Efficacy Evaluation of Different Foliar Fungicides for the Management of Wheat Strip Rust (Puccinia striiformis) in West Shoa Zone, Oromia, Ethiopia

Rust is one of the most widespread and devastating disease of cereal crop all over the world. This study was conducted to evaluate the efficacy of different fungicide against strip rust of wheat (Puccinia striiformis) at Toke Kutaye District, West Showa Zone of Oromia region, Ethiopia. The experiment was laid out in Randomized Complete Block Design (RCBD) in three replication and contains five (four fungicide and one control) treatments. All the fungicides were applied at the first day of strip rust disease symptom appearance and repeated at 14 th day interval. Disease parameters like incidence, severity, Area under Disease Progress curve (AUDPC), and yield loss (Dry biomass, grain yield and thousand grain weight) were used to evaluate the treatments. The fungicides showed significant differences (P<0.05) in reducing incidence, severity, AUDPC and yield losses compared to the control treatment. There also significant differences between Zantara EC 216 and Rex®Duo fungicide in reducing disease incidence. also between Zantara EC 216 and Tilt 250 EC in reducing the disease severity. The strip rust severity from the control plot was 76.66 which was reduced to 4.44, 10.99, 14.33 and 21.11 % by Zantara EC 216, Rex®Duo, Tilt 250 EC and Progress fungicide, respectively. Zantara EC 216 fungicide reduced strip rust severity by 94.2% compared to the control treatment. The analysis of variance also revealed significant difference among Zantara EC 216 and Rex®Duo, Tilt 250 EC and Progress fungicides in reducing grain yield loss and thousand grain weights loss. Zantara EC 216 fungicide increased grain yield by 32.2% compared to the control. However, in most parameters, there was no significant difference among Rex®Duo, Tilt 250 EC and Progress fungicides. Hence, Zantara EC 216 EC 216 which is newly introduced to Ethiopian country was very effective and can be recommended as alternative fungicide for the management of strip rust of wheat.


INTRODUCTION
Wheat is one of the most important cereal crop produced worldwide (Curtis et al., 2002) and thought that it is the first crop ever to be cultivated and playing a major role in human's economic and social development worldwide (Thabet and Najeeb 2017). It is the major cereal crop which playing a significant role in feeding a hungry world and improving global food security (Ketema and Kassa 2016).
Wheat is produced across a wide range of agro-ecological and crop management regime (Belay and Tanners 1999). The most suitable area for wheat production falls between 1900-2700 m.a.s.l (Hailu et al. 1991). In 2017, the area under production by wheat worldwide and the yield obtained was 218.54 million hectares and 771.72 million metric tons, respectively, (FAOSTA 2019). Wheat is the staple food for about 4.5 billion people in the world (Braun et al. 2010).
In Ethiopia, wheat ranks fourth in area coverage and importance next to teff (Eragrostis teff Zucc.), maize (Zea mays L.) and sorghum (Sorghum bicolor L.) (CSA 2015). Ethiopia is the second largest wheat producer next to South Africa in sub Saharan Africa countries (FAO 2015b) and west and southwest Shewa zones are among the major wheat producing areas in Oromia region (CSA 2014). Although the productivity of wheat has increased in the last few years in Ethiopia, it is still very low as compared to other wheat producing countries. The national average productivity is estimated to be 2.5 tons/ha (Samuel Gebreselassie et al. 2017), which is by far below the world's average of 3.3 tons/ha (FAO 2007).
Productivity of wheat in Sub Saharan Africa is challenged by a number of abiotic and biotic stresses like drought, soil acidity, erosion, poor soil fertility, diseases, insects and weeds (Wuletaw Tadesse et al. 2018) of which rust diseases are the most destructive factors because of their ability to move long distance and form new virulent races causing serous loses (Huerta-Espino et al. 2011). Rusts diseases causes up to 60 and 100 % loss of wheat yield by leaf or stripe (yellow) rust and stem rust, respectively, (Park et al. 2007). In spite of great progress made in their control in many countries, it is considered the major diseases of wheat since no other wheat disease could result in greater loss over large area in a given year (Stakman et al. 1962). Wheat stripe rust, caused by Puccinia striiformis is one of the most widespread and destructive diseases of the crop worldwide (Chai et al., 2015). The disease was first reported in the early of 1940's in Ethiopia and since then it is becoming more devastating and wide spread following the spread of semi-dwarf improved wheat cultivars (Hailuet al. 1991). Stripe rust disease became endemic in Ethiopia since 2010 and caused huge losses to Ethiopian farmers (ICARDA 2013). The disease favored by minimum temperature, relative humidity and rainfall, while its development reduced with maximum temperature (Salman et al. 2006). In severe cases up to 100% yield loss was recorded due to strip rust in highly susceptible varieties (CIMMYT 2010).
Even though widespread deployment and cultivation of resistant cultivars (Loughman et al. 2005), in Ethiopia, the current commercial wheat cultivars are not withstanding the effect of the pathogen and it is not possible to grow a profitable wheat crop without the application of fungicides (Wanyera 2009). Foliar fungicide spraying has increased due to the breakdown of resistance to rust in wheat in several countries (Murray and Brennan 2009;Kang, et al. 2010). In Ethiopia, large-scale wheat growers in Arsi and Bale regions have extensively used fungicides to control rusts, spending around 0.5 million US dollars on chemicals annually (CIMMYT 2005). Generally, rust control by fungicide application is one of the most popular means of maximizing grain yield globally. Fungicides can also play a role in an integrated management of the disease until new cultivars with genetic resistance are available (Loughman et al. 2005). However, until recently farmers in Ethiopia did not use fungicides in wheat production due to lack of awareness about the yield advantage gained by fungicide application, availability and cost of fungicides. Therefore, the objective of this study was to assess the effectivity of different fungicides including the newly introduced product (Zantara EC 216 EC 216) to control strip rust of wheat at west showa zone of Oromia region on susceptible variety.

Study area:
The study was conducted at west showa zone Toke kutaye district under rain fed conditions during 2010/11 main cropping seasons of Ethiopia. The area represents the major wheat growing areas in the zone and hot spot locations for strip rust. The coordinate of the site is 8 0 58'13.56"N 37 0 45'39.83"E with altitude of 2129 masl. The minimum and maximum temperature of the district ranges from 10.2-11.7 and 21.8-24.4 O C, respectively, with a mean annual rain fall which ranges from 125-218mm. The main rainy season of the site was from June to September when it receives 70% of the annual rainfall.

Treatments and experimental design
Bread wheat Digalu variety which is highly susceptible to yellow rust (Puccinia striiformis f.sp. tritici) diseases and popular in the area was planted at yellow rust hot spot location of west showa zone, on plot size of 5 m x 5 m. The spacing between the plots and replication was 1m and 1.5m, respectively. The recommended rates of 41 kg/ ha N and 46 kg/ha P2O5 fertilizer were applied during planting. Four fungicides (Tilt 250 EC, Progress, Rex®Duo and the new product Zantara EC 216 fungicides) and control (fungicide unsprayed check) were used as treatments. All the fungicides were applied as per the recommendation rate and schedule of the manufacturer. Hand weeding was practiced twice to control weed in the experimental field. All the other agricultural practices were undertaken as recommended.

Disease assessment
Following the appearance of the symptom (strip rust), fungicide treatment was applied and repeated at 14 th day interval. Strip rust disease incidence and severity percentage was started to be assessed at fourth days of the first fungicide application from 10 randomly selected and pre-tagged tillers of each plots continued at weekly interval. Wheat strip rust incidence was measured as the proportion of the number of leaves showing strip rust of the total leaves assessed as: Strip rust severity was scored in percentage using the modified Cobb's Scale (Peterson et al., 1948). From the severity data, AUDPC for each treatment was calculated as described by Campbell and Madden (1990). As follows, Where, xi is the percentage of disease severity index at i th assessment; ti is the time of the i th assessment in days from the first assessment date; and n is the total number of days disease severity was assessed.

Relative Yield loss (%)
Potential reduction of grain yield loss (in the absence of foliar spray of fungicides) was calculated as yield difference between fungicides sprayed and control treatment expressed in percentage of the sprayed plots (Sharma et al. 2016) as follows: (S ) Where, RYL= relative yield loss in percent, Yfs= yield from the fungicide sprayed plots and Yfuns= yield from fungicide unsprayed.

Losses in thousand seed weight
Losses in thousand seed weight was calculated in the same way as FAO (1971).

Fungicide Efficacy
The fungicide efficacy (FE) was calculated using Abbott's formula (Abbott 1925) as,

cy (
Where, X -Disease severity in control, Y -Disease severity in treated plots.

RESULT AND DISCUSSION
In the cropping season, of 2018, the occurrence of strip rust disease was slightly sever and the treatments showed differences in reducing the disease on the wheat crop. The fungicides reduced the disease significantly (P< 0.05) over unsprayed plot.

Effect of Fungicides on Strip Rust of Wheat Incidence and Severity
The analysis of the result revealed that, the fungicides significantly (P<0.05) reduced the incidence of strip rust disease of wheat as compared to the plot not sprayed with fungicide. The analysis of the variance showed that there was significantly (P< 0.05) difference among treatments in reducing wheat strip rust severity. The disease severity of strip rust on the control plot was 76.66% which was reduced to 4.44, 10.99, 14.33, 21.11% by Zantara EC 216, Rex®Duo, Progress and Tilt 250 EC fungicides, respectively, (Table 3.1). However, there was no significance differences in reducing strip rust severity disease among Zantara EC 216, Rex®Duo and Progress fungicides. Theses fungicides (Zantara EC 216, Rex®Duo and Progress) reduced strip rust severity disease by 94.21, 85.66 and 81.31%, respectively, compared to the control treatment. These fungicides showed comparable reduction of strip rust severity. The disease severity recorded from fungicide unsprayed treatment in this study was in line with the study conducted by Ayalew et al.  The analysis result showed significant differences due to treatments in area under disease progress curve (AUDPC) of strip rust disease of wheat crops. The AUDPC the control plot was 672% which was reduced to 86, 104, 118 and 143% by Zantara EC 216, Rex®Duo, Progress and Tilt 250 EC fungicides, respectively (Fig 3.1). Zantara EC 216 and Rex®Duo fungicides reduced the AUDPC of wheat strip rust by 586 and 568 over the control treatment. Which was 87.2 and 84.5 % compared to the control treatment. Even though there was no significance difference among fungicides in reducing the AUDPC, Zantara EC 216 fungicide reduced AUDPC by 39.86, 27.11 and 17.30% as compared to Tilt 250 EC, Progress and Rex®Duo fungicides, respectively. Yared Tesfaye et al. (2018) also reported significant differences due to fungicide treatments on AUDPC. The authors also reported that non-significant difference in AUDPC between Tilt 250 EC and Rex®Duo fungicides which was in line with this study. Viljanen-Rollinson et al. (2002) reported that application azoxystrobin and epoxiconazole on strip rust of wheat reduced the AUDPC of the disease by 65% and 37%, respectively. Fungicides like Amista Xtra 280 SC, Orius 25 EW, Folicur 250 EC, and Silvacur 375 EC also reported to reduced the AUDPC of strip rust of wheat (Wanyera et al. 2014)

Effect of fungicides on Biomass and Grain yield of wheat
The analysis of variance indicated that there was a significant (p < 0.05) difference among treatments in affecting wheat biomass yield and grain yield reduction due to strip rust disease. The biomass of the wheat crop from fungicide unsprayed plot was 9222.2 kg/ha (92.22q/ha) which was increased to 11777.8 kg/ha (117.77q/ha), 10814.8 (108.15q/ha), 10148.1 (101.48 q/ha) and 9740.7 (97.41q/ha) when treated by Zantara EC 216, Rex®Duo, Progress and Tilt 250 EC fungicides, respectively, (Table 3.2). However, there were no significant differences among Rex Dou, Progress, Tilt 250 EC and the control treatments in increasing the biomass of wheat crop. Wubishet Alemu and Tamene Mideksa (2016) also reported non-significant effect on biomass of wheat when treated with fungicides to manage rust disease. There was 2555.5 kg/ha (25.56 q/ha) biomass yield advantage by treating wheat infected by strip rust Zantara EC 216 EC 216 fungicide compared to fungicide unsprayed plot. Even though there was no significant difference between Zantara EC 216 and Rex®Duo, Zantara EC 216 provide 963.0 kg/ha (9.63q/ha) biomass yield advantage over Rex®Duo fungicide. Sebei Abdennour et al. (2018) also reported significances differences in biomass of wheat crop infected by strip rust compared to untreated control after treated by fungicides when the disease pressure is high.
The result of the analysis revealed that significant (p< 0.05) difference among treatments in reducing yield losses due to strip rust of wheat (Table 3.2). The grain yield obtained from the plots treated by the Zantara EC 216, Rex®Duo and Tilt 250 EC fungicides were 4370.4 kg/ha (43.7 q/ha), 3703.7kg/ha (37.4 q/ha) and 3555.6 (35.56q/ha), respectively, which was reduced to 2962.9 kg/ha (29.6 q/ha) from the plot fungicide unsprayed plot (Table 3.2). Zantara EC 216 and Rex®Duo fungicides provided significant yield advantage over the control treatments. However there was no significant difference in reducing yield loss among Rex®Duo, Tilt 250 EC and Progress treatments. Even though there was no significant difference among Tilt 250 EC, Progress and the control treatments statistically, Tilt 250 EC and Progress treatments provided 5.93 and 5.19 q/ha yield advantage over the control treatments. All the fungicides revealed significant better yield advantage over the control treatment The yield obtained by Rex®Duo fungicide (37.4 q/ha) in this study was in line with the yield obtained by the same fungicide in the study conducted by Yared Tesfaye et al.(2018) at Yirba site of Bore research center which was 38.8 q/ha. There was 14.8q/ha grain yield advantage from plots treated by Zantara EC 216 fungicide over the control treatment which was 32.21% yield increment. This result was in agreement with the study conducted by Sharma et al. (2016) on reduction of wheat yield losses caused by stripe rust, in which up to 39 % yield increment was obtained by different fungicides compared to unsprayed plot. Singh et al. (2016) also reported 44.29 % yield increment of grain yield when treated with fungicide as compared to untreated plot In this study the yield increments due to fungicide application on wheat infected by strip rust was slightly lower compared to the previous report using fungicides. This lower yield increment could be due to the low infestation level by the disease during the season.

Effect of fungicide on thousand grain weight of wheat infected by strip rust disease
There was a significant difference among treatments in reducing thousand grain weight loss of wheat crop infected by strip rusts. Zantara EC 216 fungicide revealed the highest mean (44.03gm) thousand grain weights compared whereas the smallest (38.0gm) was recorded from control treatment. However, there was no significant difference among Tilt 250 EC, Rex®Duo and Progress treatments on thousand grain weights (table  3.2). Wubishet Alemu and Tamene Mideksa (2016) also reported non-significant difference among different fungicides on thousand grain weight of wheat infected by rust disease. Zantara EC 216 fungicide increased thousand grain weight of wheat infected by strip rust by 9.6 and 7.7% compared to the control and Progress fungicide, respectively. The study conducted by Yared Tesfaye et al.(2018) reported 60gm of thousand grain weight by using Rex®Duo and also Tilt 250 EC fungicide as control measure against strip rust at Guji Zone Southern Ethiopia, which is much larger than the weight obtained in this study by the same fungicide. This less weight could be, during the flowering and seed filling period the rain fall of the season was minimum and erratic. This could be probable the possible reason for lower thousand grain weight.

CONCLUSION
Application of fungicides to strip rust (Puccinia striiformis) diseased wheat crop has significant effect. The evaluation of fungicides indicated that all the fungicides control the strip rust/yellow rust (Puccinia striiformis) of wheat better than the control treatment. Moreover, the newly introduced fungicide (Zantara EC 216) for the control of strip rust of wheat was by far better than all the fungicides used in this experiment for the control of