Parthenium Weed (Parthenium hysterophorus L.) Research in Ethiopia: Impacts on Food Production, Plant Biodiversity and Human Health

The highly competitive, adaptable and allergenic weed Parthenium hysterophorus (Compositae) is an invasive annual weed believed to be introduced to Ethiopia in 1970s. Field surveys, plant biodiversity impacts, and analysis of secondary plant compounds in P. hysterophorus and its possible impact on human health have been studied in Ethiopia since 1998. The weed has invaded a variety of habitats ranging from roadsides to grasslands and crop fields. Infestations were found to be greater than 20 plants per m2 and yield losses in sorghum reached 46-97% depending on the location and year. In grasslands dominated by parthenium, native plant species composition and abundance was found to be low. Manual control of parthenium by farmers resulted in the development of skin allergies, itching, fever, and asthma. These reactions could be attributed to the presence of secondary plant compounds (parthenin, chlorogenic acid, isocholorogenic acid, vanilic acid and caffeic acid) which were found in parthenium with significant variation in their concentrations among the different plant parts, dependent on plant locality, moisture content and plant size. The social cost of parthenium in Ethiopia was measured by Disability Adjusted Life Years and its equivalence in terms of monetary value was estimated at US$ 2,535,887 - 4,365,057. More resources have to be invested to tackle the parthenium problem as the estimated loss is disproportionate to the cost of investment in parthenium research and development activities

Adaptability of two weevils (Neochetina bruchi and Neochetina eichhorniae) with potential to control water hyacinth in the Rift Valley of Ethiopia

Neochetina weevils have potential as biocontrol agents for water hyacinth, an aquatic weed which seriously affects irrigation water supply in sugarcane, vegetables and other horticultural crop production in the Rift Valley of Ethiopia. A study was conducted on (i) the adaptability and duration of developmental stages of Neochetina weevils and (ii) the damage they cause to water hyacinth in the Rift Valley of Ethiopia. The Rift Valley weather conditions appeared to be suitable for the two weevil species studied, enabling them to produce four generations per year. The egg hatching period of Neochetina bruchi ranged from 4 to 10 days, while Neochetinaeichhorniae took 8–12 days. Larvae of N. bruchi took a comparatively shorter period (32–38 days) than N. eichhorniae (52–60 days) to complete their development. N. bruchi laid a maximum of 10.4 eggs female-1 day-1, whereas N. eichhorniae laid 8.2 eggs female-1 day-1. The intrinsic rate of increase of N. bruchi was found to be 0.06 with a generation time of 74.8 days and a population doubling period of 14.3 days. The intrinsic rate of increase of N. eichhorniae was 0.046 accompanied by a generation time of 94.8 days and a doubling period of 18.7 days. Feeding by adult weevils and tunnelling by larvae significantly impacted the vigour and reproduction of water hyacinth plants. N. bruchi and N. eichhorniae affected plants had about 72% (76%) and 66% (58%) reduction in fresh (and dry) weight, respectively. Thus, based on their damage potential and difference in rate of population growth, it is concluded that N. bruchi could be considered as a promising candidate for biological control of water hyacinth under Ethiopian conditions

Water Hyacinth in the Rift Valley Water Bodies of Ethiopia: Its Distribution, Socioeconomic Importance and Management

A survey was conducted in the Rift Valley water bodies of Ethiopia from 2009 to 2011 to (i) determine the prevalence, agro-ecological distribution and sources of infestation of water hyacinth, (ii) investigate the socio-economic impact of water hyacinth, and (iii) assess changes in its agro-ecological distribution. Water hyacinth was first introduced into the Rift Valley water bodies as an ornamental plant in the 1950s around the Aba-Samuel Dam. Eventually, it spread into Lake Koka, Lake Ellen, Koka Dam and Wonji site via the Awash River. Now it is common in various water bodies located at low, mid and high altitudes. At Lake Koka, Lake Ellen, Aba-Samuel Dam and Koka Dam, an increase in water cover was observed during the study period. Univariate as well as PCA analysis indicated that rainfall, intensity of wave action on the water bodies, water depth, N and P content of the water bodies were the factors representing the majority of correlations with water hyacinth coverage. Interviews revealed that the weed mats had an adverse socioeconomic impact on the local communities and enterprises. The present assessment also noted that no major management strategy had been employed in the infested water bodies except at Wonji and Koka Dam where a significant reduction (i.e., <7% distribution) has been achieved. On the contrary, increasing trend of water hyacinth invasion had been observed in the upstream water bodies. Hence, effective management strategy should be implemented in the upstream water bodies so as sustain achievements in Wonji