STUDIES ON POWDERY MILDEW OF OKRA (Abelmoschus esculentus(L.) Moench)
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Date
2014
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UHF,NAUNI
Abstract
ABSTRACT
Powdery mildew (Erysiphe cichoracearum DC.) is an important disease of okra in
Himachal Pradesh. Present investigations were undertaken with an objective to study the
occurrence, symptomatology, correct identity of the pathogen involved, pathogenicity,
relationship of environmental factors with disease development, screening of germplasm and
to evolve an effective disease management strategy. The disease was found prevalent in
moderate to severe form in Solan and Sirmaur districts of Himachal Pradesh. The
characteristic symptoms were observed on leaves, petioles and stems while no symptoms
were observed on the fruit. On the basis of anamorphic characters like ectophytic mycelium,
unbranched conidiophores with cylindrical foot cell, oval to roundish or barrel shaped
conidia, size, absence of fibrosin bodies in conidium, simple and straight germ tube and
presence of appressoria, the associated pathogen was identified as Erysiphe cichoracearum
DC. as the causal agent of the disease in Solan andSirmaur districts of Himachal Pradesh.
Pathogenicity test showed that both i.e. cotyledonary and first true leaves were susceptible.
Maximum conidial germination and germ tube length was recorded at 25
o
C temperature and
70.4 per cent relative humidity. Moderate air temperature of 25 ± 1°C coupled with slightly
less relative humidity (<70%) and less cumulative rainfall helped significantly in disease
development. Three cvs./lines like Shakti, MH-73, VRO-5 were observed as resistant while
fifteen cvs./lines were moderately susceptible. Among all the fungicides evaluated,
carbendazim proved most effective at all concentrations followed by dinocap (300 ppm) and
wettable sulphur (1000 ppm) and completely checked the conidial germination and germ tube
length under in vitro conditions. In field experiments, among different fungicides
difenoconazole sprays were significantly most effective followed by hexaconazole in
reducing the severity of powdery mildew and increased fruit yield. Among different natural
products and botanicals a combination of fermented cow urine + fermented butter milk
(10%+10%) was statistically superior and reduced the powdery mildew severity and increased
fruit yield.
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