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 Physiological problems
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 Fungal pathogens
 Major insect and mite pests
 Reference






Group Title: ARC-A foliage plant research note - Agricultural Research and Education Center - RH-84-A
Title: Croton
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00066546/00001
 Material Information
Title: Croton
Series Title: ARC-A foliage plant research note
Physical Description: 6 p. : ; 28 cm.
Language: English
Creator: Osborne, L. S
Chase, A. R ( Ann Renee )
Conover, Charles Albert, 1934-
Agricultural Research Center (Apopka, Fla.)
Publisher: University of Florida, IFAS, Agricultural Research Center-Apopka
Place of Publication: Apopka FL
Publication Date: 1984
 Subjects
Subject: Croton (Genus) -- Growth -- Florida   ( lcsh )
Croton (Genus) -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 5).
Statement of Responsibility: L.S. Osborne, A.R. Chase, and C.A. Conover.
General Note: Caption title.
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00066546
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 71314739

Table of Contents
    Copyright
        Copyright
    Physiological problems
        Page 1
    Diseases and bacterial pathogens
        Page 2
    Fungal pathogens
        Page 3
    Major insect and mite pests
        Page 4
    Reference
        Page 5
        Page 6
Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida







CROTON

L. S. Osborne, A. R. Chase and C. A. Conover

University of Florida, IFAS
Agricultural Research Center Apopka
ARC-A Foliage Plant Research Note RH-1984-A

Crotons have been popular in tropical gardens for centuries, but only
in recent years have they become popular indoor plants. Even the most
popular croton cultivars commonly available in the U. S. through the early
1970s, such as Codiaeum variegatum 'Bravo' and 'Oakleaf' experienced con-
siderable leafdrop upon placement in an interior environment. During the
last 5 to 10 years, many new varieties have been developed in Europe which
tolerate low light interior conditions. Considerable research has been
conducted under European greenhouse conditions on these cultivars, including
stock production, propagation, and factors affecting growth of pot plants,
but has little application in Florida since it was conducted under light
intensities and temperatures that are much lower than those found in Florida
except for winter periods.

Croton cultivars grown in Florida for interior use include Codiaeum
variegatum 'Bravo', 'Elaine', 'Gold Dust', 'Norma', and 'Petra'. Many other
European cultivars bred for interior use are available, but are not widely
used in the U. S. marketplace. Most American cultivars have been selected
for landscape use and defoliate excessively under interior conditions.
Potted plant production light levels suggested for the cultivars mentioned
above should be in the range of 3000 to 5000 ft-c or higher. Light levels
as high as 6000 to 7000 ft-c are acceptable provided temperatures can be
controlled. These light levels can be obtained with 30 to 63% shade cloth
depending on season. Excellent growth can be obtained with 3-1-2 N-P-K
ratio liquid or slow release fertilizer when applied at a rate of 1500 to
2100 lb N/A-yr (equivalent to 34 to 48 lb N/1000 ft /yr) plus micronutrients.
The lower rate is applicable to lowest light levels and the higher rate to
highest light levels. Potting media used for crotons should have good
aeration, but not be excessively drained since crotons wilt rapidly if
allowed to dry. Crotons tolerate 40 to 1000F without chilling or heat
damage for short periods, but best growth and quality occur between 65 and
900F.

PHYSIOLOGICAL PROBLEMS

1) Poor color development

Symptoms Terminal leaves are mostly green and even after they mature,
color intensity is poor or uneven.

Control Best color develops in bright light under cooler temperatures.
Therefore, it is more difficult to obtain good color in summer than
other times of the year. In summer, color improvement can be


Assistant Professor of Entomology, Associate Professor of Plant Pathology
and Professor, Horticulturist and Center Director, Agricultural Research
Center, 2807 Binion Road, Apopka, FL 32703.






obtained with higher light, cooler temperatures and sometimes
reduced fertilizer levels. Winter color is rarely a problem
provided proper light is provided and fertilizer rate is not
excessive.

2) Faded foliage (phototoxidation)

Symptoms Subterminal leaves become dull and grayish where flat
surfaces face the sun during the hottest part of the day. This
occurs primarily when plants are grown in summer in full sun or
under light shade with high temperature.

Control Increase shade level or ventilate to reduce leaf temperature
to reduce fading.

3) Excess fertilization

Symptoms Leaf blades roll and some entire leaves may twist and
reduce aesthetic value of plants. Rolling is often also present
when leaf size is large and color poor.

Control The symptom is most commonly present when plants receive
excess fertilizer and are growing rapidly under low light levels.
Reduce fertilizer level and increase light intensity.

DISEASES
Croton are subject to a variety of bacterial and fungal diseases.
Leaf spots, root rots and stem galls are the most common symptoms of these
diseases. Stem galls are caused by both fungi and bacteria and can be
avoided by strict adherence to a sanitation program. Leaf spots are best
controlled through avoiding wet leaves and root rots are always easiest
controlled when using sterilized potting media and pots. Although croton
are known to be susceptible to disease, they are freer of these problems
than many other foliage plants.

BACTERIAL PATHOGENS
1) Crown gall (Agrobacterium tumefaciens)

Symptoms Slightly swollen areas on the stems, leaf veins and even
roots are initially apparent. These swollen areas enlarge and
become corky. In cases of severe infection they may enlarge and
merge to create a very distorted stem or root mass. Galls may
also form on the ends of cuttings or stems where cuttings have
been removed.

Control Remove and destroy all plants found infected with the
bacterium, then sterilize any cutting tools used on them. Since
a fungus is also known to cause galls on croton, an accurate
disease diagnosis must be made for all croton with gall symptoms.








FUNGAL PATHOGENS

1) Anthracnose (Colletotrichum sp. or Glomerella cingulata)

Symptoms Spots on all ages of leaves. Spots are initially water-
soaked and become tan with age. Tiny black fungal fruiting
bodies sometimes form in the dead tissue of the spot.

Control Avoid wet foliage since this is necessary for infection
and spread of spores. This is especially crucial during mist
propagation. Maneb compounds and chlorothalonil are effective
in controlling anthracnose on many foliage plants. Benomyl is
labeled for use on this crop and is also effective against
anthracnose.

2) Stem gall and canker (Kutilakesa pironii)

Symptoms Symptoms caused by this fungal pathogen are very similar
to those described for crown gall. Diagnosis of this gall
symptom must be made by a plant pathologist to assure accurate
control methods are chosen. Aphelandras are also hosts of this
fungal pathogen and symptoms should be monitored on these plants
as well.

Control Cultural controls are the same as listed for the crown
gall. Benomyl is labeled for use on this plant and should be
effective against this pathogen.


PHYTOTOXICITY OF FUNGICIDES ON CROTONS

Safe Unsafe

Banrot 40 WP Ornalin 50 WP

Benlate 50 WP Chipco 26019

Daconil 4.17 F

Fungo 50 WP

Maneb compounds


Pesticides were tested at recommended
rates and intervals







MAJOR INSECT AND MITE PESTS


The major arthropod pests of croton include mealybugs, mites, scales,
and thrips. Mealybug, mite, and scale infestations are typically the result
of bringing infested plant material into the greenhouse. Thrips have the
ability to fly and thus invade the greenhouse from weeds and other
infested plants outside. In the control section for each pest a few of the
many registered and effective pesticides will be listed. For a complete
listing, please consult the references at the end of this report.

1) Mealybugs

Symptoms Mealybugs appear as white cottony masses in leaf axils, on
the lower surfaces of leaves and on the roots. Honeydew and sooty
mold are often present, and infested plants become stunted and,
with severe infestations, plant parts begin to die.

Control Systemic materials are preferred. Examples of chemicals
which have systemic activity are: Cygon 2E, Disyston, Metasystox-R,
and Orthene. Dycarb or Ficam appears to be as effective as some of
the systemic materials. Control of root mealybugs is accomplished
with soil drenches with an insecticide. Diazinon and Vydate are
the only insecticides registered for this purpose but both can cause
some phytotoxicity. When pesticides are applied to the soil, care
must be taken to assure that the pots have good drainage and that
no saucers are attached, or phytotoxicity may result.

2) Mites

Symptoms Two-spotted spider mites are the major arthropod pest of
crotons. They are very small and go unnoticed until plants become
severely damaged. Damaged foliage begins to turn yellow or become
speckled due to the feeding of mites. This discoloration is
difficult to see in some varieties of croton because of the yellow
appearance of healthy leaves. Often the presence of this pest is
overlooked because the cast skins and webbing produced by this
mite are confused for dust on undersides of leaves.

Control Mites can be controlled with Mavrik, Pentac, or Vendex.
The critical point in any control program is thorough coverage
with the pesticide. The best control program is to minimize the
possibility of introducing mites into the growing area on
infested plant material.

3) Scales

Symptoms Infested plants become weakened or stunted and begin to
die. Scales can be found feeding on leaves, petioles, or stems.
Their shape, size, and color are variable and many are hard to
distinguish from the plant material on which they are feeding.

Control See Mealybugs







4) Thrips


Symptoms Infested leaves become curled or distorted, with silver-gray
scars or calloused areas where feeding has occurred.

Control Many materials are registered and effective at controlling
thrips.


PHYTOTOXICITY OF INSECTICIDES AND MITICIDES ON CROTONS

SAFE QUESTIONABLE UNSAFE

Bacillus thuringiensis Vydate EC Malathion EC
Di-Syston EC Malathion EC
Dursban EC + FC-435 Oil
Dylox LS Morestan WP
Enstar 5E Plictran WP
FC-435 Oil
Kelthane EC
Mavrik
Omite WP
Orthene SP
Pentac WP
Sevin WP
Temik G
Vendex

Pesticides were tested at recommended rates and intervals.

References

1. Chase, A. R. 1983. Phytotoxicity of some fungicides used on tropical
foliage plants. ARC-Apopka Research Report, RH-83-2.

2. Short, D. E. 1978. Phytotoxicity of insecticides and miticides to
foliage and woody ornamental plants. Extension Entomology Report #57.


3. Short, D. E., L. S. Osborne, and R. W. Henley. 1982.
and related arthropod management guide for commercial
woody plants in Florida. Extension Entomology Report


1982-83 Insect
foliage and
#52.


4. Simone, G. W. 1983. Fungicides for use on ornamentals 1983-84.
Extension Plant Pathology Circular 484-A.









Mention of a commercial or proprietary product or of a pesticide in this
paper does not constitute a recommendation by the authors, nor does it imply
registration under FIFRA as amended.

Pesticides should be applied according to label directions. Those
pesticides listed in the control sections for each disorder but not listed
in the phytotoxicity charts HAVE NOT been tested for plant safety at the
University of Florida.




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