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
 

	Aspergillus corm rot 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 be discarded. 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.
	Botrytis blight 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 disease. 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.
	Dasheen mosaic 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.
	Fusarium tuber rot 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.
	Rhizoctonia aerial blight 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.
	Xanthomonas leaf spot 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.

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