«Eragrostis tef(Zucc.) Trotter Seyfu Ketema Biodiversity Institute Addis Abeba, Ethiopia 2 Tef. Eragrostis tef (Zucc.) Trotter The International Plant ...»
Weed competition causes about 52% crop losses, but with hand-weeding (even at the wrong time), crop loss is 8% (Berhanu 1986). Pre-sowing and post-emergence herbicides available for the control of weeds in tef are indicated in Table 10.
Table 10. Recommended rates of herbicides and their time of application (Berhanu 1986)
Berhanu (1986) has stated that the pre-sowing herbicides should be applied 1weeks before planting while the post-emergence herbicides should be applied at early tillering (4-5 weeks after sowing). The pre-sowing herbicides have shown an acceptable control level for annual broadleaf and grass weeds, though they did not satisfactorily control the perennial weed species. All the post-emergence herbicides listed in Table 10 had good control for only the broadleaf weeds and not for the grasses and sedges.
39 Promoting the conservation and use of underutilized and neglected crops. 12.
Diseases Diseases are not a serious problem. In the major tef-growing areas of Ethiopia tef suffers less from diseases than most other cereal crops in the major production areas of Ethiopia (Stewart and Dagnachew 1967).
Tef rust (Uromyces eragrustidis Tracy) and head smudge (Helminthosporium miyakei Nisikado) have been reported as the most important diseases on tef (Stewart and Dagnachew 1967; Tareke 1981). According to Tadesse (1969, citing Castellani et al.
1939), rust causes an average loss of l0-25%.
Damping-off caused by Drechslera poae (Baudis) Shoemaker has been found to be severe and even damaging when higher rather than lower seed rates and early rather than late sowing dates were practised.
Spraying tridemorph has decreased helminthosporium leafspot (Helminthosporium spp.) from a 25-30% infection level to a l-2% level.
Insect pests The control methods of the most important insect pests of tef are presented below.
Welo bush-cricket (Decticoides brevipennis Ragge), locally known as degeza, is new to science; it is a major pest existing only in Ethiopia with its distribution being recorded in the altitude range of 1550-2516 m in Tigrai, Welo, Gonder, Gojam and Shewa, but not in Welega (Stretch et al. 1980). As the early instars of D. brevipennis are flower feeders, slashing of weeds in the field margins before cereals have headed would deprive this pest of food and reduce its population near crops. Early sowing of cereal crops would also enable them to mature before the natural food sources of this potential pest dry completely As D. brevipennis has only one generation a year, one well-timed application of insecticide can almost eliminate it from an area, especially since migration is minimal (Stretch et al. 1980). The application of 8kg/ha of 2.6% BHC as dust has been found effective in controlling Welo bush cricket.
For control of central shootfly (Hylemya arambourgi) a seed dressing before sowing with 40% Aldrin WP at the rate of 50 g/kg of seed is recommended.
Red tef worm (Mentaxya ignicollis Walker) was first reported as a pest of tef in 1970 south and west of Addis Abeba on black clay soils. Since then, losses from red tef worm were estimated to be l0-30% in five regions of Ethiopia. Repeated crop losses have been observed in Becho area of Shewa. Preliminary study results indicate that Digitaria scalarum and Phalaris spp. were the important alternate wild hosts of red tef worm. Some of the insecticides found useful to control red tef worm are (Tadesse, 1996, pers. comm.): Cypermethrin, 25% e.c. (187.5 g a.i./ha, 750 ml/ha) or Fenitrothion, 50% e.c. (625.0 g a.i./ha, 1.25 ml/ha). Spraying should be done when, on the average; 25 larvae/m2 of red tef worm are counted.
the plant gets too dry helps prevent losses from shattering. It is threshed by trampling the harvested crop either with oxen or by using threshers. The grain is stored outside the house in a granary made of wood or bamboo plastered with mud mixed with tef straw to reinforce it, or stored in the house using other storage containers. Tef seed is stored very easily for several years under local storage conditions because it is not attacked by weevils or other storage pests and chemicals are not required to control storage pests. Tef straw is nutritious feed. It is piled up and stored outside the house after threshing for animal feed.
41 Promoting the conservation and use of underutilized and neglected crops. 12.
11 Limitations of the crop The small size of tef seed poses problems during sowing, and indirectly during weeding and threshing. At sowing the very small seed size makes it difficult to control population density and its distribution. This remains true whether one broadcasts the seed by hand, uses a broadcaster or a seed driller.
The uneven plant stand after germination has an impact on nutrient use efficiency of the crop and crop yield. Owing to the scattered plant stand, farmers find it difficult to use mechanical weeding implements and are forced to either hand-weed or use chemical herbicides.
Threshers or combine harvesters are used to thresh tef. However, seed loss is incurred because tef seed is very small and light and gets blown away with the chaff.
Harvesting of the crop is difficult because of lodging. Since tef lodges heavily it is not advisable to use higher rates of fertilizer to increase yield. The current landraces and cultivars used are not lodging resistant and the development of genetically lodging-resistant cultivars is essential.
Landraces and current cultivars give low yield. At present the national average grain yield of tef is 910 kg/ha. Improved varieties of tef give a grain yield of 1700kg/ha on farmers’ fields and 2200-2800 kg/ha under research-managed large farms. However, no comprehensive study has been conducted to assess the yield potential of the crop.
The study of 2255 accessions of tef has demonstrated the high yield potential of the crop (Seyfu 1993). Thus, it is not fair at this point to state that low yield is one of the genetic limitations of the crop. The personal opinion of the author is that the crop has great potential for improvement and could give more than 6 t/ha if it receives adequate research attention. Low grain yield, and production constraints such as lodging, drought, waterlogging, heat and frost might be overcome through a comprehensive plant breeding programme since there exists genetic variation in tef germplasm for these traits. In addition to using the existing genetic variation to overcome some of the production constraints, development of improved and appropriate agronomic practices (seed rate, sowing dates, seedbed preparation, fertilizer type, rate and time of application) and cropping systems (crop sequence, relay cropping, intercropping, etc.) would greatly contribute to overcoming production constraints and improving, the productivity of the crop.
42 Tef. Eragrostis tef (Zucc.) Trotter 12 Prospects and research needs Ethiopian farmers prefer to grow tef because of the following advantages (Seyfu 1991):
It can be grown in areas experiencing moisture stress.
It can be grown in waterlogged areas and withstands anaerobic conditions better than many other cereals including maize, wheat and sorghum.
It is suitable for use in multiple-cropping systems such as double, relay and intercropping.
Its straw is a valuable feed during the dry season when there is an acute shortage.
It is highly preferred by cattle over the straw of other cereals and demands high prices in the markets.
It has acceptance in the national diet, has high demand and high market value and hence enables farmers to earn more than with other crops.
It is a reliable and low-risk crop.
In moisture-stress areas, farmers use it as a rescue crop. For example, around Kobo and Zeway, which are areas with low and erratic rainfall, farmers first plant maize around April. If this fails after a month or more because of moisture stress or pest problems they plough it under and plant sorghum. If this also fails after a month or more then they sow tef as a last resort, which often survives on the remaining moisture in the soil and yields some grain for human consumption and straw for feed.
It is not attacked by weevils and other storage pests and therefore is easily and safely stored under local storage conditions. This results in reduced post-harvest management costs.
Compared with any other cereals growing in Ethiopia it has fewer disease and pest problems (Stewart and Dagnachew 1967).
It was stated earlier that the ability of tef to tolerate and grow under waterlogged conditions is one of its advantages and a characteristic that makes it preferred by farmers. Experimental results have shown that under undrained conditions without fertilization, tef gave a 106% grain yield advantage over wheat and 70% under undrained conditions with fertilization (Hiruy 1986). This indicates that tef is relatively more tolerant to waterlogged conditions than wheat.
The other advantage of tef for farmers is its suitability for easy storage under local storage conditions (using goteras), without incurring much loss; this has been substantiated by various study results.
Results of experiments conducted in Ethiopia under natural environmental conditions and traditional storage systems indicate that tef does not incur any loss as a result of damage by any storage insect pests (Yemane and Yilma 1989).
Currently diseases are not a serious problem in tef in the major tef-growing areas of Ethiopia. Tef suffers less from diseases than most other cereal crops in the major production areas of Ethiopia (Stewart and Dagnachew 1967).
Jansen et al. (1962) reported that tef has an excellent balance among the essential amino acids that makes it comparable to that of egg, except for its somewhat low 43 Promoting the conservation and use of underutilized and neglected crops. 12.
lysine content, which can be supplemented by the use of fenugreek, pulses and soyabean, which can be locally grown.
The characterization work done by Seyfu (1993) has shown that among the 2255 pure line accessions there is a high variability for grain yield per plant, straw yield per plant and harvest index. The potential has been shown for the development, through direct selection as well as gene recombination, of cultivars that are either mainly forage or dual-purpose types with acceptable levels of both grain and straw yield.
Tef has its own unique qualities and advantages, and thus its introduction to other parts of the world could be of benefit to many nations. Its benefit as a forage crop to South Africa has been described by Burt-Davy (1913).
The crop has a wealth of genetic diversity which could be utilized to overcome present constraints through proper germplasm conservation and utilization efforts.
The gaps in current germplasm collections and suggestions made for future action, both of which were indicated earlier, need to be addressed in order to utilize the germplasm and overcome present constraints. Targeted collecting of germplasm from stress areas such as waterlogged areas, low-temperature and drought-prone areas, etc. would be useful. Development of rapid and cheap screening techniques to identify various stress-tolerant cultivars and identify and utilize efficient breeding or biotechnology techniques for developing superior cultivars are essential for overcoming present constraints.
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