Original Research Article

Year: 2017 | Month: Jan.-March | Volume: 1 | Issue: 1 | Pages: 21-25

Survey and Identification of Diseases on Major Crops of Assosa and Kamashi Zones, Ethiopia

Minyahil Kebede, Assefa Gidesa

Ethiopian Institute of Agricultural Research; Assosa Agricultural Research Centre, Assosa, Ethiopia.

Corresponding Author: Assefa Gidesa

ABSTRACT

A survey was conducted in major crops of Assosa and Kamashi zones of Benishangul Gumuz Regional State during 2015 cropping season with an aim of identifying problematic diseases and providing baseline information on diseases of major crops in the study area. Disease assessments of major crops in both zones (except for Maize and Sorghum fields) were conducted by using 1m x 1m quadrate laid along diagonal of the fields. While, in Sorghum and Maize fields five plants per spot were randomly chosen along diagonal of the field for inspection. Moreover, plants with in the quadrants and/or the chosen plants per spots were thoroughly examined from base to the apex for diseases incidence and severity. A total of 63 farmers field were enclosed by this survey. It was founded that about 22 diseases of major crops of the study area were recorded from the field crops of the area. The result of this survey showed, major diseases of major field crops of Assosa and Kamashi zones in order of their importance were: 1) Colletotrichum sublineolum of Sorghum, 2) Xanthomonas campestris pv. sesami of Sesame, 3) Mycosphaerella graminicola of Soybean, 4) Brown spot of Finger millet, 5) Exserohilum turcicum of Maize, 6) Maize Streak Virus of Maize, 7) Cercospora sorghi of Sorghum, 8) Magnaporthe grisea of Finger millet and 9) Fusarium wilt of Hot pepper; respectively each with a magnitude of percentage disease severity index of 46.3, 42.58, 38.27, 38.10, 37.78, 37.33, 35.53, 34.13 and 31.48. Therefore, any intervention including direct research toward creating new or adopting an integrated disease management options must focus on those prioritized major diseases of the area; to have higher, good and quality agricultural produces. In addition, regular disease survey and/or surveillance must be conducted to identify possible challenging diseases of major field crops in the study area.

Key words:Diseases, major crops, disease severity, disease incidence and disease severity index.

INTRODUCTION

One of the most common problems encountered by farmers throughout the world is a control of pests that interfaces with agricultural production. It causes a serious damage to crops by effectively competing with the beneficial and desired crop, damaging plant and plant parts and by other chemical effects. In addition, the pest increases labor that adds to the cost of production, and reduces yields of crops.
In case of Benishangul Gumuz Regional State, agriculture accounts for 93.2% of the regional economy ^[3] and also the region was one of the potential regions of the country endowed with fertile land and ample rainfall, which are suitable for agricultural production. ^[2] The major crops grown in the region including currently emerging crops are: sorghum, maize, finger millet, sesame, Niger seed, groundnut, soybean, hot pepper, and mango. ^[1,5] Even though the region is suitable, but there were so many obstacles for the agricultural sector of the region. Among them, crop diseases and pests are serious problems that contributed to low crop productivity. ^[2] For instance, Dutch Interchurch Aid ^[4] reported that in Assosa district pests caused a total of annual crop loss was estimated to 30-40%.
Yet, there was no research based information on the lists of constraining diseases pests of major crops of Assosa and Kamashi zones of Benishangul Gumuz region. Taking this in to consideration, the crop protection team of AsARC was initiated this survey study with the aim of identifying problematic diseases and providing baseline information on the diseases of major crops in the study area. Furthermore, it was also aimed to make the information available for any individuals or an organization who was interested for diseases of major crops in Assosa and Kamashi zones of Benishangul Gumuz region for further works.

MATERIALS AND METHODS
The survey was conducted at Assosa zone (in Assosa, Bambasi, and Homosha districts or 'Woredas') and Kamashi zone (in Kamashi district) of Benishangul Gumuz region. In each district crops of major importance were selected and attention was given to those selected crops of the area at the time of implementing the survey. This survey was assessed thoroughly in a total of 63 farmer fields in 2015 main cropping season. Within selected fields a quadrant of 1m x 1m was thrown and disease incidence and severity were taken for every quadrant by crossing the fields diagonally. All plants within the quadrant were thoroughly observed starting from the ground up to the tip shoots of the crop and the severity of existing diseases was rated by using 1-9 disease scoring scales. Besides, for fields that were not easy to use 1m * 1m quadrants (e.g., in Maize and Sorghum fields), five plants per spot were taken and disease assessment was made on them by following the same procedures as the previous one. Also, altitude and GPS coordinates of each crop field were collected. Moreover, disease incidence and severity was calculated by using the following equations (eqn. 1 to 3):

Equation 1

Equation 2

Equation 3

Where; is number of assessed plants, b is severity scale scored, N is total number of assessed plants, and K is the highest severity score scale.

RESULTS AND DISCUSSIONS

The major field crops of Assosa zone were Sorghum, Maize, Soybean, Niger seed, Finger millet, Ground nut and Hot pepper, while that of Kamashi zone were also Sorghum, Maize and Sesame. Therefore, this survey was focused on these major crops of the study area. The result of this assessment founded that, twenty two diseases were recorded on major crops of Assosa and Kamashi zones of Benishangul Gumuz region (see table 1). Among them, E. turcicum (Leaf blight), Maize Streak Virus, C. sorghi (Grey leaf spot) and Maize Stripe Virus diseases of maize crops, Cercospora leaf spot disease of Niger seed, Hot pepper and Sesame, and X. campestris pv. sesami (Bacterial blight) disease of Sesame were found in all assessed fields of the study area with a disease incidence of 100 percent. Next to these, the highest disease incidence (90%) was recorded by C. personatum (Late leaf spot) disease of Groundnut. On the other side, the lowest disease severity was recorded on sorghum diseases namely, S. sorghi (Covered kernel smut) and R. sorghicola (Oval leaf spot)respectively,with 6.25 and 18.75 percent of incidence (table 1).
Moreover as illustrated in table 2, the most important major field crop diseases of Assosa and Kamashi zones that need management intervention in their descending order were C. sublineolum (Anthracnose) of Sorghum, X. campestris pv. sesami (Bacterial blight) of Sesame, M. graminicola (Leaf blotch) of Soybean, Brown spot of Finger millet, E. turcicum (Leaf blight) of Maize, Maize streak virus of Maize, C. sorghi (Grey leaf spot) of Sorghum, M. grisea (Blast) of Finger millet and Fusarium wilt of Hot pepper. The disease severity indexes of the most important diseases of major crops of the study area was respectively, 46.30%, 42.58%, 38.27%, 38.10%, 37.78%, 37.33%, 35.53%, 34.13%, and 31.48%.
Sorghum Diseases of Assosa and Kamashi Zones
Among the five diseases recorded on sorghum crops (as shown in table 2), the incidence of C. sublineolum in Assosa and Bambasi districts of Assosa zone were 100%, while in Kamashi distric of Kamashi zone the incidence was 75%. Also, C. sublineolum was 50% incidence in Homosha district of Assosa zone. Thiese implies, C. sublineolum of sorghum diseases was geographically distributed in all sorghum growing areas of Assosa, and Bambasi districts. However, in Kamashi and Homosha districts C. sublineolum was covered 75% and 50% of sorghum growing areas, respectively. On the other hand, C. sublineolum was commonly observed in sorghum fields of Assosa and Bambasi districts, i.e. it was a major disease of sorghum in thess areas. In the same way, the highest severity (5 and 5.14) of C. sublineolum was recorded on sorghum fields of Assosa and Bambasi districts In the case of Homosha and Kamashi, the severity of C. sublineolum was 3 and 2.5, respectively; whichopposes the incidence.

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