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DISEASE DEVELOPMENT AND MANAGEMENT OF LEAF BLIGHT [Stemphylium vesicarium (Wallr.) E. Simmons] OF GARLIC (Allium sativum L.)

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Title DISEASE DEVELOPMENT AND MANAGEMENT OF LEAF BLIGHT [Stemphylium vesicarium (Wallr.) E. Simmons] OF GARLIC (Allium sativum L.)
 
Creator KAPADIYA ITESHKUMAR BHUPATBHAI
 
Contributor LUKOSE C.
 
Subject GARLIC
PLANT PATHOLOGY
 
Description Key words: Garlic, leaf blight, Stemphylium vesicarium, disease development, management
Garlic (Allium sativum L.) belonging to the family Alliaceae is the second most important bulb crop grown throughout the plains of India for spices and condiments. Though, garlic is seriously affected by many diseases, leaf blight caused by Stemphylium vesicarium (Wallr.) E. Simmons is an important destructive disease. It appears every year in a moderate to severe form in garlic growing areas of Saurashtra region of Gujarat.
The causative organism isolated from the infected leaves of the diseased plants of garlic grew in the form as dark green to blackish mycelium, which later turned olivaceous brown to black and finally velvety on PDA. Conidia were light brown or golden brown to olive brown, oblong or broadly oval, producing on straight to variously curved cylindrical and septate conidiophores. Based on the morphological characters viz., mycelium, conidiophores, conidia and growth patterns, the causative fungus isolated from the leaves of infected garlic plant was identified as Stemphylium vesicarium (Wallr.) E. Simmons.
Garlic plants were susceptible to leaf blight from 30 to 35 days of growth, but it was more prominent at 50 days onwards. Initially the infected plants exhibited characteristic symptoms of white flecks that enlarged and produced sunken purple lesions which were surrounded by a yellow to pale brown border. Later, small light yellow to brown, water soaked and non-delineated lesions developed on older leaves. Finally, these lesions grew into elongated spots that frequently coalesced resulting in blighting of leaves.
The pathogenicity of S. vesicarium was confirmed by reproducing the same field symptoms like discolouration and withering of the leaves. Re-isolations confirmed the pathogenicity of S. vesicarium as the infected tissues produced the same type of mycelial growth, conidiophores and conidia of the original fungus.
The study on different dates of sowing on the development of Stemphylium leaf blight intensity revealed that the severity was higher in the crop sown during 3rd week of October. However, in the crop sown during the 1st and 3rd weeks of November had the lowest disease intensity as compared to the crop sown on the 3rd week of October. Although, the lowest disease severity among all the different dates of sowing was recorded in delayed sowing i.e., by the 1st week of December, it may reduce the germination of garlic cloves.
Epidemiological study revealed that the progress of Stemphylium leaf blight of garlic was affected by variation in weather variables as well as by their interactions. There was a progressive increase and maximum per cent disease intensity was recorded in 17th to 18th week after sowing.
During 2012-13, the high wind speed stimulated the development of Stemphylium blight as the coefficient of the wind speed was positive and highly significant at 1% level of significance. Likewise, the coefficient of morning humidity was positive and significant at 5% level of significance. This indicated that the increase in morning humidity by 1% increased the development of blight. Likewise, during the year 2013-14 the wind speed had significant and positive effect on the development of blight. The maximum temperature also had positive and significant effect on the development of blight. Other variables like minimum temperature and evening humidity had no significant impact on development of blight in garlic.
Out of the fourteen garlic germplasm/varieties screened under natural conditions, none of the entries was immune or resistant to Stemphylium leaf blight. However, DG-08-17 was moderately resistant and DG-08-21 was moderately susceptible to leaf blight. The remaining twelve entries were susceptible with an average disease intensity of 32-46%.
Experiment conducted in pots to know the leaf blight disease development at different ages viz., 30, 40, 50, 60 and 70 days indicated that the plants of all ages were almost susceptible to leaf blight disease. However, the plants between the age of 50 and 70 DAS were more susceptible to Stemphylium blight than 30 and 40 days old seedlings. As the incubation period increased from 10 to 20 days, irrespective of the age of plant, the development of leaf blight also increased correspondingly.
Though all the eight fungicides tested were capable of inhibiting the growth of S. vesicarium at recommended concentration under in vitro, propiconazole, tebuconazole and difenoconazole were superior, whereas copper oxychloride was the least effective fungicide in inhibiting the growth.
Among the different fungicides tested as foliar spray under field conditions, the lowest blight intensity (22.0%) with the highest disease control (57.05%) was obtained in foliar application of propiconazole (0.05 %) followed by mancozeb (0.2 %). The maximum bulb yield of 4540 kg/ha was also recorded in foliar spray of propiconazole.
The survey conducted in twenty garlic fields from ten villages of Junagadh district revealed that the intensity of Stemphylium blight ranged from 12.5 to 50.4%. The maximum intensity of disease was recorded in Sarsai village followed by Moniya village. The minimum mean disease intensity of 12.5 and 16.4% were recorded from Bhesan and Bilkha villages, respectively. However, none of the garlic fields surveyed were free from leaf blight.
 
Date 2016-09-28T17:53:01Z
2016-09-28T17:53:01Z
2015-01
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/79393
 
Language en
 
Format application/pdf