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Alternaria
leaf spot
Pathogen - Alternaria spp.
Symptoms - Alternaria leaf spot of Salvia spp. (usually found
on blue salvia) is characterized by small spots which are initially
water-soaked. These spots turn reddish-brown or black, may reach
1/8 inch in diameter and are roughly circular. Spots generally do
not merge but severe infections readily cause leaf drop, especially
in the landscape.
Control - Alternaria leaf spot can be controlled through
a variety of methods. Although impractical in the landscape, elimination
of water on leaves can control Alternaria leaf spot. Chlorothalonil
(Daconil 2787), mancozeb (Dithane T & O), and iprodione (Chipco
26019) are effective for controlling this disease but you should
check labels for legal uses on Salvia. Check transplants for spots
before planting them in the landscape. |
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Botrytis
blight
Pathogen - Botrytis cinerea
Symptoms - Infection of older flowers is quite common on
some species of Salvia. Leaf spot usually form at wound sites or
adjacent to blighted flowers. A small, water-soaked spot can rapidly
enlarge and cover the entire leaf or cluster of flowers. Sporulation
on necrotic leaves or flowers appears as a powdery grayish-green
mass.
Control - Watch for Botrytis when the following conditions
occur - low light, high humidity, poor air circulation and warm
days with cool nights. Fungicides such as vinclozolin (Ornalin 50WP)
and iprodione (Chipco 26019 50WP) are effective against botrytis
blight on many plants. |
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Corynespora
leaf spot and stem rot
Pathogen - Corynespora cassiicola
Symptoms - This disease has most commonly been found on Salvia
splendens cultivars. Small black spots form on leaves when plants
are no more than an inch tall. Leaf spots can enlarge to 1/4 inch
wide and sometimes have a bright yellow halo surrounding the black
center. At this stage the disease can also cause damping-off due
to stem rot at the potting medium surface. Stem rot can occur on
plants up to 12 inches tall in 6 inch pots. The rotted areas are
usually within 3 inches of the potting medium and can be covered
with the black spores of the fungus.
Control - Reduce overhead irrigation and exposure to rainfall
to diminish spread of spores. Some cultivars are very susceptible
to stem rot and damping-off such as `Empire Lilac' and `Empire Light
Salmon'. Other cultivars are more susceptible to the leaf spot phase
of the disease (`Red Hot Sally'). `Fuego' was found to be the most
resistant cultivar tested. Good control with mancozeb (Dithane T
& O) and chlorothalonil (Daconil 2878) have been reported for
this disease on other ornamentals. At this time, iprodione (Chipco
26019) is the only fungicide registered for use on salvias in Florida
which could give good control of this disease. Be sure to test all
fungicides for safety before broad scale use on your crops and follow
labels for rates and intervals. |
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Desiccation
Pathogen - Lack of water
Symptoms - Salvia develop marginal burning. Wilting may or
may not be present. In severe cases of desiccation the plant may
wilt and die. In less severe cases, chronic lack of water will slow
the growth rate and flower production.
Control - Salvia should be watered consistently to avoid
development of marginal burning. Increase irrigation to supply sufficient
water and monitor more carefully. |
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Macrophomina
stem rot
Pathogen- Macrophomina phaseolina
Symptoms - Stem rot can occur on plants (generally Salvia
splendens cultivars) in the landscape up to 12 inches tall. The
rotted areas are usually within 3 inches of the soil but can also
occur at the top of the plants during the summer when rain splashes
the spores into the upper foliage. These stem cankers are dryish
and turn black with the black spores of the fungus, thus giving
the disease is common name of charcoal rot.
Control - Control of this disease is difficult once it becomes
established in a planting bed. It may be necessary to heat treat
the soil using plastic mulch during the summer. Leave the plastic
on the bed as long as possible to kill the fungus. This treatment
will also kill weeds and other fungi that may be present. If the
problem persists try growing a different bedding plant the next
season. |
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Powdery
mildew
Pathogen-Oidium sp.
Symptoms - Spots of frosty white growth appear on leaves.
The powdery coating can form up to 1/2 inch circular areas as single
spots or can join to cover the entire leaf. Most spots are found
on leaf undersides. The disease is most common during the drier
periods of the year and has been found on both blue salvia and S.
splendens cultivars.
Control - The disease apparently does not cause serious losses
although I have seen it in every area of the country where salvia
is grown. Dodemorph (Milban 39EC) is effective but labels must be
checked for appropriate and legal use on Salvia. |
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Pseudomonas
leaf spot
Pathogen - Pseudomonas cichorii and sometimes P. syringae
Symptoms - Spots are water-soaked and turn tan to black.
They may have a yellow edge but this is not common. In severe cases,
leaf drop is common. The disease has been found on all salvia species.
Control - Always examine new plants carefully for tan of
black spots on the basal leaves. Avoid overhead watering as much
as possible to reduce conditions for infection and spread of the
pathogen. Preventive applications of a copper bactericide may aid
in disease control but generally are not completely effective. Keep
in mind that many other bedding plants (coreopsis and purple coneflower)
are susceptible to the same bacteria and spread to adjacent plants
is common. |
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Rust
Pathogen - Puccinia farinacea var. azurea
Symptoms - Rust disease is most common on the blue salvia
and is easily recognized because of the reddish-brown pustules
which occur on leaf undersides. The spots first appear white or
light yellow when viewed from the upper surface. Most rust pustules
form on the undersides of leaves but some can be found on leaf
upper sides as well as petioles and stems.
Control - Rust diseases are inhibited by frequent rainfall
or irrigation and high temperatures. Fungicides for rust control
include chlorothalonil (Daconil 2787), ferbam (Carbamate), triadimefon
(Bayleton) and mancozeb (Dithane M-45 and Fore).
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