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An attempt was made to optimize the minimum required inoculation load of the weevils on three growth stages of waterhyacinth, based on reduction of fresh biomass, number of leaves and ramifications. The small growth stage was controlled earlier than the waterhyacinth of middle growth stage, corresponding to the increase in number of weevils per plant. The large plants could not be controlled even with the inoculation pressure of 20 weevils per plant because of high growth rate. This study suggests that Neochetina spp. has the potential to keep the population of the macrophyte at a subeconomic density, through a basic inoculation load of weevils in due course of time.
Life cannot exist without water. Appropriate management of water, from the water’s source to its utilization, is necessary to sustain life. Aquatic weeds pose a serious threat to aquatic environments and related eco-environments. Short- and long-term planning to control aquatic weeds is extremely important. Water hyacinth, Eichhornia crassipes (Mart.) Solms, is one of the world’s worst pests with a bad reputation as an invasive weed. In this study we are seeking the possibility of using certain chemicals with a natural background, for controlling water hyacinth since there is a delicate balance that needs to be taken into account when using herbicides in water. Five compounds, namely: acetic acid, citric acid, formic acid, and propionic acid, in three concentrations (10, 15, and 20%) were applied (i.e. as a foliar application under wire-house conditions) and compared with the use of the herbicide glyphosate (1.8 kg ∙ ha–1). All of the five compounds performed well in the control of the water hyacinth. As expected, the efficacy increased as the concentration was increased from 10 to 20%. With formic and propionic acids, the plants died earlier than when the other acids or the herbicide glyphosate, were used. Acetic acid came after formic and propionic acids in terms of efficacy. Citric acid ranked last. Formic acid/propionic acid mixtures showed superior activity in suppressing water hyacinth growth especially at the rate of (8 : 2) at the different examined concentrations (3 or 5 or 10%) compared to the formic acid/acetic acid mixtures. Using the formic acid/propionic acid mixture (8 : 2; at 3%) in the open field, provided good control and confirmed the viability of these chemicals in the effective control of water hyacinth. Eventually, these chemical treatments could be used on water for controlling water hyacinth. In the future, these chemicals could probably replace the traditional herbicides widely used in this regard. These chemicals are perceived as environmentally benign for their rapid degradation to carbon dioxide and water. For maximum efficiency thorough coverage especially in bright sunlight is essential.
The water hyacinth, Eichhorrnia crassipes, has been widely recognized as the worst aquatic weed the world over and of increasing importance in Africa, Ethiopia inclusive. The aim of the research was to highlight the devastating impact of the water hyacinth on aquatic life and human activities on Aba Samuel Dam and to underline prospects of its beneficial use. Delphi technique and on-site observations were used. Eutrophication was found to be the main cause of the proliferation of the plant. However, a majority of its potential uses were identified. The absence of a distinct Ministry of Environment is retarding the efforts in fighting causes of water hyacinth spreading. Community awareness has also been identified as a vital component in eradication of water hyacinth. This research is of significant relevance to environmentalists and ecohydrologists in formulating appropriate strategies and policies for hampering proliferation of the weed.
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