Common diseases and disorders of Salvia

A.R. Chase is a Plant Pathologist and President of Chase Research Gardens, Inc.
C.R.G. is a private research and consulting corporation specializing in ornamental plants.
Both hourly and contract services are available.
You can reach C.R.G. at P.O. Box 168, Mt. Aukum, CA 95656 Phone and Fax: 916-620-1624 - E-mail: MTAUKUM@AOL.COM


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.

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.

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.

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.

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.
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.
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.


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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