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. .
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. .
Damping Off Of Seedlings
Size: X .05
.
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. .
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. .
Grey Mould (Botrytis) On Hibiscus Floral Buds
& Stem
Sizes: X 3.0
.............X 1.0..................................X
1.0
.
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. .
Hibiscus Root Rot
Size: X .50
..
.
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
. 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. . .
