Weed Species Diversity, Distribution and Infestation Trend in Small Scale Irrigated Vegetable Production Area of Mid-Rift-Valley of Ethiopia

Abstract

The gradual worsening of crop pests in mid rift valley of Ethiopia is among the major bottlenecks of vegetable production and productivity. This study was to reveal the contribution of weeds in complicating the pest control in irrigated vegetable production area of Ethiopian. The study was carried out in five districts of East Shewa Zone of mid-Rift valley of Ethiopia (Adami Tulu, Dugda, Liben Chukala, Bora and Lume) known by their high potential irrigated vegetable cultivation. A quadrate sampling and group and individual discussions were used as a tool of data collection. Abundance (A), Dominancy (D), Frequency (F) and Importance Value (IV) and their corresponding Relative value of the species were calculated from the species count and cover data collected. The assessment result showed that 27 weed families comprised 78 weed species were identified. Asteraceae, Poaceae, Amarantaceae, Chenopodaceae and Solonaceae were found the 1st, 2nd, 3rd and 5th important weed families comprising a total of 17, 14, 5, 5 and 4 species respectively. Information obtained from farmer’s interview noted that some weeds which scored low importance value (IV) were found important in influencing the livelihood of the community in one way or another. Amaranthus spinosus, Tribulus cistoides, Euphorbia schimperian, Sorghum arundinacium, Acanthospermum hispidum, Amaranthus hybridus, Parthenium hysterophorus, Snowdenia polystachya and Xanthium spinosum were categorized as weeds known by poisoning livestock in the area. Foeniculum vulgare, Orobanche minor, Parthenium hysterophorus and Portulaca oleracea were categorized among weeds difficult to control using herbicide. Portulaca oleracea, Argemone mexicana, Orobanche minor, Chenopodium murale, Verbesina encelioides, Parthenium hysterophorus, Flaveria trinervia and Launaeaintybacea were listed among weed species currently highly invading the area. Nicandra physaloides, Xanthium strumarium, Parthenium hysterophorus, Datura stramonium and Erucastrumabyssinicum were marked as weeds serving as alternate host for either insects or disease of vegetables. Limited use of crop rotation and herbicide in vegetable fields, unavailability of species specific herbicides, poor field sanitation and fragmented landholding system of the area as a whole were observed as a driving force for the ever expansion of weed invasion in the area.