MSc

The study entitled ‘Integrated management of Pythium stem rot of vegetable cowpea (Vigna unguiculata sub sp. sesquipedalis (L.) Verdcourt )’ was conducted during the period 2012-2014 at College of Agriculture, Vellayani, Thiruvanathapuram to investigate the stem rot disease of cowpea caused by Pythium spp. and to evolve an integrated management package for the control of the disease.
Eight pathogen isolates were collected from the different locations of Thiruvanathapuram district. From this the most virulent pathogen isolate was selected for the study. The pathogen isolated was identified as Pythium aphanidermatum based on cultural and morphological studies. PSA was found to be the best solid medium at 35 to 400C at pH 6 to 8 range under full darkness whereas PSB and PDB broths were the best liquid media for supporting the growth of the pathogen at 30 to 350C at pH5.5 under any light conditions.
The survival studies of the pathogen, P. aphanidermatum revealed that oospores were the main survival propagules help for 15 weeks survival on crop debris. Correlation studies on the influence of weather parameters on the disease incidence indicated that the disease was negatively correlated with maximum temperature and soil temperature. The host range study indicated that snake gourd at flowering stage, tomato, chilly and red amaranthus at seedling stage was found to be collateral hosts, none of the weeds artifically inoculated were found to take up the infection.
The biocontrol agents (KAU cultures) Pseudomonas fluorescens and Trichoderma sp. gave moderate inhibition of the mycelial growth of the pathogen. In organic preparations, Panchagavya gave complete inhibition of the growth of the pathogen at all concentrations tested whereas the fish amino acid gave full inhibition only at 10% concentration. In the fungicides in vitro assay, three fungicides copper oxychloride, copper hydroxide and metalaxyl MZ gave good suppression of the pathogen growth at all concentrations.
The results of the in vitro seedling assay experiment revealed that the percentage seedling mortality was lowest for the three fungicides treatments i.e., copper oxychloride, metalaxyl MZ and azoxystrobin and one KAU released biocontrol agent Trichoderma sp..
The result of the field experiment showed as a chemical management, foliar spraying and soil drenching of metalaxyl MZ (0.2%) or azoxystrobin (0.15%) or fish amino acid (5%) or panchgavya (5%) or copper oxychloride (2%) or Pseudomonas fluorescens or Trichoderma sp.@ 2% of the talc based formulation or soil drenching with copper oxychloride (2%) at 2 weeks after planting at 10 days interval could control the disease effectively.
In the case of severe, endemic occurrence of the disease, chemical control by spraying and drenching with metalaxyl MZ (0.2%) or azoxystrobin (0.15%) or soil drenching with copper oxychloride (0.2%) can be recommended (10 days interval). In a condition where organic disease management needed the result of this study indicates the prophylactic drenching of copper oxychloride (0.2%) or spraying and drenching of fish amino acid (5%) or Panchagavya (5%) or the use of spraying of KAU released bioagents Pseudomonas fluorescens or Trichoderma sp.@ 2% two weeks after planting at 10 days interval can be recommended