Etiology and management of powdery mildew disease of pumpkin (Cucurbita moschata Poir)
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Date
1992
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Department of Plant Pathology, College of Horticulture, Vellanikkara
Abstract
The present investigation was undertaken to correctly identify the causal organism of pumpkin powdery mildew disease in Kerala and to find out the environmental factors responsible for the occurrence of infection. Attempts were also made to screen different pumpkin lines to identify resistant ones to powdery mildew. The efficacy of different antifungal compounds against the disease were also tried.
The study was conducted during 1990 -92 at College of Horticulture, Vellanikkara. Detailed symptomatology of the disease was worked out. The time taken for getting infection varied in resistant moderately resistant and susceptible plants. The fungus causing powdery mildew disease of pumpkin in Kerala was identified as Sphaerotheca fuliginea (Schlecht) Poll. Teleomorphic stage of the pathogen was not observed.
From the cross inoculation studies it was clear that S. fuliginea from pumpkin cannot infect non-cucurbitaceous crops and weeds. Even in cucurbits it could infect only bittergourd and ivy gourd. The optimum temperature for germination of S. fuliginea was at 25°C followed by 20°C. The spores germinated at very high relative humidity while it was inhibited in water.
Preliminary screening of 57 lines of pumpkin was conducted during 1990 season and 28 lines were selected from this for further studies. All the lines were found infected in both the seasons. But the degree of susceptibility and the age at which they became susceptible were varied. Only the line showed consistency in resistant reaction. Climatic factors like temperature, relative humidity, rainfall and sunshine hours were recorded for an year and was correlated with the disease severity. Incidence of the disease was indirectly correlated with rainfall. However, the influence of climatic factors were more pronounced during the initial stages of the crop. Laboratory and field experiments were conducted to find out the efficacy of five antifungal compounds and water on S. fuliginea. All the chemicals and water inhibited spore germination at varying concentrations. Effect of those chemicals and water were also tried under field conditions on line P. 46. At the end ofone week after spraying Carbendazim recorded maximum disease reduction. Disease at the time of harvest was least in Sulfex treated plants. Even water spray could reduce the disease considerably. Maximum yield was recorded from plants sprayed with Calixin. The best cost effective method to check powdery mildew infection of pumpkin was by spraying water.
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