Caladium Diseases
The most common diseases are Fusarium and Pythium. The main symptom is root rot. Use fungicides such as Medallion to control Fusarium and Subdue to control Pythium. A fungicide drench should be applied 1-2 weeks after planting to control these fungal pathogens. Alternatively, a number of effective fungicides are now available in granular form and therefore may be incorporated in potting soil.
Stunted Growth:
Make sure that bulbs are not stored at temperatures below 60°F (16°C), or above 90° (32°C). Injury due to temperature exposure manifests itself in stunted (sometimes very slow) erratic growth even though the bulb does not show any injury at all.
Sunburn:
White and pink cultivars that have been grown during cloudy, early spring days and are suddenly exposed to high light intensity might show brown blotches on the leaves. Additional shade will stop this problem. Not necessarily a “disease”.
Leaf Spots:
A bacterial leaf spot may occur that is caused by a bacterial pathogen known as Xanthomonas. To prevent damage due to Xanthomonas, be sure plants are well spaced, that there is plenty of air circulation and keep the foliage dry. The bactericide Agrastrep, can be a useful spray material but the cultural controls listed above are best. Nutrient imbalances may cause leaf spots (Ca and K esp.) A pH higher than 7.0 is also known to cause brown spots.
Other Foliage Problems:
Pink areas in white cultivars like White Christmas of Jackie Suthers usually are a stress related symptom. High temperatures (>100°F) can induce this symptom. If you can cool off your crop this problem should disappear in newly emerging leaves if it has been caused by high temperature.
Light Intensity:
Caladiums can be forced under a wide range of light intensities. Thirty percent shade (achieving light levels of 2500 to 5000 foot candles or greater) seems to be acceptable. In northern areas, it may be possible to produce caladiums under 0-20% shade, since light intensity is not as high as in the south. Spacing can also affect light available to the plant. Since Caladiums have such a short crop time, it is wise to space them as soon as they sprout. Many growers space them at planting.
Fertilization:
Although many growers do not fertilize, we recommend:
50-100 PPM N (constant) of 6-6-6 or 20-20-20 or
300 PPM N (weekly) with fresh water in between
Insect Control:
Caladiums are rarely damaged by insects or related pests. But a good pest-monitoring program together with Orthene is recommended for the control of aphids. A general all-purpose insecticide is usually sufficient