| dc.description.abstract | Accelerated settlement and industrialization around Lake Victoria have led to alarming pollution levels in the lake. Water hyacinth (Eichhornia crassipes [Mart.] Sol. Laub.) that thrives best in polluted waters has therefore found a favourable niche in the lake. Though the water hyacinth is a bio cleaning agent that would be necessary to have in such waters, its growth and biomass accumulation makes it have a propensity for blocking the economic use of the lake, hence the need for its control. Control effort has involved the development of vegetable oil formulations. These control methods have lacked standardized inoculums concentration. There is therefore a need for coming up with a pathogen formulation in locally available material that has known inoculum concentration for easy use by the stakeholders. There are unanswered questions regarding the efficacy of mycoherbicides with varied inoculum concentrations. There are limited studies that have been done to test the host reaction of water hyacinth, in terms of leaf spot intensity, under varying inoculum levels. The purpose of this study was to determine the effect of corn oil emulsion formulation of Cercospora piaropiTharp and Myrothecium roridumTode Fries in the control of water hyacinth under greenhouse conditions in Kibos, Kenya. The objectives of the study were to determine the effect of corn oil spore concentrations of C. piaropi and M. roridumon; disease severity, disease incidence, relative shoot length and relative biomass of water hyacinth. The study was carried out at KALRO Kibos greenhouse located at latitude 00 37’ S and longitude 370 20’ E. The greenhouse conditions were25 to 300C and 22 to 270C temperature averages during the day and night respectively and 60 to 69% relative humidity. Plants symptomatic to C. piaropi and M. roridum leaf spots were sampled from Dunga Beach of Lake Victoria. The pathogens were aseptically cultured on PDA until sporulation, harvested and formulated in corn oil. Through serial dilution, corn oil formulations of 1x105, 1x106, 1x107, 1x108 and 1x109spores/ml of each of the pathogens were attained to form 6 treatments. Healthy water hyacinth plants with 50 to100 cm2leaf area were selected for the trial. The plants were separately misted with100ml of the corn oil formulations using hand sprayers held at 450 and 30cm from the plants. Control plants were not inoculated but misted with 100mlcorn oil emulsion without the pathogens. Both inoculated and control plants were placed in3 foot diameter and 1.5 cm depth basins filled with 20 liters of aged tap water. The experiment was laid out in completely randomized design with three replications. Disease severity (DS) score, disease incidence (DI),relative shoot length (R)and relative biomass (I) were determined at 2, 4 and 6 weeks after inoculation.DS scores were converted to area under disease progress stairs (AUDPS). Analysis of variance on mean DS, AUDPS, DI,R and I was done using PRO GLM in SAS (Institute, Inc.1999) computer software and LSD (p≤0.05) used for mean separation. Disease severity scores for both pathogens showed a significant (p≤0.05) increase as the concentration of spores in the formulations increased. The highest DS score was 5.00and 4.67 for C. piaropi and M. roridum respectively at week six at concentrations of 1x108 spores /ml. The respective AUDPS values for the two pathogens were significantly different with 20.67 for C. piaropi and 18.50 for M. roridum. The highest DI values were 82.23% and 88.9% for C. piaropi and M. Roridum respectively at week six at1x109 spores/ml. Compared to the control, Cercospora piaropi had relative shoot length of 55.07% while M. roridum had 51.93% for 1x109 spore/ml at week six. Relative biomass was significantly increased to a high of 73.53%for C. piaropiat 1x109 spore/ml. In conclusion, that C. piaropi and M.roridumin corn oil formulation were deemed feasible mycoherbicides in the greenhouse with spore concentrations of 1x108and 1x109spores/ml being most effective. Therefore any of the two bio pathogens can be formulated in corn oil at spore concentrations of 1x108or 1x109spores/ml for adoption in the control of water hyacinth in Lake Victoria | en_US |
