Common diseases and disorders of Aglaonema

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


Bacterial blights and stem rots
Pathogen - Erwinia carotovora subsp. carotovora or E. chrysanthemi
Symptoms - Bacterial blight is typified by watery leaf spots with centers that fall out. Bacterial stem rots caused by Erwinia spp. are generally first noticed when cuttings are stuck. The cut end of the stem becomes mushy and foul smelling and the rooting process stopped. The leaves on infected cuttings usually yellow quickly.
Control - Control of bacterial leaf spots or blights can be best accomplished through use of clean propagation material and a watering system that either does not wet the foliage or allows it to dry rapidly. Both antibiotic and copper compounds provide little control of bacterial diseases and are not recommended. Bacterial stem rot is usually not possible to control once started. Use of clean cuttings is the only successful method of cultural control although some growers have reported dipping in Agri-Strep as a moderately successful control method.

Xanthomonas leaf spot
Pathogen - Xanthomonas campestris pv. dieffenbachiae
Symptoms - Reddish-brown areas with bright yellow margins form on leaf edges are the most common symptom. Under wet and warm conditions, bacteria also spread into leaf centers and lesions expand until they reach a leaf vein.
Control - Minimize water on leaves and use clean cuttings. Sprays of copper or antibiotic compounds on a weekly basis provide moderate control under some growing conditions. Be careful to use appropriate rates of copper compounds since copper toxicity symptoms look similar to those caused by the bacteria.

Fusarium stem rot
Pathogen - Fusarium solani or F. oxysporum
Symptoms - Fusarium stem rot appears as a soft, mushy rot at the base of a cutting or rooted plant. The rotten area frequently has a purplish or reddish edge. Fusarium spp. sometimes form tiny, bright red, globular structures (fruiting bodies) at the stem base.
Control - Thiophanate methyl compounds (Domain, Cleary's 3336, Systec, Fungo, Topsin M) are labeled and should control Fusarium stem rot. Treat cuttings with a dip or a post-sticking drench to control losses. Remove infected plants from stock areas as soon as they are detected. Since Fusarium stem rot appears similar to Erwinia blight, accurate disease diagnosis is very important prior to applications of pesticides.

Myrothecium leaf spot
Pathogen - Myrothecium roridum
Symptoms - Leaf spots are generally found at wounds, although it is common to find no obvious wound and very large (up to 1 inch) leaf spots. The spots are usually tan to brown and may have a bright yellow border. Black and white fruiting bodies of the pathogen form in concentric rings on the leaf underside.
Control - Keep plant leaves as dry as possible and avoid excessive handling. Although both chlorothalonil (Daconil 2787) and mancozeb (Manzate 200 80WP) provide good control, they are not labeled on aglaonema for this disease.

Pathogen - Colletotrichum spp.
Symptoms - Leaf spots are initially tan and water-soaked and may have a bright yellow halo. Fruiting bodies of Collectotrichum spp. appear in concentric rings of tiny black specks on the upper surface.
Control - Keep foliage dry, and protect from cold water drips due to condensation on overhead structures. Many fungicides, such as mancozeb (Manzate 200DF), iprodione (Chipco 26019 50WP) or thiophanate methyl compounds (see Fusarium listing above) are effective but may not be labeled for aglaonema.

Dasheen mosaic
Pathogen - Dasheen mosaic virus (DMV)
Symptoms - Dasheen mosaic virus is rarely seen on aglaonema but symptoms can include mosaic, leaf distortion and stunting.
Control - DMV can be spread by both aphids but more commonly. It is very important to use pathogen-free stock since the symptoms of DMV are not always noticeable. No chemicals have any known effects on this virus disease.


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