Fungi That Affect Hibiscus
Black Spot
The leaf symptoms of this disease begin as pinhead size brown sunken
spots.
They usually increase in size & large areas of the leaf may be
affected.
Leaves eventually yellow & fall from the Hibiscus.
in sever cases the green parts of the stem may be attacked working
its way up & down the stem.
Black spot prefer an enviroment of high humidity & low air circulation.
It is most common in Spring & Autumn.
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Black Spot On Hibiscus Leaves
Size: X .10
Damping Off
Hibiscus seedlings soon die after germination.
Infection often affects discrete areas so that the distribution of
survivors is patchy.
Pythium sp. (Damping Off) attacks the young roots & soft stems
& these tissues become water soaked & darken with age.
Rhizoctonia sp. causes root & stem rots but under excessively moist
conditions it can develop aerial reddish gold webbing between the seedlings.
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Damping Off Of Seedlings
Size: X .05
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Damping Off Of Established Plants
Sizes: X .05
Fly Speck
This fungal disease is more likely in humid areas or if the Hibiscus
is in a shady position in the garden.
The rings form & the leaf gradually yellow & may fall The black
specks in the picture are the fruiting bodies & they are not always
clearly visible.
Some hibiscus are more prone to this fungus than others.
Golden Belle is one that comes to mind of being attacked.
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Fly Speck Fungi
On Hibiscus Leaf
Size: X 1.0
Grey Mould
A form of Botrytis spp. which are a major problem in propagation &
storage.
Hibiscus are prone to grey mould in the cooler times of the year when
the humidity is high the disease may enter at the axil of the bud or an
open wound working its way up & down the stem girdling the branch.
Flower buds of Hibiscus when infected will fail to open & will
decay on the plant without absission (falling off).
In both cases there may be masses of grey sporulation which are visible
on the affected tissue.
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Grey Mould (Botrytis) On Hibiscus Floral
Buds & Stem
Sizes: X 3.0
.............X 1.0..................................X
1.0
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Root Rot
The Fungi Phytophthora is among the most important unrecognised causes
of Hibiscus losses in the ground & in containers.
Black or brown root rot often extending into the stem.
Rots can resemble bacterial soft rots which is often a secondary infection
to the plant tissue.
Affected Hibiscus are unthrifty & eventually die.
Root damage can be detected by periodically tipping the plant out of
the pot or scratching the surface of the inground Hibiscus.
The cream white root colouring are indications of healthy root system.
The colouration of black / brown roots are indicators of infection.
The disease is spread via untreated water or implements coming in contact
with infected soil.
The disease is worse in poorly drained soils & potting mixes.
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Hibiscus Root Rot
Size: X .50
..
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Hibiscus Root Rot
At Different Stages
Size: X .05
.
...
Collar Rot Of Hibiscus
Size: X 2.0
Sooty Mould
Sooty mould is identified by a black sooty growth covering the foliage.
This fungus grows superficially on sugary secretions on the surface
of Hibiscus.
Although generally not pathogenic, sooty mould can cause problems during
the hibiscus growing functions by reducing the amount of light to strike
the leaf & reducing the plant's ability to photosynthesise properly.
The appearance of sooty mould often indicates the presence of sap sucking
insects such as scale, aphids
& mealy bugs.
Control these pests & you will control Sooty Mould.
..
Sooty Mould
On Hibiscus Leaf
Size: X .5
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Lichen
Any of a group of composite organisms made up of a fungus and an alga
living in symbiotic association . The fungus absorbs water that is used
by the alga in photosynthesis; the alga synthesizes and excretes a specific
carbohydrate that the fungus is able to take up and utilize as food.
About 15,000 kinds of lichens have been described. They are found worldwide,
especially in harsh environments, usually on rock, bark, or poor soil.
The body, or thallus, has a characteristic growth form: Unique substances
synthesized by lichens are responsible for their colors of greenish gray
to yellow & orange.
They are sometimes present on the trunks of very old hibiscus &
are only a bother to the appearance of the plant.
.
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Two Forms Of Lichen Attached To
Bark
Size: X 5.0
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