Common diseases and disorders of Pellionia, Pilea and Fittonia

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.
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Bidens mottle on Fittonia
Pathogen - Bidens Mottle Virus
Symptoms - Distortion of the normally symmetrical leaves is the most common symptom of this viral disease. Yellowing between veins and stunting can occur on severely infected plants. The disease appears to be most severe during the cooler periods of the year. This disease has rarely been seen on fittonias during the past ten years.
Control - This virus is transmitted from common weed hosts to the fittonia via aphid vectors. Remove weeds from around greenhouses as much as possible and keep aphid populations under control. Once plants are infected they should be removed and destroyed since they will not recover from the infection even if they don't show symptoms on a continuous basis.

Chilling injury on Fittonia
Pathogen - Air temperatures below 45 or 50F
Symptoms - Youngest leaves are most sensitive to chilling injury and develop white to tan splotches, especially near leaf edges. Exposure to 50F will cause leaf burning but will not result in wilt and tip damage. Leaf wilt and flower collapse occur if nerve plants are exposed to temperatures below 45F for extended periods of time.
Control - Keep production air temperatures at least 55F. The damage is permanent, but plants will produce healthy leaves when air temperatures are adequate, unless the shoot tip has been damaged by extreme cold for extended periods.

Edema of Pilea cadierei
Pathogen - Cool air temperatures with excess soil moisture
Symptoms - Leaves develop a warty appearance, especially near edges. These raised areas are easiest to see on undersides of leaves and may be slightly water-soaked or tan.
Control - Be careful to control the amount of water supplied to plants when the air temperatures are unseasonably cool.

Rhizoctonia aerial blight
Pathogen - Rhizoctonia solani
Symptoms - Discrete spots form all over plant foliage. The web-like mycelium of the fungus is usually reddish-brown or tan and can cover any part of the plant. Infected leaves wilt and die rapidly.
Control - Cultural controls for Rhizoctonia aerial blight are the same as for any soil-borne fungus. Do not reuse pots without thorough cleaning and never reuse soil from infected plants that have died. Grow plants away from the ground and avoid overwatering, which stresses the plant and allows the pathogen to attack more easily. Chemical control of this disease can be achieved with applications of thiophanate methyl (Cleary 3336, Domain and others) which are labelled for ornamental crops. Be sure to check labels for legal use rates and intervals prior to application.

Xanthomonas leaf spots on Fittonia, Pilea and Pellionia
Pathogen - Xanthomonas campestris
Symptoms - Symptoms on aluminum plant (Pilea cadierei) are dry, tan, irregularly shaped spots found primarily in the white areas of the leaves. Spots on other pileas tend to be dark brown to black and may be angular in shape since they rarely spread across leaf veins. Symptoms on pellionias are dryish, irregularly shaped spots with a corky, slightly raised border found mainly on leaf undersides. Hosts include aluminum plant, creeping Charley, Pilea spruceana, Pilea invulcrata (silver tree), satin pellionia, and trailing watermelon begonia. Creeping Charley and satin pellionia were most susceptible, while trailing watermelon begonia was relatively resistant.
Fittonias are commonly infected with a similar but distinct bacterium which cannot infect pileas or pellionias. Most producers do not recognize the symptoms as a disease problem since edge burning and vein blackening are the most common symptoms. These are sometimes confused with irrigation, phytotoxicity, or temperature problems. All types of fittonias have been found to be susceptible to this pathogen, as were some related plants such as Aphelandra squarrosa (zebra plant).
Control - Chemical control of both bacterial diseases is rarely successful and cultural methods should be the first line of defense. Fittonias are especially sensitive to streptomycin sulfate and copper compounds; disease severity actually increases when these compounds are used on fittonias infected with Xanthomonas sp. Elimination of overhead watering and/or exposure to rainfall aid in control of disease development and spread. However, once infection occurs, lesions can expand even when leaves are kept dry. Discard all plants infected with this pathogen and never use infected plants for stock, since the disease is easily carried on tissue even though no symptoms are evident. Unfortunately, plants with the highest quality were found most susceptible to this disease in fertilizer trials. Other plants susceptible to the Xanthomonas sp. from Pilea and Pellionia spp. include many Ficus spp. and bird-of-paradise (Strelitzia).


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