Crop Protection

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/50

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End date: 2019

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    PHENOTYPIC AND GENOTYPIC CHARACTERIZATION OF THE WHEAT STEM RUST PATHOGEN (Puccinia graminis f.sp. tritici) AND VARIETIES’ REACTION TO MAJOR STEM RUST RACES IN ETHIOPIA
    (Hawassa University College of Agriculture, 2019) TSEGA’AB TESFAYE WANORE
    Stem rust caused by Puccinia graminis f.sp. tritici (Pgt) is one of the most important diseases of wheat (Triticum aestivum) across the globe. Because of the sudden changes in stem rust race patterns, commercial varieties are becoming vulnerable globally at large and particularly in Ethiopia. The objectives of this study were to i) assess the distribution of wheat stem rust across selected major wheat producing regions of Ethiopia, ii) study population diversity of pgt races and iii) identify physiological race and the reaction of wheat genotypes to major races of the pathogen. For this purpose, a total of 464 wheat fields were surveyed in eight zones and 37 wheat producing districts of Amhara and Oromia regional states of Ethiopia. Besides, 60 disease samples were collected for race analyses using 20 differentials in a greenhouse trial and molecular diversity of the pathogen was studied using custom PgtSNP 3.0K chip. The reaction of 75 wheat genotypes and 1 universal susceptible check to major races of the pathogen was also evaluated in the greenhouse. Stem rust prevalence in the surveyed areas ranged from 0 to 100%, while disease incidences and severity varied between 0 and 25% and 0 and 11.5%, respectively. Greenhouse trials involving 20 differential cultivars resulted in the identification of three Pgt races (TKTTF, TTKSK and TTRTF) among the collected stem rust samples. Of these, TTRTF has not been previously reported in Ethiopia and hence, this is the first report of TTRTF in Ethiopia. Race TKTTF, also known as “Digalu race”, was the most frequent (75% frequency) of all the races of Pgt. The remaining two races TTKSK (Ug-99) and TTRTF were detected with frequencies of 4.16 and 22.91%, respectively. Eighty five percent of the stem rust resistance genes (Sr5, Sr21, Sr9e, Sr7b, Sr6 Sr8a, Sr9g, Sr9b, Sr17, Sr9a, Sr9d, Sr10, Sr38 and McN) were ineffective to all the races detected and 30% of the resistance genes were found to be effective to one or more of the races identified. However, in the present study only the differential host carrying Sr24 was effective to all the races identified in the study areas. The presence of the three Pgt races was also confirmed by molecular study, which categorized the isolates into three clades as I, IVB and IIIB for TTKSK, TKTTF and TTRTF, respectively. The resistance screening trial revelaed that five durum wheat genotypes namely Bichena, Tob-6, Assasa, Kokate and DW/NVT-LMA and six bread wheat genotypes namely, Sulla, Hidase, Wane, 36ESWY, ETBW 8459 and 36ESWYT were resistant against all the races at the seedling stage. These resistant genotypes can be used in wheat improvement programs after being checked under field condition for their adult stage resistance.
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    ECOLOGY AND MANAGEMENT OF BITING ANT, Tetramorium aculeatum MAYR (HYMENOPTERA: FORMICIDAE) IN COFFEE, Coffea arabica L. IN SOUTHWESTERN ETHIOPIA
    (Hawassa University College of Agriculture, 2019) SISAY KIDANU DEMMIREW
    Biting ant, Tetramorium aculeatum Mayr (Hymenoptera: Formicidae) is an important pest in coffee that affects farming activities in Southwestern Ethiopia. The objectives of this study were to assess farmers’ knowledge and pest management practices of biting ant understand the ecology of biting ant in Southwestern Ethiopia, and evaluate the efficacy and potential of some insecticides. Survey was conducted on 180 coffee farmers in 12 districts. Spatial distribution of biting ant was studied in eight coffee farms and analyzed by semivariance using geostatistics (GS+10). Nine insecticides treatments were evaluated both under ex-situ and in-situ conditions in CRD and RCBD designs, analyzed by analysis of variance. Most of the farmers interviewed (58.9%) recognize the problems of biting ant in coffee and some (23.3%) of them are knew this ant for about ten years. Significant variations were observed in the levels of infestation and abundance of the biting ant in different ecology of coffee producing districts and production systems. Lower altitudes and private coffee plantations had higher number of nests. The biting ants within coffee plant are aggregate on the tree. The semivariogram of the biting ant characterized with localized discontinuity and long range correlation in some coffee farms and vice versa in the others indicating spatial dependence of biting ant nests between samples pairs. The spatial distribution trends of the nest in the field showed aggregated along the center and in some farms near corners and declined from there across to the inner field. Under the ex situ evaluation, all the insecticide treatments caused significantly (p≤0.01) higher mortality (100%) of biting ants and caused complete mortality within 24 hours. Under field condition the insecticides showed significant variations on percent of evacuated nests. However, the two botanical insecticides, oxymatrine and nimbicidine, performed significantly (p≤0.01) as par with the other tested insecticides up to 18th day after application. On the other hand, deltamethrin 2.5% at the rate of 0.75ml/l of water caused significantly highest percent of evacuated nests and less number of newly constructed nests of biting ant (0.2) after thirty days of application. Generally deltametrin 2.5% at 0.75ml/l can be used for heavily infested farms where pruning and manually destructing the nest difficult and the future it is important to conduct insecticide evaluation with additional botanical based insecticides, and also undertake residual effect analysis of deltamethrin insecticide in coffee environment.
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    ASSESSMENT OF WEED SPECIES COMPOSITION AND THEIR MANAGEMENT PRACTICES IN ONIONAND EFFECT OFDIFFERENT WEED CONTROL METHODS IN ONION (Allium cepaL.)IN THE CENTRAL RIFT VALLEY OF ETHIOPIA
    (Hawassa University College of Agriculture, 2019) FEYISA BEKELE JIMA
    Farmers have lack of awareness on weed problem on the crop and under take only manual weeding option to control those weeds in their fields. The study identified weed species composition and their management practices in onion (Allium cepa L.) fields of Adami Tulu, Dugda, Lume, and Around Adama woradas, Central Rift Valley of Ethiopia. In addition the effect of different weed control methods in onion were evaluated in Meki woreda during 2017/2018 under irrigation. Primary data were collected from 200 individual farmers using structured questionnaires, face to face interview. Secondary data were collected from different literatures and reports, and analyzed using descriptive statistics, using SPSS version 20. Weed species compositions were determined in a quadrat count of 0.5m2 using systematic sampling techniques to obtain representative sample in the fields. The identified individual weed specieswere analyzed using quantitative means. Identified most problematic weed families wereAsteraceae (16 spp.), Poaceae (10 spp.), Solonaceae (2 spp.),Cyperaceae (2spp.)in descending order of 1st, 2nd, 3rdand4rd abundant weed families, respectively.The experiment was contained 13 different weed control treatments and laid down in randomized complete block design with four replicates. Collected data were analyzed using SAS version 9.0. The weed density varied significantly with the treatments (P<0.05). At 60 DAT the lowest weed density (41.875/m2) was recorded under HW3WAT followed by Oxyflourfen at 0.5L/ha + HW6WAT. At harvest the lowest weed density (30.875g/m2) was obtained under Oxyflourfen at 0.5L/ha+HW6WAT. The lowest weed dry weight was recorded from Pendimethalin at 1.5L/ha+HW9WAT (293.27g/m2). The highest weed controlefficiency(82.15%) was recorded under Pendimethalinat 1.5L/ha+HW9WAT followed by Oxyflourfen at 0.5L/ha+HW9WAT (80.48%) after weed free plot.The maximum plant height (43.47cm) was recorded in weed free plot followed by Oxyflourfen at 0.5L/ha+HW3WAT (40.68cm). But the number of leaves per plant has shown no significant difference with respect to different treatments (P>0.05). Maximum bulb diameter, bulb weight, bulb size (3.51cm, 122.58g, 73.25ml, 29.62ton/ha) were recorded respectively from weed free plot, which were statistically non-significant from Oxyflourfen at 0.5L/ha+HW9WAT). The lowest loss in yield (0.03%) was recorded in weed free check followed by plot treated with oxyflourfen at rate of the 0.5 L/ha + HW6WAT (6.8%) as compared to the highest yield obtained in plot treated with oxyflourfen at rate of the 0.5 L/ha + HW9WAT. Weed free check plot resulted in higher cost of protection and gross return but lower in net return and benefit: Cost ratio, whereas Oxyflourfen at 0.5L/ha and pendimethalin at 1.5L/ha showed highest Benefit: Cost ratio (20.34 and 14.65) respectively. The study showed that using herbicides alone or in combination with hand weeding is highly profitable than using hand weeding alone. Future studies on the use of herbicides with different rates and combinations with other methods, critical period of weed-control and more survey works in different onion production agro-ecologies are recommended.
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    VARIABILITY FOR YIELD, YIELD COMPONENTS AND QUALITY VARIABILITY FOR YIELD, YIELD COMPONENTS AND QUALITY VARIABILITY FOR YIELD, YIELD COMPONENTS AND QUALITY OF POTATO (Solanum tuberosum Solanum tuberosum L.), CULTIVARS TESTED TESTED IN CENTRAL ETHIOPIA
    (Hawassa University College of Agriculture, 2019) ABDU YASSIN
    This experiment was conducted in three replications of the randomized complete block design at Debre Birhan during 2017 main growing season to assess the nature and magnitude of variability in twelve potato cultivars for tuber yield and nutritional quality. There were highly significant differences among twelve cultivars in all characters, except in days to maturity. The highest and lowest total tuber yield was obtained from Bubu (36.86 t ha-1) and Dinkey (16.28 ton ha-1), respectively. Genotypic and phenotypic coefficient of variation ranged from 0.79 to 88.9% and from 0.84 to 92.43%, respectively. Heritability and genetic advance as percent of mean (GAM) ranged from 65.35% to 97.53% and from 1.63% to 183.52%, respectively. High heritability values were coupled with high GAM for all characters except for plant height, total carotenoids, starch content and tuber dry matter for which heritability and GAM were moderate. These values were low for days to maturity and tuber specific gravity. Most of the traits can successfully be improved through hybridization and selection. Total tuber yield ha-1 was positively and significantly correlated with marketable tuber yield, average tuber weight, plant height and starch content but was negatively correlated with iron and crude protein content at both genotypic and phenotypic levels. Maximum positive direct effect on total tuber yield ha-1 was exhibited by average tuber weight at genotypic level and by marketable tuber yield ha-1 at phenotypic level. Cluster analysis showed that the cultivars were grouped into five clusters. Cluster I was high in average tuber weight and starch content. Cluster-III was high in total carotenoids, crude protein, iron and zinc but low in total tuber yield ha-1corroborating the negative correlation between tuber yield and nutritional quality except Zn content. Results of this study demonstrated that there is sufficient genetic variability among the potato cultivars. However, it is difficult to make conclusion with one season and one location experiment. Therefore, it is recommended to evaluate more cultivars over locations and seasons to reach on more valid conclusion.
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    SURVEY OF TURCICUM LEAF BLIGHT (Exserohilum turcicum) ON MAIZE (Zea mays) AND EVALUATION OF MAIZE VARIETIES AND FUNGICIDE SPRAY FREQUENCIES FOR ITS MANAGEMENT
    (Hawassa University College of Agriculture, 2018) TAJUDIN ALIYI MOHAMMED
    Turcicum leaf blight (Exserohilum turcicum), TLB, is a major disease affecting maize (Zea mays) in western Ethiopia. This study was designed to: assess the incidence and severity of TLB in major maize growing agro-ecologies of Western Oromia, evaluate the reaction of maize varieties under production to TLB, and determine optimum propiconazole (tilt 250 EC) frequency as management option to TLB. Survey was conducted on 172 farmers’ fields in 29 districts and five zones of major maize growing agro ecologies in western Oromia region of Ethiopia. Survey results revealed the prevalence of TLB across all the districts even though at different levels. Mean TLB incidence ranged from 16.3% in Abay chomen to 96.67% in Wayu Tuka and mean percent severity index varied between 3.1% in Abay chomen and 57.5% in Lalo Assoabi district. TLB was relatively more severe on maize varieties BH-540, Limu and Kolba on surveyed areas. In addition, the effects of maize varieties, fungicide frequencies and their interactions on TLB development were assessed in a field experiment during the 2016/17 main growing season at Ambo Plant Protection Research Centre (APPRC). The experiment involved three maize varieties and three fungicide (Tilt, propiconazole) frequencies arranged in a factorial setting in randomized complete block design with three replications. TLB was initiated following artificial inoculation. Data were recorded on disease incidence and severity and severity scores were used to calculate area under disease progress curve (AUDPC) and infection rate. Grain yield and yield components were measured after harvest. Finally correlation and economic analyses were carried out. Disease parameters varied markedly across treatments, especially variety-fungicide combinations had a highly significant variation (p<0.01) in disease parameters. The highest terminal percent severity index (PSI) (86.7%), AUDPC value (2614.4 %-day) and disease progress rate (0.09339 units-day -1 ) were recorded on unsprayed variety AMHQ-760. On the other hand, the same variety had significantly lower disease level and gave the highest grain yield (9.424 t ha -1 ) when it was treated three times with propiconazole. TLB resulted in grain yield losses of up to 62.4% on AMHQ-760. PSI, AUDPC, incidence and disease progress rate were negatively correlated with yield and yield components. The highest marginal benefit (ETB 63,089 ha -1 ), and marginal rate of return (ETB 14.53) were obtained from variety AMHQ-760 with thrice application of propiconazole. Based on current results, three propiconazole applications were found effective to manage TLB even on susceptible maize variety. However, additional experiments should be carried out to verify the current results.
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    SURVEY OF ETHIOPIAN PEPPER MOTTLE VIRUSES IN THE CENTRAL RIFT VALLEY OF ETHIOPIA AND EVALUATION OF NETTING DURATION AS MANAGEMENT OPTION
    (Hawassa University College of Agriculture, 2018) KUMSA DIDA FAYE
    Ethiopian pepper mottle virus is one of the major constraints of pepper production in the central rift valley region of Ethiopia. The present study was conducted to assess the prevalence of Ethiopian pepper mottle virus in the region and to determine optimum netting duration for efficient protection of pepper from vector infestation and subsequent viral infection. For this purpose, field survey and an experiment was carried out in the central rift valley of Ethiopia. The survey was conducted on 60 pepper fields in three districts i.e. Butajira, Meki and Ziway districts. Data were collected on the incidence of viral disease, plant height and number of pods per plant. In addition, field experiments were carried out at Hawassa and Meki to assess the efficacy of netting duration against aphid vectors and viral diseases. Data were collected on the number of aphid populations, virus incidence, and pepper growth parameters and yield. Visual inspection of the surveyed fields revealed that almost all the pepper fields (99.6%) had viral diseases. Viral disease incidence ranged from 52.8% in Ziway district to 68.6% in Butajira district. Furthermore, significant variations at (p<0.01) were observed between treatments of the field experiments in terms of aphid infestation, virus incidence and pepper yield. Covering of plots with net for up to 60 or more days after transplanting reduced aphids’ populationper plant by a greater margin (61.8%-76.9% in Hawassa; 52.4-67% in Meki) and virus incidence by 48%-60.8% in Hawassa and 38.6%-48.5% in Meki as compared to the control plots. Total and marketable yields were significantly higher in plots protected by net for up to 60 days or more after transplanting while unmarketable yields were low in those plots. Low virus incidence and aphids’ population in plots covered by net up to 60 days after transplanting and longer resulted in increased yields by 44 %-55 % in Hawassa and 38 %-49.5 % in Meki as compared to the control plots. Unmarketable yield was positively correlated (p<0.001) with aphids population and virus incidence while total and marketable yields were negatively correlated with aphids population and virus incidence. The current results suggest the need to apply control measures at early growth stages to effectively protect pepper plants from aphids and associated viruses.