STUDIES ON THE MANAGEMENT OF LEAF BLIGHT OF GRAPE CAUSED BY Alternaria vitis (Cav.) Sacc.
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Date
2006
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
Studies were carried out to derive a suitable management strategy for
Alternaria leaf blight of grapevine caused by Alternaria vitis (cav.) sacc.
which is becoming serious in Andhra Pradesh.
The cold sterilised extracts of different fermented materials (Neem
seed kernels, Vermicompost, Sugarcane press mud, FYM + Paddy straw,
FYM + Fish meal + Cellulose and Grape berries), fungicides, salicylic acid
and biocontrol agents were tested against the mycelial growth and spore
germination of pathogen.
Grape berry fermented juice is superior over all other treatments in
inhibiting the mycelial growth as well as spore germination of Alternaria
vitis, at its higher concentration. 10 day fermented juice is more effective
compared to 20 and 30 day fermented extracts. This is followed by neem
seed kernel extract. Other water extracts of composts considerably inhibited
the spore germination but not the mycelial growth.
Among the fungicides tested Iprodione 25% + Carbendazim 25%
(Quintal) at 0.1% and Indofil M-45(Mancozeb) at 0.25% completely (100%)
inhibited the mycelial growth and spore germination of pathogen. Iprodione
25% + carbendazim 25% (Quintal) at 0.05% given 100% inhibition of
mycelial growth.
Salicylic acid is not consistent in its performance in inhibiting the
mycelial growth. The maximum inhibition was 14.05% at its higher test
concentration of 125 ppm. At the same concentrations it inhibited the spore
germination upto 45.62%.
The biocontrol agents Trichoderma viride and Pseudomonas
fluorescens showed 66.67% and 55.6% of inhibitions respectively.
The microflora, isolated from the grapevine phylloplane include ten
fungal species like Trichoderma harzianum, T. viride, Aspergillus niger,
A. tumarii, A. fumigatus, Paecilomyces variotii, Thielavia terricola,
Cladosporium cladosporoides, Oidiodendron sp., Alternaria sp. and five
bacterial isolates PPB-1Y , PPB-2R, PPB-3Ro, PPB-4W, PPB-5Cr. were
observed. Among the fungi Trichoderma harzianum recorded highest
mycelial growth inhibition of 72.8% and Pseudomonas fluorescens was the
best among the bacteria with 65.91% growth inhibition and 5.34mm of
inhibition zone.
The treatments, which were proved effective in in vitro studies, were
tested in the glass house on grapevine rooted cuttings of Thompson seedless
variety for their efficacy against the Alternaria leaf blight. In all the methods
of testing 10 day unsterilised grape berry fermented juice recorded
minimum Percent Disease Index. Prophylactic application of 10 day
unsterilised grape berry fermented juice at 25% and Iprodione25% +
Carbendazim25% (Quintal) at 0.1% recorded minimum Percent Disease
Index of 14.8% each followed by native Trichoderma harzianum, native
Pseudomonas fluorescens with 17.29% each and Pseudomonas fluorescens
(Bio control agent) with 22.23%. All the treatments were considerably
effective in reducing the Percent Disease Index.
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Keywords
STUDIES, MANAGEMENT, LEAF, BLIGHT, GRAPE, CAUSED