is a Plant Pathologist and President of Chase Research Gardens, Inc.
C.R.G. is a private research and consulting corporation specializing in
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
Pathogen - Aspergillus niger
Symptoms - The pathogen is most commonly found on wounded
or damaged tissues. Since the process of digging caladium tubers
can result in wounded tubes, Aspergillus can sometimes be a problem.
Small, sunken brown rotted areas associate with wounds form. Under
warm conditions, the fungus sporulates giving the tuber a fuzzy
black covering. The spores are easy to see with the naked eye and
are slightly larger than pepper grains. It is not uncommon for other
pathogens such as Fusarium spp. to be present as well. In some cases,
the tubers can still generate a vigorous plants but in others the
tuber is so weakened that it cannot produce a good plant and should
Control - Pre-storage dips or dusts of the tubers should
aid ion control of this tuber rot. The combination product of thiophanate
methyl and etridiazole (Banrot) may aid in control of some of the
fungi causing tuber rots of caladium. Hot water treatment (about
122°F) can aid in control of some fungi that rot caladium tubers.
Be sure to test the effect of temperature on the viability of the
caladium before attempting broad scale use. In addition, store tubers
at 70°F. Storage at higher temperatures will allow the pathogens
to develop while lower temperatures can result in damage to the
tuber which in turn weakens it defense against tuber rotting fungi.
Pathogen - Botrytis cinerea
Symptoms - Tan to brown spots can form on leaves and petioles
and under severe conditions all of the leaves may be infected and
result in complete melting down of the plant. Botrytis blight occurs
primarily during the cool, wet and cloudy times of the year especially
during the winter or early spring. Reducing the relative humidity
by plant spacing, watering by a method that does not wet the foliage
and venting and heating the greenhouse late in the day will each
reduce the conditions that favor development and spread of this
Control - Chlorothalonil in a fogger form (Exotherm Termil)
is registered for this use on caladium. Iprodione (Chipco 26019
50WP) provides excellent control of Botrytis blight on many crops.
Pathogen - Dasheen mosaic virus (DMV)
Symptoms - Dasheen mosaic virus can be severe when infected
plants are used to grow tubers. The resulting crops will each be
infected with the virus and tuber size and numbers will be reduced
compared to virus-free crops. Symptoms include mosaic, leaf distortion
and stunting, and appear periodically during the year depending
upon the environmental conditions.
Control -DMV is sometimes spread by aphids and they should
be strictly controlled during tuber production. It is very important
to use pathogen-free stock whenever possible since the symptoms
of DMV are not always noticeable. No chemicals have any known effects
on this virus disease. Other hosts of this virus include dieffenbachia,
philodendron, taro and anthurium.
Pathogen - Fusarium solani
Symptoms - Fusarium tuber rot occur initially on the new
tubers as small sunken areas (Top). In advanced infections the tubers
are completely rotted with a dry, chalky texture. The spores of
the pathogen may form and are yellow to tan in color. If tubers
with Fusarium are planted the resulting plants will be stunted and
of poor quality (Bottom)
Control - Use the same controls as mentioned for Aspergillus
tuber rot. Fungicides such as chlorothalonil (Daconil 2787), thiophanate
methyl (Domain or Cleary's 3336), and mancozeb (Dithane M-45) provide
excellent control Fusarium diseases of other ornamentals.
Pathogen - Rhizoctonia solani
Symptoms - Rhizoctonia aerial blight occurs primarily during
the summer or warmer months. Disease development can occur in less
than a week, so plants should be checked carefully and frequently.
Brown irregularly shaped spots form anywhere in the foliage, but
most commonly within the crown of the plant which is often wet.
Sometimes the first symptoms form near the top of plant confusing
the source of the disease (the soil). The disease spreads rapidly
and the entire plant can become covered with the brown weblike mycelium
of the pathogen.
Control - A pathogen-free potting medium is the first step
to control of all soil borne pathogens such as Pythium and Rhizoctonia.
Plants should be produced from pathogen-free stock and grown in
new or sterilized pots on raised benches. Since this pathogen inhabits
the soil both the roots and the foliage of the plants must be treated
with a fungicide to provide optimal disease control. A combination
drench -spray will best accomplish this. Chlorothalonil (Daconil
2787 or Exotherm Termil), iprodione (Chipco 26019), and thiophanate
methyl (Domain and Cleary's 3336) are each effective in controlling
this disease on other tropical ornamentals. Check labels for legal
uses on caladiums.
Pathogen - Xanthomonas campestris pv. dieffenbachiae
Symptoms - Leaf spot on caladium starts as tiny water-soaked areas
which can rapidly enlarge to 1/4 inch or more. They tend to form
on leaf margins but when the bacterium infects a major leaf vein
the entire leaf can collapse. Spots are frequently very black and
surrounded by a bright yellow halo. Most other plants in the Aroid
family such as Aglaonema, Anthurium, Dieffenbachia and Syngonium
are also hosts of this pathogen.
Control -Eliminate all stock plants which have Xanthomonas leaf
spot. All bacterial diseases are very difficult to control unless
plants are grown without overhead watering or exposure to rainfall.
Bactericides such as copper containing compounds may be somewhat
effective if used on a preventative and regular basis.