S T U D I E S ON THE E F F E C T S OF WEATHER P A R A M E T E R S ON I N C I D E N C E OF POWDERY M I L D E W ( U n c i n u l a necator ( S c h w . ) B u r r O N G R A P E S ( V i t i s vinifera L. )
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Date
1992
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mpkv, rahuri
Abstract
The experiment entitled, "Studies on the effects of weather parameters on
incidence of powdery mildew (Uncinula necator (Schw.) Burr.) on grapes (Vitis
vinifera L,)'\ was conducted during the post-monsoon season of the year 1990-
91. Five compartments, each consisting of nine vines, were erected with the help
of transparent polythene sheet and wooden frame and were irrigated at an
interval of 4, 8, 12, 16 and 20 d in order to create varying microclimatic
conditions in these compartments. The temperatures, within the canopy of vines,
in different compartments were recorded continuously by thermocouples and
relati\ v humidity, within the canopy, was recorded by thermocouple
psychrometer. Biological observations on per cent incidence of powdery mildew
on berries (% IN), spore load on berries (SL)( and per cent disease intensity on
leaves (PDI), were recorded at an interval of 3 d.
Th*» disease incidence and multiplication was rapid in the months of
December and January when the climate was cool and humid compared to the
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climate in the months of November and February. The vines suffered early and
more from the attack of disease where irrigations were applied at shorter
intervals than the vines irrigated at longer intervals. The most critical minimum
and maximum temperature for rapid multiplication of powdery mildew ranged from
10.80 to 15.52"C and 25.33 to 32,39'C with an average of 12.87 ± 1.39'C and 28.26
± 2.08*C, respectively. Similarly, the most critical relative humidity at 0730 h
and 1430 h was ranged between 88.33 to 96.77% and 57.39 to 62.68% with an
average of 92.76 ± 2.34% and 60.08 ± 2.22%, respectively.
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msc
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