ISSN: E 2347-226X, P 2319-9857

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Evaluation of Efficacy of different Disease Management Practices against sorghum covered smut (Sphacelotheca sorghi) at Fedis and Babile, Eastern Ethiopia

Samuel Tegene*, Fuad Abdusalam, and Zeleke Legesse

Fedis Agricultural Research Center, P.O. Box 904, Fedis, Ethiopia.

Corresponding Author:
Samuel Tegene
Fedis Agricultural Research Center, P.O. Box 904, Fedis, Ethiopia.

Received: 07/11/2013; Revised: 08/12/2013; Accepted: 19/12/2013

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Abstract

An experiment was conducted at Fedis and Babile for two cropping seasons (2011 and 2012) with the objective of evaluating the effectiveness of different seed treatment practices in controlling covered smut (Sphacelotheca sorghi) of sorghum. The materials tested were fermented cattle urine and botanical ‘‘Abeyi (Orm)’ (Maesa lanceolata). These materials were compared with fungicide Apron star as standard check and untreated seeds as control. Smut inoculated sorghum seed of variety Gubiye and Abshir were treated with aqueous extracts of the leaves of botanical ‘Abeyi (Orm)’at the rate of 20 ml extract diluted with the same amount of water; 200 g of the seeds were treated and then air dried before planting. The result showed that like the fungicides, both ‘Abeyi (Orm)’ and fermented cattle urine seed treatments significantly (P≤0.05) reduced the prevalence of disease more than the untreated checks for both varieties. Furthermore, statistically non-significant (P≤0.05) difference in grain yield was observed among the seed treatments. The grain yield for each treated varieties varied significantly (P≤0.05) as compared to the untreated controls. In general, the result clearly revealed that the use of M. lanceolata leaf extract and fermented cattle urine as a seed treatment against sorghum smut could be used as a substitute for fungicides and are potentially useful for resource poor farmers of lowlands of Eastern Hararghe Fedis, Babile and other areas with similar agro-ecology.

Keywords

Covered smut, sorghum, botanicals, leaf extract, cattle urine

Introduction

Sorghum (Sorghum bicolor) is the fifth most important cereal in the world after wheat, rice, maize, and barley. World production is between 55 and 70 million t of grain per annum from between 40 and 45 million ha. Sorghum is also one of the leading major food crops of Ethiopia. It ranks third in the country following maize and tef in total production and second to tef in ‘injera’ making [3,9]. Sorghum suffers from a lot of pests among which smut is the most important. Four distinct smut diseases of sorghum are recognized, they are Covered head smut induced by the fungus Sporisorium sorghi (Synonym Sphacelotheca sorghi), loose head smut induced by the fungus Sporisorium cruentum (Synonym Sphacelotheca cruenta), head smut induced by Sporisorium holci-sorghi (Synonym Sphacelotheca reiliana) and long smut attributed to the fungus described as Sorosporium ehrenbergii Kuhn though its generally accepted name since 1903 has been Tolyposporium ehrenbergii [19,21].

Smut was of major economic importance in sorghum-growing areas of the world in the early part of the 20th century. For example, the disease caused at least $400 000 annual losses in Kansas in the 1920s, while annual losses for the USA were estimated at $3 million tonnes [23]. Losses from S. reiliana in sorghum are 30-50% of yield [5,15,17,26]. Incidence ranged from 0-22% (average 2.9%) in a New Zealand survey [12]. Yield losses up to 80.4% have been reported in Romania [32]. In China, smut incidence on sorghum has been recorded up to 70% in continuous cropping plots [35]. Annual yield losses due to smut in Africa reaches 10% with localized losses of 60% or more [14]. The incidence of covered kernel smut varies from place to place, but in Ethiopia it was estimated to be about 50% [20,31].

The most important sources of inoculum for sorghum smut is seed. During threshing, spores get lodged on the surface of healthy sorghum seeds and are carried over to contaminate seeds. The disease is extremely seed borne and seedling infection occurs at the time of germination and emergence of seedlings [25,27] Field observations carried out in sorghum growing areas of lowlands of Eastern Hararghe, showed that smuts were the most important disease of sorghum and their incidence reached up to 50% under severe condition.

Several control measures have been recommended, all aimed at reducing disease damage to the crop. Seed dressing with fungicide is one of the cheapest and the most effective means of controlling seed and soil borne sorghum disease like smut. It is convenient for farmer’s use, improve stands and seedlings raised from treated seeds are healthier than those from un-treated seeds [11]. The widespread use of seed treatments has now virtually eliminated the disease from commercial hybrid grain sorghum in sorghum growing areas of the world. However, covered smut can still be a serious disease when seed treatments are not used, for example on small-scale farms [4,10,33]. The disease can be effectively controlled by thiram [34]. According to Akpa and Manzo [2] systemic fungicide, Apron plus 50% dust can reduce the risk of smut diseases. Similarly, Marley [18] also reported that metalaxyl and thiram based formulations gave better control of covered smut. Due to high cost and unavailability, usage of fungicides under small-scale farmers is very rare. Farmers over the years practiced the use of locally available botanical plants as bio-pesticide and other materials like cattle urine against different types of diseases on different crops [6].

Interestingly, African farmers are capitalizing on indigenous farmers’ technical knowledge (IFTK) for pest control. They prepare substances from concentrated hot peppers/chillies, neem leaves, Jimson weed (Datura stramonium Linn.), castor oil, papaya leaves and wood ash, clay, turmeric, wheat etc., to get rid of caterpillars, weevils, beetles, aphids, garden bugs and other pests [7]. The fact that synthetic pesticides are costly and often beyond the reach of the poor marginal farmers, calls upon taking a different approach based on research on the farmers indigenous technical knowledge which could ultimately lead to the development of bio-intensive IPM (integrated pest management), which will be economically feasible, socially acceptable and effective crop pest management strategies for the developing countries.

The use of resistant cultivars is one of the control measures employed for smut diseases. However, progress in this direction has been very slow in the developing agriculture in countries like Ethiopia. It has also been difficult to find cultivars with multiple resistances against all the major diseases. For this reason, this simple trial accomplished to investigate the efficacy of using seed treatment with locally available materials like fermented cattle urine and botanical ‘Abeyi (Orm)’; Kelewa (Amh) Maesa lanceolata Fresh leaf in comparison with fungicide Apron star with sorghum varieties of farmers preference for the effective management of smut diseases in the lowlands of Eastern Hararghe zone.

About 2000 species of plants are known to have pesticidal effects on crop pests [6,36]. Furthermore, use of fermented cattle and goat urine, sand, ash and other practices like use of botanicals are some of the weapons against field and storage pests. The natural products like urine, cow whey, clay, sand, etc. are often used in the developing countries to control the pests in the farm and storage where economic conditions limit the usage of the conventional pesticides as well as protectants [1]. On the other hand, farmers in the lowland areas of Eastern Hararghe were not accustomed to use these locally available materials in controlling sorghum smut. Literature on indigenous farmers’ technical knowledge (IFTK) in the world and especially in developing countries is scarce and poorly documented. Hence, a validation study on the effectiveness of the use of cattle urine and other lesser-exploited natural products as compared with fungicide against sorghum smut under Eastern Hararghe condition is important.

Therefore, this work was done to evaluate the effectiveness of leaf extract of indigenous plant Maesa lanceolata, and fermented cattle urine as compared to recommended fungicide Apron star in controlling sorghum smut. The use of botanicals and cattle urine in crop protection system avoids or reduces the use of synthetic chemicals, thereby making farmers less dependent on external inputs and create safe environment. The objective of this experiment was to determine the effectiveness of some locally available materials in relation to fungicide seed treatment to control covered smut on sorghum with the ultimate goal of developing effective, environmentally safe, culturally accepted and sustainable disease management practice.

Materials and Methods

General Description of the Experimental sites

The experiment on evaluation of efficacy sorghum smut management by seed treatments using fermented cattle urine and botanical ‘Abeyi’ Maesa lanceolata, as compared to Apron star was conducted at two potential sorghum producing areas of Eastern Hararghe namely: Babile and Fedis for two consecutive years in 2011 and 2012 in the main rainy season where sorghum smut was highly prevalent (Hot spot area). This experiment was accomplished under rain fed conditions, on Research field at Babile and Fedis of Eastern Hararghe zone, Ethiopia. The annual rainfall of these sites varied within the range 400 to 500 mm with erratic nature prevailing semiarid climate.

Climatic conditions in the study period

The meteorological data during the crop growth period recorded at meteorological observatory of the Research sub-station of Fedis is presented in the Figure 1 and Figure 2. However, these data were absent for Babile sub-station. The main cropping season for both stations lasts for six months and it is from July to December. The total rainfall during the crop growth periods were 408.8 mm and 459mm for 2011 and 2012 years respectively. Moreover, average minimum and maximum temperature of each months varied in the range of 7 to 14.5 and 24.6 to 28.6 respectively (Figure 2). It was observed that the total rain fall and the relative humidity for each month during the growing season was observed to vary in the range of 0 to 224.9mm and 26 to 70% respectively (Figure 1).

agriculture-allied-sciences-Amount-rainfall-mm

Figure 1. Amount of rainfall in mm and Relative humidity in % on monthly basis during the growing periods in 2011/2012

agriculture-allied-sciences-Maximum-minimum-temperature

Figure 2. Maximum and minimum temperature of Fedis area during the experimental period in 2011 and 2012

Treatments and experimental design

The land was prepared before the beginning of main rainy season. The treatments considered in the experiment were improved early maturing and striga resistant varieties of sorghum namely: Gubiye and Abshir, which have susceptible reaction to smut disease. These varieties are of farmers’ preference because of their resistance to striga and early maturity. Furthermore, smut inoculated seeds of these two varieties were dressed with a fungicide Apron star at a rate of one sachet (10 gm pack) for treating 4 kg sorghum seed. Besides, urine of cattle collected with a bucket and covered with plastic sheet and stored for seven days to allow fermenting. Then, it was mixed with water in 1:1 ratio. Smut inoculated 1 kg sorghum seed was inserted in 500ml fermented cattle urine +500ml water mixture allowed to stay for 30 minutes. Finally, the seed was taken out dried and sown. Inoculated sorghum seed was also treated with botanical ‘Abeyi’ at a rate of 20 ml fresh leaf extract per 200 g of seed as suggested by different authors [13,16]. Lastly, untreated smut inoculated sorghum seeds of both varieties were included to be used as a control. These eight treatments including controls were laid out in a factorial RCB design in three replications. Plot size of 4X5m was used. Planting was done at 50cm row spacing and 20cm plant spacing respectively. Three seeds were sown per hole and germinated seedlings were thinned to one plant per hill two weeks after emergency. Fertilizer rate of 75kg per hectare of DAP at planting and 50kg/ha of urea at booting were used. DAP was placed in between two hills at planting while urea was top dressed at booting in the presence of ample moisture in the soil. Weeding and earthening up was accomplished 2-3 times depending on the appearance of weed.

Data management and statistical Analysis

Data on days to heading was determined by monitoring the number of days when 50% of the plants in each plot bear a head. This was calculated from the days after sowing. The grain yield per plot was taken from matured sorghum heads from the three inner rows in each plot leaving the border plants. Then the harvested heads were sun dried, threshed and winnowed. The grain was weighed. The figures were converted to yield per plot, later converted to quintal per hectare. Smut incidence was recorded by counting the proportion of plants showing the symptoms and expressing the result in percentage. Smut severity at physiologic maturity was scored by looking the effect of the disease on the ten purposively taken diseased plants and considering the average of all plants using modified severity rating scale as used by Gwary et al. [8] as follows:

agriculture-allied-sciences-Smut-severity-rating

Table 1. Smut severity rating scale in 1-9

Analyses of Variance (ANOVA) of all quantitative data were accomplished using SAS computer software [24]. Duncan’s multiple range tests was used to separate treatment means [29]. Based on these treatments separation, the best treatment that significantly reduces disease incidence and resulted in better yield was selected.

Results

In this trial, both the seed treatments (using Abeyi and fermented cattle urine) tested controlled the disease invariably with the fungicide Apron star seed treatment (Figure 4 and 5). Disease incidence and severity revealed significant (P < 0.05) variation between treated seeds and controls for both sorghum varieties in both locations for both years (Figure 4 and 5). The highest disease incidence of 30.l% with a severity of 7.67 was recorded at Babile in 2011 on untreated Abshir. While the lowest incidence of 0% with severity of 1 was observed on both varieties treated with Abeyi, cattle urine and Apron star in both locations in 2011 cropping season (Figure 4). This clearly revealed that these locally available materials (fermented cattle urine and botanical Abeyi) could be used as a substitute for chemical fungicide Apron star in managing sorghum smut. Similarly, in 2012 disease prevalence with regard to the treatments showed nearly similar trend. Hence, the treatments used invariably controlled the disease. The treatments showed highly significant variation in contrast with untreated seeds of both varieties in both locations. The highest incidence of 30% with severity of 7.33 was observed on Gubiye at Fedis followed by an incidence of 28% with a severity of 7.67 on Abshir at Fedis (Figure 5). However, plots with treated seeds were observed to be free of the disease. This clearly revealed that seed treatment is crucial in managing this disease. Some of the untreated plots were observed to be highly affected by the disease that all the florets changed in to smut ending with limited normal seeds or yield (Figure 3).

agriculture-allied-sciences-Disease-incidence-plots

Figure 3. Disease incidence on plots sawn with untreated seeds

agriculture-allied-sciences-Incidence-Severity-Sorghum

Figure 4. Incidence and Severity of Sorghum varieties seed treated with different materials in 2011 at Fedis and Babile

agriculture-allied-sciences-different-materials-Fedis

Figure 5. Incidence and Severity of sorghum smut on seed treated with different materials at Fedis and Babile in 2012

Different authors confirmed the efficiency of fermented cattle urine and botanical ‘Abeyi’ in controlling sorghum smuts. A study by Adane and Gautam [1], clearly revealed that seed treatment with cow and goat urine, hot and cold water treatments besides Thiram and Apron plus except cold water were equally effective in reducing the incidence of both covered and loose smut on sorghum as compared to control. Furthermore, Sisay, Abebe and Wako [28], showed the effectiveness of fresh leaf extract of M. lanceolata (Abayi) in controlling covered smut of sorghum.

In this experiment, the incidence observed was attributed to the weather conditions during the seasons (Figures 1 and 2). Tarr [30] reported that high percentage of covered smut infection at field level was difficult due to the environmental condition such as soil temperature, moisture, soil pH, planting depth, fertilizer and emergency rate of host. According to Sisay, Abebe and Wako [28], for higher covered smut incidence, optimum temperature of 25°C and half moistened soil during planting are more important than other factors. The crop was more susceptible to the disease for about a week after planting. High temperature and low soil moisture encourage seed germination and discourage smut mycelium invasion of the germinated coleoptiles of the host plant. Meanwhile low temperature, moisture content of the soil and deeper planting of sorghum initiate high infection level [30].

There was non-significant (P < 0.05) variation among the grain yield of sorghum varieties treated with aforementioned treatments. This clearly revealed that the treatments were invariably controlled the disease resulting in similar yield regardless of the type of treatment. However, the grain yield for treated seeds varied significantly (P< 0.05) as compared to the untreated checks (Table 2). The ANOVA for the average combined yield for two years for both locations revealed that the highest yield of 33.7 and 35.11 quintal per hectare were recorded by Apron star treated sorghum seed of Abshir at Fedis and Babile respectively (Table 2). On the other hand, Gubiye treated with botanical ‘Abeyi’ yielded 32.5 quintal per hectare at Babile which was even better than the yield (29.63 quintals/hectare) of the same variety treated with Apron star at Fedis (Table 2). The lowest yield of Abshir 16.85 quintal/hectare at Fedis and 20.7 quintal per hectare at Babile were observed on untreated seeds of the variety respectively. The lowest yield of Gubiye 15.85 quintal/hectare at Fedis and 18.37 quintal per hectare at Babile were observed on untreated seeds of the variety respectively (Table 2).

agriculture-allied-sciences-Mean-combined-yield

Table 2. Mean combined yield of sorghum varieties sawn with different seed treatment to control sorghum smut at Fedis and Babile

Studies conducted by Adane and Gautam [1], on Sorghum (Sorghum vulgare Pers.) (soaked with urine for 20 min) witnessed reduced incidence of covered and loose smut by 90% and was comparable with conventional fungicides (Thiram and Apronplus). Furthermore, Pawar et al. [22] reported that five fungitoxicants viz., delan, deltan, apron star, vitavax and thiram + vitavax were used as seed treatment and foliar spray for the control of smut of pearl millet and sorghum. When these fungitoxicants were used as foliar spray to reduce the smut severity, no fungitoxicant could completely control the smut incidence. But when compared with control, treated plots indicated a significant disease control. Moreover, there was also significant increase in yield in all the treatments over control.

Conclusion and Recommendation

In general, this trial showed that M. lanceolata, fermented cattle urine and apron star significantly reduced the prevalence of smut disease as compared to the untreated controls and increased grain yield. Therefore, in areas where covered smut infection is high, M. lanceolata and cattle urine can be used to reduce or avoid the loss due to this disease. The use of M. lanceolata and cattle urine as seed treatment against sorghum smut is less costly and non-polluting and is potentially useful for resource poor small-scale farmers in the lowlands of Eastern Hararghe. These materials are locally available and environmentally safe. However, further study is required to determine the rate of application, the mechanism of control, the chemical responsible for such activity and their chemical and physical properties.

Acknowledgements

We thank Oromiya Agricultural Research Institute for funding this experiment. Crop process staff of Fedis Agricultural Research Center also deserve special thank for providing us their valuable comment and for their assistance in follow up and data collection during the accomplishment of the experiment.

References