STUDIES ON THE PERPETUATION OF Diplocarpon mali CAUSING PREMATURE LEAF FALL OF APPLE AND ITS MANAGEMENT
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Date
2014
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
UHF,NAUNI
Abstract
ABSTRACT
Premature leaf fall is one of the most important diseases of apple particularly in Himachal
Pradesh. Present studies were carried out with the objectives to study the mode of survival of
Diplocarpon mali in the infected leaf litter, to study the effect of time of leaf fall, cultivar and
environment on the perennation of Diplocarpon mali and to devise methods of its management by
suppressing the perennating inoculum in the field. Acervuli of Marssonina coronaria were found to
occur in all the leaf samples while conidia formation started in or after May ranging from 1.2x10
3
to
5.8x10
3
conidia per ml at all the locations but its ascosporic stage and apothecia were not observed in
any of the leaf samples. Leaves collected on September 28, 2013 produced the highest number of
conidia (5x10
3
conidia/ml) in the summer and the conidial production started from pea stage of apple
bud development and the maximum production of primary inoculum was observed at pre-harvest stage
(9.2x10
3
conidia/ml). Maximum number of conidia were caught on the greased slides on 7
th
August
2014, when the temperature was 19
0
C with ample rainfall and relative humidity above 85 per cent in
the preceding 24 hours. Also, rainfall and relativehumidity were significantly and positively correlated
with number of conidia released in the apple orchard, whereas, the maximum temperature showed a
negative correlation. Among the test apple cultivars, Golden Delicious produced maximum number of
conidia in the overwintered leaf litter followed byRoyal Delicious, Red Gold, Rich-a-Red, Scarlet Gala
and Tydeman’s Early Worcester and Granny Smith. Among the antagonists, Pseudomonas fluorescens
was found to be the most effective and significantly superior with overall reduction in conidial
production of 71.17 per cent followed by Trichoderma viride with 66.02 per cent reduction, Bacillus
subtilis (58.73%), T. harzianum (55.29%) and T. hamatum with 50.23 per cent reduction of the
primary inoculum. Urea (5%) dip treatment suppressed the conidial production to the extent of 83.42
per cent followed by its lower concentrations. Carbendazim was found to be the most effective and
significantly superior among all the fungicidal dip treatments with 76.70 per cent inhibition in
production of primary inoculum followed by pyraclostrobin + metiram, mancozeb and copper
oxychloride with 65.95, 46.60 and 41.05 per cent inhibition, respectively.
Description
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