STUDIES ON THE PREVALENCE AND EPIDEMIOLOGY OF APPLE POWDERY MILDEW IN HIMACHAL PRADESH
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Date
2022-05
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UHF,NAUNI
Abstract
ABSTRACT
Powdery mildew of apple was found prevalent in moderate to severe forms in Kalpa and
Nichar block of Kinnaur, Himachal Pradesh. Incidence of the disease ranged from 25.42 per cent to
53.80 per cent and severity from 39.75 per cent to 66.25 per cent, respectively. Overall twenty
different apple cultivars were screened against powdery mildew planted under field conditions at
KVK Sharbo, Kinnaur, H.P. Out of the 20 cultivars 5 cultivars viz. Red Delicious, Royal Delicious,
Red Velox, Auvil Early Fuji and Oregon Spur II, were found to be less susceptible to Podosphaera
leucotricha, while Granny Smith, Golden Delicious, and Gale Gala were found extremely susceptible.
In the pathogenicity test of Podosphaera leucotricha it was observed that the symptoms developed at
12 days after inoculation. Small whitish felt-like patches of fungal growth appeared and quickly
covered the entire leaf. According to the present study the disease initiated during first week of May
and peaked in the month of July in district Kinnaur. Temperatures between 18-240 C and RH between
50-65 per cent were favourable for the disease development. For the management of the disease, in
vitro evaluation of fungitoxicants was done against Podosphaera leucotricha by slide germination
method. Boscalid + Pyraclostrobin (100.00), Fluxapyroxad + Difenoconazole (95.91%) and
Tebuconazole + Trifloxystrobin (94.78%) were found to be superior over other fungicides in
inhibiting the spore germination at all the tested concentrations. The same set of fungicides evaluated
in vitro were sprayed under field conditions and maximum disease control (94.04%) was reported in
Fluxapyroxad + Difenoconazole treated plots followed by Boscalid + Pyraclostrobin (89.92%). These
fungicides were further evaluated under nursery conditions. Here maximum disease control (81.09%)
was registered in Fluxapyroxad + Difenoconazole followed by Boscalid + Pyraclostrobin (79.51%).
For the perpetuation of fungus Podosphaera leucotricha leaves and twigs were collected from
orchards and found that fungus survived and perpetuated in the form of conidia, mycelium and
chasmothecia in the dormant buds and twigs of the tree.