Transcript Black Leg of Geranium

Pathogens Covered
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Pythium spp.
Phytophthora spp.
Fusarium solani
Rhizoctonia solani
Black Leg of Geranium
Pythium spp.
Pythium Root Rot of Impatiens
Control:
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Take special care during transplanting to
avoid excessive planting depth and
wounding of stem and root tissue.
Avoid excessive soil compaction during
the transplant operation.
Water carefully; avoid overwatering.
Drench-applied fungicides can be
effective in controlling this disease
problem.
Phytophthora Damping Off
Phytophthora root rot
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Phytophthora root rot is caused by several species
of fungi in the genus Phytophthora.
Phytophthora cinnamomi is usually credited with
causing the greatest damage to container- and
field-grown woody ornamentals.
P. parasitica, P. citricola, and possibly P. cactorum,
are also known to attack woody plants, particularly
azaleas and rhododendrons.
Phytophthora cryptogea has been known to cause
heavy damage on junipers in poorly drained
landscape beds
Phytophthora Root Rot
Symptoms:
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Phytophthora root rot greatly reduces the volume of the roots
which are needed by the plant to absorb water and nutrients.
The roots on diseased plants are brittle and brown to reddishbrown in color.
A network of fine, discolored feeder roots may be confined to
one area or include the entire root system. The fungus
usually colonize the crown of the plants, often girdling the
stem at or just above the soil line. A brown to reddish-brown
discoloration of the tissues occurs just below the bark and
may extend up the stem above the soil line.
On some trees and large shrubs--such as dogwood--brown,
water-soaked cankers oozing a dark-colored fluid or gum may
develop at the soil line.
Phytophthora Root Rot
Symptoms:
Phytophthora Root Rot
Symptoms:
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These symptoms can easily be confused with those of
a nutritional disorder, overwatering, drought stress,
and a number of other factors and so can be
overlooked by the grower.
Slight yellowing of the leaves followed quickly by
permanent wilting and plant death are the symptoms
usually associated with Phytophthora root rot on
container-grown azaleas and rhododendrons
In landscapes, established plants may show symptoms
of general decline for one or more years before
succumbing to root rot, while newly planted azaleas
will quickly die.
Phytophthora Root Rot
Symptoms:
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Symptoms vary according to the degree of root
colonization by Phytophthora root rot fungi, plant age,
plant susceptibility to root rot, and environmental
stress.
Typically, symptoms first appear on one plant and later
on surrounding plants in both container areas and
landscape beds. Some yellowing of the foliage,
particularly at the shoot tips, leaf shed, slowed plant
growth, and possibly limb dieback may occur in early
stages of the disease
However, it is not uncommon for liners or containergrown plants to remain almost symptomless until after
transplanting into larger containers or landscape beds.
Phytophthora Root Rot of
Gardenia
Phytophthora
Symptoms:
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The foliage of azaleas and rhododendrons may also
be invaded by some Phytophthora root rot fungi.
Irregular blotches which are first olive-colored and
later brown, sometimes with a red margin, develop
on the leaves.
Diseased leaves are usually shed by the plant.
Damage usually appears on limbs near the base of
the plant.
Phytophthora Crown Rot –
Holiday Cactus
Phytophthora Crown Rot /
Poinsettia
Phytophthora / Poinsettia
Disease Cycle
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Phytophthora spp. survive as resting structures
(chlamydospores and oospores) and mycelia in
diseased roots, crowns, and other crop debris.
The resting structures are released into the soil or
potting media from infested crop debris and are
readily spread from pot to pot throughout propagation
and container production areas by soil and splashing
or flowing water.
Recycled irrigation and runoff water has been
implicated as a source of these fungi in rhododendron
nurseries.
Disease Cycle
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Heaviest losses to root rot in most container
production nurseries usually occur on flat, poorly
drained beds where water is allowed to stand
around container bases
Overwatering in the nursery or landscape will also
contribute to losses from the disease.
Phytophthora root rot is most commonly seen in
field production nurseries and landscape plantings
on poorly drained, waterlogged soils that are prone
to flood. Disease development is usually slow or
absent on well-drained sites.
Control:
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Prevention is the key to controlling Phytophthora root
rot in commercial nursery stock. Once symptoms start
to appear, much of the damage has already been
done.
No single control measure will ensure protection from
Phytophthora.
Several approaches must be directed at preventing the
introduction and spread of these fungi and at
preventing conditions favorable for disease
development.
These approaches include proper establishment and
production practices, disease resistance and chemical
control
Fusarium Stem Rot - Dieffenbachia
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Caused by Fusarium solani
Infection takes place at the soil line
This is followed by the production of a
brown spot.
As the tissue dies, it becomes tan and
falls away, removing tissue from the edge
to the heavy center vein tissue
Fusarium Stem Rot - Dieffenbachia
Fusarium Wilt
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Caused by Fusarium solani
Infection takes place in the roots
Lower leaves turn yellow and wilt, followed by
overall plant wilting and death of entire plant.
Lower portion of stem near soil line turns dark
brown-to-black with brown discoloration in
vascular tissues.
Fusarium Wilt Chrysanthemum
Fusarium Wilt Chrysanthemum
Fusarium Wilt -Tip Necrosis of
lisianthus
Fusarium Wilt -Tip Necrosis of
lisianthus
Management
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Planting disease-free cuttings,
sterilization of potting soil and benches
offer best means of control.
Do not injure plants at the soil line.
Apply iprodione (Kidon, Rovral, Chipco 26019) or
etridiazole (Truban, Terrazole) + Thiophanatemethyl (Banrot) to protect healthy plants.
Anthracnose and brown leaf spot
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Caused by (Colletotrichum spp. or
Leptosphaeria spp.)
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Occur throughout the world in
greenhouse and indoor landscapes.
Symptoms/Signs
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Symptoms of two leaf spots are very similar, with
both occurring primarily during the cooler, winter
months.
Leaf spots are initially tan and water-soaked and
may have a bright yellow halo.
Fruiting bodies of the causal organism (Glomerella
or Colletotrichum spp. [anthracnose]) or
Leptosphaeria sp. (brown leaf spot) appear in
concentric rings of tiny black specks within the
leaf spot.
Colletotrichum Dieffenbachia
Colletotrichum - cyclamen
Colletotrichum -cyclamen
Control 
Keep foliage dry, and protect from cold
water drips due to condensation on overhead
structures.