Botany Department

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Botany Department
B.N.Bandodkar College
Fungal diseases in Orchids.
-- Mr. Omkar Ambadas Thorat
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MYCORRHIZAL ASSOCIATION IN ORCHIDS
Fungal infections lead to endotropic and
intracellular association. Peltons are formed in
the host cells. The digestion of fungus in the
host cells results in the utilization of nutrient
by the host cell.
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Fungi like Armlliaria, Rhizoctonia, Corticum,
Marasamius, Thanetophora and Glomus have been
found to form symbiotic association with orchids.
Marasamius pulcherripes
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Anthracnose
Anthracnose is a minor disease, often
superficial, caused by a variety of fungi.
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Distribution Worldwide
Under cool, wet conditions basal rot may develop.
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Causal organism Colletotrichum cinctum C.
gleosporiodes
Hosts Several species and hybrids in the genera
Aerides, Coelogyne, Dendrobium, Eria, etc.
Coelogyne sandariana
Aerides odorata
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Symptoms 1) Raised pustule.
2) Circular, oval spots. 3)
Color brown to dark brown or
grey.
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Control measures Eradicate all the diseased
parts/organs by burning. Spray Captan or Benomyl.
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Drought conditions should be avoided on turf
dominant in annual meadow-grass to ensure plants
are not stressed.
Daconil Weather Stik (chlorothalonil) and Banner
Maxx (propiconazole) will both control
anthracnose.
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Flower Rusty Spot
This disease is most prevalent during the wet
season and causes considerable loss to flower
production.
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Distribution Worldwide
This disease is found in various parts of world.
Causal organism Curvularia eragostidis
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Symptoms 1) Small rusty brown spots. 2)
Premature senescence.
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Control measures 1) Remove and eradicate all
the diseased flowers. 2) Irrigation with
chlorinated water. 3) Chlorinated water is
prepared by 5g chlorine dust in 20 lit. water.
4) Leave overnight yields for good results.
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Damping Off
This disease is observed in young seedlings with
soft tissues.
Phytophthora palmivora
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Distribution Worldwide.
It is found in different parts of world in
various forms.
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Causal organisms Phytophthora palmivora, P.
omnivora and Pythhium ultimum.
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Hosts Seedlings of many species and hybrids
including Cattleya, semiterete Vanda and Aranda.
Cattleya labiata
semiterete Vanda
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Symptoms 1) Watery spots on leaves. 2) They
turn yellow/black and die. 3) The roots
collapse and eventually the entire plant
dies.
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Control measures Sanitation, controlled
irrigation, sterile potting media and containers
and clean benches are usually recommended to
prevent damping off. Seedlings should be
drenched at seven-day intervals with 50 mg Dexon.
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NAME SUTVRE DEXON OREUND 26 MM  90 CMCODE
SD-ORREF 9819-61SIZE 30 75 CMBAND
SYNTURE
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It can also be done by mixing 1 part copper
sulphate in 100,000 parts of water.
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Thanks!