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record of the Institute for Food and
Agricultural Sciences and should be
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Copyright 2005, Board of Trustees, University
// CALADIUM DISEASE CONTROL
J. F. Knauss and R. O. Magie'
University of Florida, IFAS ..
Apopka ARC Research Report RH7T5
I. TUBER ROT PATHOGENS /
A. Bacterial U 1976
Erwinia carotovora A S
Erninia chrysan-themi F"l-o Oridaj
Fusarium solani, Fusarium spp.
S Pythium nyriotylum, Pythium spp.
For planting stock, always select the healthiest tubers harvested from the
previous year's crop. The pathogens mentioned above survive from one season
to the next on infected tubers and selection of the best tubers (those which
appear the healthiest) for planting stock will keep the initial pathogen
population introduced into the planting area low. This is important because
low pathogen numbers early in caladium field culture usually aids in reducing
disease development throughout the growing season. Heat treatment of the
Associate Professor, ARC-Apopka and Professor, AREC-Bradenton, respectively.
2The authors thank Dr. Frank Marousky, AREC-Bradenton, for his suggestions
regarding the proper curing conditions for caladium bulbs.
planting stock at 1220F for 30 min, prior to cutting into planting chips is essential
in caladium culture and may be the difference between success or failure of the crop.
In research experiments, Benlate 50 WP (1.5 lb/100 gal) and streptomycin (200 ppm) have
been added to the heated treatment water with no adverse effect on their activity.
Both might be tried on a limited basis to a portion of the planting stock to further
evaluate their effectiveness when used in this manner. Proper heat treatment of planting
stock will eliminate Pythium and Phytophthora and possibly a portion of the other fungal
pathogens prior to chipping, dusting and subsequent planting. Heat-treated tubers are
much less likely to initiate disease through introduction of pathogens into the planting
area or in the planting chips. In tuber heat treatment, it is essential that the
temperature is maintained as close to 122F as possible and not be allowed to exceed
is temperature during the 30 min. treatment period. Constant observation of the
thermometers during the heat treatment process is important and worth every minute spent.
After the 30 min. heat treatment, extract the tubers and cool immediately ip clean
tap water**. After cooling, allow the tubers to dry in a clean area before cutting
into chips. Do not place these heat-treated tubers where they may become recontaminated
with caladium pathogens before chipping and planting. If you are heat treating for the
first time, do not be alarmed if after planting, the pieces seem a little slow in
germinating. Heat treatment has been shown to delay germination for approximately
7-10 days with no adverse effect upon later growth and bulb production. After heat
treatment and cutting the tubers, immediately apply a fungicide--bactericide dust.
Dusts which have been successfully employed on chips are:
SCaptan (5%) + Benlate (2.5%)
Captan (50) + Benlate (2.5%) + Streptomycin (0.5%)
Add streptomycin (200 ppm/100 gal water) to cooling water.
All these dusts are given in percentage of active ingredient.
In fall, after digging, wash tubers thoroughly and spray with or dip in a solution
containing 3 lb of Captan plus 200 ppm streptomycin/100 gal of water. Benlate 50 WP
might also be included in the spray or dip at l4 lb/100 gal. Ten percent Botran or
Difolatan dusts have also been reported as satisfactory in controlling storage rots
After digging, washing and chemically treating, tubers should be dried thoroughly
with fans. For curing, tubers are held at 80-900F for 10 days to 2 weeks. These
temperatures are helpful in developing a coating of suberin over the wounded areas.
Suberin is the chalky-white scar tissue which forms over injured surfaces. The suberin
layer protects against excessive drying and against' disease development. After tubers
cured, they should be stored at a controlled temperature of 700F. In the event
controlled temperature storage is not available, tubers may be stored at ambient
temperatures but the temperature should not be allowed to go below 700F for prolonged
periods. Caladiums are cold sensitive and are injured when exposed to low temperatures
(40-60F). Injury can vary from slight inhibition of growth to death. Death by cold
injury (40F for 6 days) can easily be mistaken for rotting by a disease organism.
II. PATHOGENS AFFECTING PLANTS IN FIELD
Pythium yriotylum, Pythium spp.
S Phytophthora spp.
Fusarium solani, Fusarium spp.
Prepare the planting area properly for fumigation. Grade the soil in a manner that
allows the boundary areas to slope away from the area to be planted. Make certain the
drainage ditches are large enough to handle all anticipated run-off from the field.
These practices will help prevent wash-ins into the treated area and help to prevent its
recontamination. Fumigate the planting area, including road and turn areas. Plant
dusted chips obtained only from healthy heat-treated tubers. The following information
on field application of fungicides is to be taken as preliminary and is based upon
research conducted since 1972 and on results obtained from research conducted on
ornamental foliage plants. This research is continuing so that within the coming years
specific recommendations can be made based on thorough research results. At present,
it is felt that in-row spray treatments in the planting furrow at planting time, coupled
Pth 2 or more band treatments at the base of the plants during the growing season may
provide assistance in keeping the root and crown decay pathogens of caladiums under
control. The following fungicides and their stated concentrations on a 100 gal water
basis have given safe and effective control of the caladium pathogens listed:
Truban 30 WP (12 oz)
Terraclor 75 WP (1 ib)
Fermate 76 WP (2 Ib)
Demosan 65 WP (1 Ib)
Benlate 50 WP (12-16 oz)
S Terraclor 75 WP (1 ib)
Fermate 76 WP (2 Ib)
In the tropical foliage industry, Truban has been combined with either Benlate,
Fernate or Terraclor to produce a wide-spectrum soil fungicide. Benlate should never
be used alone as an in-row or band spray treatment and should always be used in
combination with Truban. The normal rate of application for these soil fungicides is
1 pint/sq ft or 1 pint/each 3 feet of a 4 inch band or in-row treatment. To cut down
on the amount of fungicide suspension needed, it is safe to increase the fungicide
concentration by puttingthe same amount in 25 gal water and applying pint/sq ft or
4 pint per each 3 feet of 4 inch band or in-row treatment. Although even higher
fungicide concentrations and corresponding lower application rates might be used, they
are not suggested because research has not yet determined their safety to caladiums.
Follow the chemical band applications with to 1 inch of irrigation water. One
optionn to applying the fungicides at a 4X concentration and following the chemical
band application with to 1 inch of irrigation water would be when either Sclerotium
rolfsii or Rhizoctonia are visibly attacking the basal portion of the leaves at the
soil line. In this case, the normal concentration of the fungicide stated on Page 4
should be used and the band application should only be followed with a light watering
to wash the chemicals from the upper foliage. Whenever possible, all the proceeding
chemical band applications should be done in the cooler morning hours, with the later
afternoon and evening hours as a second choice.
FUNGICIDES AND THEIR CONCENTRATION REPORTED IN THIS HANDOUT ARE NOT TO BE TAKEN AS
FOLLOW LABEL RECOMMENDATIONS IN USE.