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Articles by J.M. Wagacha
Total Records ( 4 ) for J.M. Wagacha
  J.W. Muthomi , P.E. Otieno , G.N. Chemining wa , J.H. Nderitu and J.M. Wagacha
  Greenhouse experiments were conducted over two cropping cycles to investigate the effect of fungicide seed treatment and fungal root rot pathogens on nodulation and dry matter accumulation of selected food legumes. The legumes were common bean (Phaseolus vulgaris L. variety GLP 2), green gram (Vigna radiata L. variety M66) and lablab (Lablab purpureus L.) while the pathogens were Fusarium oxysporum f. sp. phaseoli, Macrophomina phaseolina, Sclerotinia sclerotiorum and Rhizoctonia solani. Treatments consisted of inoculation of legume seeds with appropriate rhizobia alone, rhizobia together with fungicide, rhizobia together with pathogen and a combination of rhizobia, fungicide and pathogen. Fungicide copper oxychloride was used as a seed dresser. Rhizoctonia solani and S. sclerotiorum were more pathogenic and showed significantly increased seedling mortality and greater reduction in seedling emergence, number of nodules and root dry matter. Fungicide seed dressing significantly increased seedling emergence and reduced seedling mortality. However, fungicide seed dressing alone and in combination with pathogen depressed nodulation in all the legumes. Inoculation with F. oxysporum and M. phaseolina had no significant effect on nodulation in common bean. All the treatments had little or no significant effect on shoot dry matter. The results suggest that fungicide seed treatment in combination with rhizobia inoculation is beneficial in management of root rot and enhancement of nodulation in food legumes.
  J.W. Muthomi , G.M. Riungu , J.K. Ndung`u , R.D. Narla , J.K. Gathumbi and J.M. Wagacha
  The study was carried out during the 2006 cropping season in Nakuru district, Kenya. Incidence and severity of head blight were determined and pathogens isolated from diseased wheat heads, wheat and maize kernels. Mycotoxin deoxynivalenol content in grain was determined by direct competitive Enzyme-Linked Immunosorbent Assay (ELISA). Pathogenicity of different Fusarium species isolated from wheat was determined by inoculation onto wheat ears in greenhouse. Head blight was highly prevalent (90-100%) and mean incidence and severity ranged from 4 to 9% and 15 to 37%, respectively. Fusarium was most prevalent in infected wheat heads while Epicoccum was most prevalent in harvested wheat grain. Only Fusarium spp. and Penicillium spp. contaminated harvested maize grain. The most frequently isolated Fusarium species were F. poae, F. graminearum and F. chlamydosporum in wheat and F. verticilloides in maize. Most wheat and maize grain samples were contaminated with mycotoxin (DON), with concentration ranging from 0-1,200 and 0-4,600 µg kg-1, respectively. Fusarium graminearum isolates were highly pathogenic, significantly reducing kernel weight. The results suggest that head blight in Nakuru district is due to a complex of Fusarium species with F. graminearum being the major pathogen. Cross-contamination of wheat and maize is implied, indicating possible contamination of wheat maize products with deoxynivalenol mycotoxin.
  N.K. Njeru , J.W. Muthomi , C.K. Mutegi and J.M. Wagacha
  Fusarium head blight (FHB) is an economically important disease of wheat, which causes reduction in grain yield both quantitatively through reduced seed weight and qualitatively by contaminating grains with mycotoxins. The effect of cropping systems on accumulation of FHB inocula in crop residues and soil was assessed at hard dough stage of wheat during the 2013 cropping season in three agro-ecological zones in Narok County, Kenya. A semi structured questionnaire was used to obtain information on wheat production practices. Fusarium spp. were isolated from crop residues and top soil, while incidence and severity of FHB were assessed at mid-anthesis. Majority of the wheat farmers were small scale producers who rotated wheat with maize, grew the two crops in adjacent fields, grew wheat in consecutive years, left wheat residues as standing hay for livestock and practiced simple land preparation methods. Prevalence of FHB was 100%, while mean incidence and severity were 20.7 and 28.4%, respectively. The most frequently isolated Fusarium spp. were F. chlamydosporum and F. graminearum in crop residues and F. oxysporum and F. proliferatum in soil. The incidence of Fusarium spp. in soil and crop residues was highly correlated to FHB incidence but not to severity of the disease. Wheat production practices affect the survival of Fusarium spp. in soil and crop residues between cropping seasons. It is therefore, recommended that after harvesting, wheat straw and maize stover should be removed from the field or be incorporated into the soil through tillage to allow faster decomposition. Inclusion of maize as a rotation crop in wheat production should also be avoided.
  G.M. Riungu , J.W. Muthomi , R.D. Narla , J.M. Wagacha and J.K. Gathumbi
  Laboratory and green house studies were conducted at the Faculty of Agriculture, University of Nairobi, to evaluate the efficacy of Epicoccum sp., Alternaria sp., Trichoderma sp. and Bacillus sp. in control of Fusarium head blight of wheat caused by F. graminearum. Fungicides folicur® and copper oxychloride were used as standard checks. Laboratory assay was carried out by paired cultures and antagonism was measured as reduction in pathogen colony diameter. Green house experiments involved dual inoculation of pathogen and antagonist onto wheat ears and head blight severity and grain yield determined. Doxynivalenol content in the resulting grain was determined by competitive direct ELISA. The antagonists and fungicides significantly reduced the growth of Fusarium graminearum colonies in culture. Folicur® and copper oxychloride completely inhibited the growth of the pathogen while Trichoderma sp. showed 64% colony growth reduction. However, the antagonists showed limited reduction in head blight severity in green house trials. Trichoderma sp. reduced head blight severity by 18% while folicur® reduced the disease by 28%. All the antagonists had little or no significant effect on grain yield. Only folicur®, copper oxychloride and Alternaria sp. reduced DON in grain by 76 to 93%. Obtained results indicate that microbial antagonists may offer potential benefit in FHB management and screening of more antagonists both under controlled and field conditions is necessary.
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