STUDIES ON ALTERNARIA LEAF SPOT OF BRINJAL
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Date
2019-11
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UHF,NAUNI
Abstract
ABSTRACT
Alternaria blight caused by Alternaria alternata (Fr.) Keissler has been observed as one of
the important disease in brinjal growing areas of Himachal Pradesh. The survey and surveillance
studies revealed that disease appeared in moderate to a severe form in different localities of Solan,
Bilaspur and Mandi districts of Himachal Pradesh during the 2018 cropping season. The pure culture
of the pathogen was isolated over PDA. Morphological studies revealed olive-green to dark brown
colour colonies with zonation, dark colour septate hyphae, obclavate to pyriform, golden to dark
brown conidia with regular transverse and longitudinal septa and comparatively smaller beak. On the
basis of cultural and morphological characters, the pathogen was identified as Alternaria alternata
(Fr.) Keissler. The pathogen exhibited initial symptoms after 120, 62 and 75 h of inoculation on
potted plants, detached leaves, and detached fruit respectively. The symptoms initiated as the
formation of yellow fleck on leaves which turned brown necrotic irregular to circular spot surrounded
by a yellow halo. The further enlargement and coalescing of these spots resulted in blightning of leaf
lamina followed by drying of the leaf. The temperature of 25ºC and pH of 6.5 were found optimum
for mycelial growth and dry mycelial weight respectively. The epidemiological study revealed the
temperature of 25ºC, RH of >90% and leaf wetness period >16h as most conducive for rapid disease
progression reflecting the high apparent rate of infection. Survival studies indicated a significant
decrease in the survivability of pathogen with increasing duration of storage and depth of burial. In
vitro evaluation of fungicides revealed Folicur, Contaf, and Tilt as most efficacious fungicide in
inhibiting the mycelial growth of Alternaria alternata, while among botanicals garlic clove extract
and Darek extract provided significantly high inhibitory responses. Field evaluation studies referred
the application of four foliar sprays of Contaf (hexaconazole) @ 0.05 per cent at 10-day interval
started with the initiation of disease as most efficacious in limiting the Alternaria blight of brinjal
(80.33%) and enhancing the fruit yield (156.90q/ha) with ICBR of 1:15.27.
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