihun Yemataw, Hussein Mohamed, Mulugeta Diro, Temesgen Addis (Ethiopia), Guy Blomme (Uganda) Genetic Variability, Inter-Relationships and Path Analysis in Enset (Ensete ventricosum) Clones (pp 21-25)

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Original Research Paper: Enset (Ensete ventricosum (Welw.) Cheesman) is the most important staple food crop for millions of people living in southern and southwestern Ethiopia. Two hundred and forty enset clones collected from six zones in the southern region were established in 1999 at the Areka Agricultural Research Center to assess the magnitude of genetic variability, heritability of important characters, inter-relationships among characters and their direct and indirect effect on yield. The mean squares due to genotypes were highly significant (P ≤ 0.01) for all the quantitative traits studied, suggesting the presence of substantial variability among the 240 enset clones. The phenotypic and genotypic coefficients of variation varied from 16.4% for plant height to 147.2% for bulla yield ha^-1 y^-1 and from 12.92% for pseudostem height to 138.41% for bulla yield ha^-1 y^-1, respectively. Estimates of H’ were lowest for fiber yield plant^-1 (43.06%) and highest for maturity time (93.75%). The minimum genetic advance expectations were for pseudostem height (19.65%) and the maximum were for bulla yield ha^-1 y^-1 (267.35%). Fermented, squeezed kocho yield ha^-1 y^-1 was positively and significantly correlated with most of the traits, but negatively correlated phenotypically and genotypically with maturity time, bulla yield plant^-1 and fiber yield plant^-1. Path coefficient analysis indicated that leaf sheath weight after decortication and central shoot weight before grating exerted positive direct effects on fermented, squeezed kocho yield ha^-1 y^-1. A wide variation was observed between maximum and minimum values for most of the characters. The presence of wide variation in observed traits may point to opportunities for selecting enset clones with desirable characters.

Yared Semahegn Belete, Sentayehu Alamerew Kebede, Adugna Wakjira Gemelal (Ethiopia) Genetic Associations of Seed Oil Quality Traits and Selection Criteria in Ethiopian Mustard (Brassica carinata A. Brun) (pp 26-29)

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Original Research Paper: Ethiopian mustard, as an oil seed crop, needs genetic improvement which integrates both quality and agronomic traits. In this study, the correlations of eight quality traits of the 36 genotypes were investigated using a 6 × 6 simple lattice design at Holetta Research Center, Ethiopia. Heritability and genetic advance (as percent of mean) of the studied traits ranged from 35.4-69.2 and 5-23.8%, respectively. A strong positive correlation (0.752) was observed between palmitic and erucic acid. Similarly, a strong but negative correlation (-0.866) was observed between oleic and erucic acid. In relation to agronomic traits, positive and significant correlation of stearic with number of primary branches (0.607), number of secondary branches (0.608) and number of pods (0.387) was observed. Palmitic showed negative correlation with seed yield/plot (-0.354), oil yield/plot (-0.393) and 1000-seed weight (-0.404). Oil content positively correlated with seed yield/plot (0.343) and oil yield/plot (0.446), while negative correlation was found with days to flowering (-0.373) and days to maturity (-0.394). Path analyses showed that oleic acid and oil content were found the most important components to be considered as selection criteria in the improvement of edibility of seed oil of Ethiopian mustard genotypes. This investigation also indicated that improvement in the oil content of the seeds of the genotypes would be possible through selecting early flowering genotypes.

Beemnet Mengesha Kassahun, Hassen Nurhusain, Hailesilasie Gebremeskel, Solomon Abate Mekonnen, Zewdinesh Damtew, Muluken Philipos, Bekri Melka, Terutaka Niide (Ethiopia) Participatory Development of Quality Seedlings in Lemon Verbena (Alloysia triphylla L.) Using Stem Cuttings (pp 30-33)

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Original Research Paper: This experiment fills in existing information and knowledge gaps on asexual propagation of lemon verbena by involving two farmer’s research groups (FRGs) at Sembero Rogicha and Dawile Kebeles during 2011 starting from the beginning of August to the end of October. Each FRG has 10 member farmers. The experiment consisted of three levels of the part used (top, middle and bottom) and four levels of node number (three, five, seven and nine) in a factorial combination. The nursery experiments were laid out in a randomized complete block design with three replications. Data on survival count, survival percentage, number of branches/seedling, number of leaves/branch and number of leaves/seedling were recorded in a participatory approach. Mean squares from analysis of variance revealed the existence of a very highly significant influence (P < 0.001) of cutting position, node number and the interaction effect of cutting position with node number on all parameters considered in the study. Bottom cuttings with 3 and 5 nodes demonstrated significantly higher respective values of survival rate (81.67 and 78.33%), number of branches/seedling (6), number of leaves/branch (25) and number of leaves/seedling (104 and 137) and lowest values of these parameters were recorded for top cuttings. Similar results were obtained with the FRG member farmers’ evaluation criteria. Therefore, bottom cutting position with 3 and 5 nodes could be recommended for the development of quality lemon verbena seedlings using stem cuttings under good nursery management.

Solomon Abate Mekonnen (Ethiopia) Irrigation Frequency and Plant Density Affect Phenology and Crop Growth of Haricot Bean (Phaseolus vulgaris L.) (pp 34-39)

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Original Research Paper: A field study was conducted involving a factorial combination of two haricot bean (Phaseolus vulgaris L.) varieties ‘Roba-1’ and ‘Mexican-142’ with three irrigation frequencies at 60, 90 and 120 mm cumulative pan evaporation (CPE) using an IW/CPE ratio thereby fixing the depth of irrigation water (IW) to 60 mm and three planting density levels (150000, 250000, 350000 plants/ha) to investigate their effects on phenology and crop growth at Tony farm, Dire Dawa during the winter (‘Bega’) season of 2002. A split plot design was laid out with irrigation frequency as main plots while a combinations of planting density and variety as sub-plots with three replications each. Increasing irrigation frequency from 120 to 90 and to 60 mm CPE significantly increased days to maturity and crop growth parameters of haricot bean. Variety significantly influenced phenological stage, specifically days to flowering and days to maturity. Plant height and leaf number were significantly higher for ‘Mexican-142’, with a 17.7 and 29.0% increase, respectively. Increasing plant density significantly (P < 0.05) decreased leaf area and leaf number, and increased leaf area index of beans. The highest seed yield per plant was recorded with the minimum plant density, 150000 plant/ha and lowest seed yield per plant with the highest plant density, 350000 plants/ha. The increase in irrigation frequency from 120 to 60 mm CPE significantly increased seed yield per plant from 38.22 to 59.94 g.

Mihiret Mekonnen Moges, Tanta val Selvaraj, Mitiku Tesso Jebessa (Ethiopia) Influence of Some Antagonistic Bacteria against Early Blight (Alternaria solani (Ell. & Mart.) Jones & Grout.) of Tomato (Lycopersicon esculentum Mill.) (pp 40-44)

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Original Research Paper: Early blight caused by Alternaria solani (Ell. & Mart.) Jones & Grout., is amongst the most common foliar disease in tomato (Lycopersicon esculentum Mill.) farms of West Shewa sub-regions of Ethiopia that reduce yield and occasionally cause complete crop loss. To satisfy the contemporary market driven demand and supply for tomato products, the research need to focus on management options that are environmentally friendly. The present study was undertaken to evaluate the antagonistic effect of some rhizospheric bacteria (biocontrol agent) against A. solani and to study their influence on growth and development of tomato leaf of a farming cultivar, ‘Romans VS’. Ten local antagonistic bacteria were screened in vivo for suppressing the pathogen. Five promising antagonists exhibiting higher zone of inhibition (ZOI) (38 mm and above) and percent disease control (ranging from 38.16 to 43.79%) were selected. These are Pseudomonas fluorescens TK-1, P. fluorescens TK-3, Bacillus subtilis TK-4, P. fluorescens TK-8 and P. fluorescens TK-10. The greenhouse experiment revealed P. fluorescens TK-3 as a best biocontrol agent which increased plant height by 35.20% and biomass by 52.28%. The efficacy test results of antagonistic bacterial isolates have clearly indicated that the indigenous strain, P. fluorescens TK-3 followed by Bacillus subtilis Tk-4 is an efficient biocontrol agent against A. solani with good in vitro and in vivo antagonistic activity.

Meseret Degefa Regassa, Ali Mohammed, Kassahun Bantte (Ethiopia) Evaluation of Tomato (Lycopersicon esculentum Mill.) Genotypes for Yield and Yield Components (pp 45-49)

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Original Research Paper: Owing to the limited availability of improved cultivars that are suitable for different purposes, the yield of tomato in Ethiopia is far below the world’s average. The world’s average was 34.84 tones/ha and the average productivity of Ethiopian was 7.57 tones/ha (FAO 2009). Hence, identification of improved tomato varieties that are adaptable, high yielding and disease resistant are necessary. Therefore, an experiment was conducted at Jimma University College of Agriculture and Veterinary Medicine (JUCAVM) to evaluate nine tomato (Lycopersicon esculentum Mill.) varieties for their fruit yield using a Randomized Complete Block Design (RCBD) with three replications under field conditions. Data were collected on growth parameters and yield components, including plant height, primary branch, number of flowers and fruit per cluster, number of fruit clusters per plant, days to first harvest, fruit set percentage, polar and equatorial diameter, number and yield of fruit per plant, marketable, unmarketable and total fruit yield per hectare. The study indicated that yield per plant was higher for ‘H-1350’, ‘Eshet’, ‘Metadel’, ‘Marglobe’ and ‘Moneymaker’ than the rest of the varieties. Total yield was highest for ‘H-1350’, ‘Eshet’, ‘Metadel’, ‘Marglobe’ and ‘Moneymaker’ whereas it was lowest for ‘Fetan’, ‘Miya’ and ‘Jimma local’. Considering yield and yield components, variety ‘H-1350’ was found to be better than the rest of the varieties, while ‘Eshet’, ‘Marglobe’ and ‘Jimma local’ were the poorest performers for almost all parameters.

Meseret Degefa Regassa, Ali Mohammed, Kassahun Bantte (Ethiopia) Evaluation of Tomato (Lycopersicon esculentum Mill.) Genotypes for Fruit Quality and Shelf Life (pp 50-56)

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Original Research Paper: Soft fruit such as tomato has a very short post harvest shelf life. Accordingly, information and knowledge gaps on post-harvest handling, fruit quality and storability of tomato (Lycopersicon esculentum Mill.) aggravate the situation. Therefore, an experiment was conducted at Jimma University College of Agriculture and Veterinary Medicine to evaluate the fruit quality and shelf life of nine tomato varieties. Major fruit physicochemical properties, including fruit weight, volume, juice, weight loss, total soluble solids content (TSS), acidity (TTA and pH), TSS/TTA ratio and sensory attributes, which were assessed at 7-day intervals during a 28-day storage period, were collected. There was an increasing trend in physiological weight loss observed during the study period, during which physiological weight loss was highest in ‘Eshet’, ‘Marglobe’ and ‘Jimma local’. Changes in TTA during storage were relatively small. The TTA content showed a decreasing pattern throughout the storage period. A general decreasing trend in fruits firmness and an increase in fruit color were observed among the varieties as the storage period progressed. Considering fruit quality and shelf life, variety ‘H-1350’ was better than all other varieties while ‘Eshet’, ‘Marglobe’ and ‘Jimma local’ were the poorest performers in almost all parameters.

Tewabech Tillahun (Ethiopia), Jaime A. Teixeira da Silva (Japan), Solomon Admassu (Ethiopia) Assessment of Yield Loss and Determination of Optimum Planting Date for the Control of Gray Leaf Spot on Maize (Zea mays L.) in South Ethiopia (pp 57-61)

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Original Research Paper: Maize (Zea mays L.) is one of the most important strategic crops selected for food security mainly due to its high productivity and wider adaptability in Ethiopia. In recent years, gray leaf spot (GLS) has become a serious disease in different parts of the country. However, no research activity has been carried out to determine the role of planting date on the control of GLS. Therefore, the objectives of this study were to assess the damage and yield loss due to GLS and to identify and determine the optimum plating date of maize for the control of GLS. The experiment was carried out at Areka and Billito, Southern Ethiopia which are GLS hotspots during the 2004-2006 main cropping seasons. Fungicide treatment as the main plot and planting dates as the subplot treatment were arranged in a split plot design and replicated four times. The result of this experiment shows that there were significant differences among planting dates, fungicide spray, years and locations. Analysis of variance carried out across years at Areka and Billito indicated that there were statistically significant differences among planting dates for severity, upper ear leaf infestation, number of cobs harvested, number of diseased cobs, ear length, ear diameter, grain yield and 1000-kernel weight. The highest grain yield (8.12 and 9.09 t ha^-1) was recorded from plantings on March 17 and April 18 at Areka and Billito, respectively. Planting on March 27 and April 18 increased yield by 55.5 and 43.0% more than maize planted on April 17 and May 18 at Areka and Billito, respectively. The highest grain yield (8.61 t ha^-1) was recorded in plots sprayed with fungicide at Billito while the least was recorded in unsprayed plots (6.3 t ha^-1) at Areka. The yield loss due to late planting was 29.5% more than early planting.

Zewdinesh Damtew Zigene, Bizuayehu Tesfaye, Daniel Bisrat (Ethiopia) Growth and Essential Oil Yield of Artemisia (Artemisia annua L.)as Affected by Growth Stage (pp 62-65)

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Original Research Paper: A study was conducted to observe the growth trend and essential oil yield of Artemisia annua L. under varying growth ages at the Wondo Genet Agricultural Research Center. The experiment consisted of six growth stages (2, 3, 4, 5, 6 and 7 months after transplanting). The treatments were arranged in randomized complete block design with three replications. Data on plant height, branch number/plant, fresh leaf weight/plant, dry leaf weight/plant, fresh leaf/stem ratio, dry leaf/stem ratio essential oil content (EOC) and essential oil yield (EOY) were collected and analyzed. As mean squares from analysis of variance indicated, different growth ages affected plant height, fresh leaf/stem ratio and dry leaf/stem ratio very highly significantly (P < 0.001) and affected EOC and EOY highly significantly (P < 0.01). Fresh leaf weight/plant and dry leaf weight/plant were affected significantly (P < 0.05) by different growth ages. Branch number/plant did not vary significantly (P > 0.05) at different age of growth. In this study, the highest values were recorded at 5 months after transplanting (MAT) for plant height (194 cm), fresh leaf weight/plant (382.47 g) and dry leaf weight/plant (98.36 g) and at 2 MAT for fresh leaf/stem ratio (0.69) and dry leaf/stem ratio (0.64). The highest EOC (1.08%) and EOY (21.78 kg) values were obtained at 6 MAT.

Getaneh Nigatu, Tsegaye Bekele, Woldeyohannes Fantu (Ethiopia) Impact of Moisture Content and Mound Size on Recovery and Quality of Charcoal from Prosopis juliflora (SW.) DC. in Rift Valley of Ethiopia (pp 66-72)

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Original Research Paper: Determining recovery and quality of charcoal is crucial in Ethiopian conditions where wood-fuel deficit is very high and depletion of acacia woodlands is increasing. The objectives were to investigate the recovery and yield of charcoal per m³ of round wood, and quality of charcoal produced from Prosopis juliflora at different moisture content of wood and sizes of traditional earth-mound kiln. The study was conducted by producing charcoal from a naturally grown P. juliflora forest in Rift Valley of Ethiopia. 63 m³ of stacked green and 63 m³ air-dried woods were carbonized at 5, 7 and 9 m³ kilns. Quality parameters (proximate value, gross heat value, friability, burning rate, bulk density, spark ignition and smokiness) of charcoal were determined. The result showed a mean recovery of 33.5% and 35% from green and air-dried wood, respectively. Average minimum and maximum yield of charcoal per m³ were 200.9 kg and 227.4 kg from the air-dry and green wood of 9 and 5 m³, respectively. Moisture content of wood significantly influenced (P < 0.05) most quality parameters but the difference was non significant (P > 0.05) for recovery, ash content, bulk density and burning rate. Mound size did not significantly affect (P > 0.05) both recovery and all quality parameters. Generally, the quality of charcoal was affected by the moisture content, but mound size did not affect both recovery and quality of the charcoal produced from P. juliflora.

Zewdinesh Damtew Zigene, Beemnet Mengesha Kassahun (Ethiopia) Agronomic Characteristics and Essential Oil Yield of Palmarosa (Cymbopogon martinii (Roxb.) Wats) as Affected by Population Density and Harvesting Age at Wondo Genet, Southern Ethiopia (pp 73-75)

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Short Communication: A study was conducted to evaluate the effect of harvesting age and population density on agronomic characteristics and essential oil yield of palmarosa (Cymbopogon martinii (Roxb.) Wats). Data on number of tiller/bunch, number of leaf/bunch, fresh weight/bunch, fresh herbage yield/ha, dry weight/bunch, dry herbage yield/ha, essential oil (EO) content and EO yield/ha were collected and analyzed. Population density exerted a very highly significant (P < 0.001) influence on fresh herbage yield/ha, dry herbage yield/ha and essential oil yield/ha of palmarosa. A very highly significant (P < 0.001) influence of harvesting age was observed on number of leaves/bunch, fresh weight/bunch and fresh herbage yield/ha while a highly significant (P < 0.01) effect was observed on EO yield/ha. Dry weight/bunch, dry herbage yield/ha and EO content was affected significantly (P < 0.05) by harvesting age. Maximum fresh herbage yield/ha (20.86 t), dry herbage yield/ha (6.85 t) and EO yield/ha (100.65 kg) were obtained at 60 × 60 cm spacing for harvests made at every 3 months after plating and the preceding harvests. Higher and statistically similar EO content were obtained for harvests made at every 3, 4 and 5 months after planting regardless of spacing.

Zenebe Mekonnen Gebretsadik (Ethiopia) The Effect of Slope on Diameter and Height Growth of Grevillea robusta at Wondo Genet, Southern Ethiopia (pp 76-79)

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Short Communication: Grevillea robusta (A. Cunn. ex R.Br.)is widely used in Africa and grows on fairly well drained and neutral to acidic soils in altitude ranging 0-3,000 m a.s.l. but does not tolerate water logging or heavy clays. In Ethiopia, it does well in agro-climatic zones ranging 1,500-2,700 m a.s.l. In this study, three south facing slope categories with mean slope in degree and mean slope length in meters {(15, 50); (8, 70); (4, 100)} are selected coincidently in ten-year old G. robusta plantation perpendicular to the contour. Ten trees at each slope range are selected randomly. The objectives of the study were i) to identify the slope factor on height and Diameter at Breast Height (DBH i.e.1.3 m above the ground) growth of G. robusta trees and ii) to compare responses of apical and lateral growths of trees on three slope categories to give reasonable assurance of detecting meaningful differences. The statistical analysis from one-way ANOVA at α = 5% has shown that there is highly significant difference (P < 0.0001) in height growth of G. robusta planted on different slope ranges. Similarly, it was also recognized that there is significant difference (P < 0.04) in lateral or diameter growth of G. robusta trees planted at hillsides of Abaro Mountain at Wondo Genet.

Ermias Shonga, Temesgen Addis, Mesele Gemu, Tesfaye Tadesse (Ethiopia) Cassava Scale: A New Threat for a Food Security Crop in Ethiopia (pp 80-83)

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Research Note: In Ethiopia, cassava is mainly cultivated and consumed in Segen Peoples, Gedeo, Gamo Goffa, Sidama and Wolyita zones of the southern region. Farmers in these areas grow cassava as a food security crop in small irregular scattered plots either alone or intercropped with different crops. However, production and productivity of the crop is seriously affected by cassava scale, Aonidomytilus albus. It was first observed in 2001 at Amaro, Southern Ethiopia. It has become important to integrate various information on cassava scale in order to grow cassava sustainably. Therefore, this study was conducted to determine the distribution of A. albus, to identify alternate hosts and natural enemies and to test hot water temperatures against it. Scale insects were collected from cassava stems and buds and stems of different crops and sent to IITA, Benin for identification. Different hot water treatments for different time durations were tested to disinfest cassava cuttings from cassava scale. Cassava scale was recorded in Segen peoples, Gedeo, Sidama and Wolyita zones. It was recorded on Solanum incanum, Abitilion tiophreslium, Buzuwa and Nuxia congesta. Scale samples taken from the stems of Grabilia robusta, Melia azadirachta and Erytrina abyssinica were identified as Coccus sp., Parlatoria camelliae and an undetermined species, respectively. Cybocephalus sp., which is a predator of scale insects including whiteflies, was recorded at Amaro at two locations. Boiling water treatment at all durations totally killed cassava cuttings. Relatively better germination of cassava cuttings were obtained at 55°C. However, complete removal of cassava scale was not possible.