Title: Florida plant disease management guide
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Permanent Link: http://ufdc.ufl.edu/UF00053871/00009
 Material Information
Title: Florida plant disease management guide
Alternate Title: Ornamentals and turf
Fruit and vegetables
General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques
Physical Description: v. : ; 28 cm.
Language: English
Creator: University of Florida -- Dept. of Plant Pathology
Florida Cooperative Extension Service
Publisher: The Extension
Place of Publication: Gainesville Fla
Frequency: annual
regular
 Subjects
Subject: Plant diseases -- Periodicals -- Florida   ( lcsh )
Pesticides -- Periodicals   ( lcsh )
 Notes
Statement of Responsibility: Plant Pathology Dept., University of Florida and Institute of Food and Agricultural Sciences, Florida Cooperative Extension, University of Florida.
Numbering Peculiarities: Issued in three volumes: v. 1, General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques; v. 2, Ornamentals and turf; v. 3, Fruit and vegetables.
General Note: Description based on: 1999-2000.
General Note: "SP-52"
 Record Information
Bibliographic ID: UF00053871
Volume ID: VID00009
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 44549741
lccn - 00229071
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Preceded by: Florida plant disease control guide

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PDMG-V3-37
U UNIVERSITY of
UF FLORIDA
IFAS Extension



2006 Florida Plant Disease Management Guide:

Crucifers1


Tim Momol, Richard Raid and Tom Kucharek2

Specific Common Diseases

Alternaria Leaf Spot (Alternaria brassicicola,
Alternaria brassicae, and A. raphani)

Symptoms: The disease first appears as small
dark brown or black spots on the leaves. As the spots
enlarge a definite zonation, or concentric rings,
becomes evident. As spores are produced, the spots,
especially in the center, become darker than other
areas of the spots. With development of numerous
spots, the leaves may turn yellow and die. Spots on
stems and leaf petioles are elongate and purple to
brown. The fungus produces numerous small brown
sunken spots on cauliflower heads. See Plant
Pathology Fact Sheet PP-34.

Cultural Controls: Use crop rotation. Plow
down old plant beds and harvested fields. Use a
fungicide seed treatment. Employ fungicide sprays
starting in the seed production system. Ship produce
at a 40-45 F. Purchase disease-free transplants. Wet
conditions facilitate disease development. See Plant
Pathology Fact Sheet No. 34.


Chemical Controls: See PPP-6.

Anthracnose (Colletotrichum higginsianum )

Symptoms: This disease occurs primarily on
turnip, mustard, and Chinese cabbage. Small dry
circular, gray to straw-colored leaf spots are
produced. On leaf petioles and stalks the spots are
sunken, elongated and gray to brown with black
border. Gray or light tan spots, somewhat sunken, are
produced on turnip roots.

Cultural Controls: Use crop rotation.

Chemical Controls: Apply fungicides if needed.
The use of fungicides to control Alternaria leaf spot
will also confer a measure of control on this disease.
See PPP-6.

Bacterial Leaf Spot (Pseudomonas cichorii)

Symptoms: Slightly sunken gray-brown to
dark-brown, round or oval spots up to about 1/4 inch
across. Spots may show concentric (target spot)
rings; these spots usually larger than plain spots.
Spots may coalesce into large ones. Disease occurs


1. This document is PDMG-V3-37, one of a series of the Department of Plant Pathology, 2006 Florida Plant Disease Management Guide, Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date revised: December 2005. Please visit the EDIS Web site at
http://edis.ifas.ufl.edu.
2. T. M. Momol, associate professor, Plant Pathology Department, North Florida REC--Quincy, FL; R. N. Raid, professor, Plant Pathology Department,
Everglades REC--Belle Glade, FL; T.A. Kucharek, professor, Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and
Agricultural Sciences, University of Florida, Gainesville, FL 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and
other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex,
sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry
Arrington, Dean






2006 Florida Plant Disease Management Guide: Crucifers 2


mainly on the wrapper leaves, but under favorable
conditions, may cause injury to inside leaves.

Cultural Controls: Practice crop rotation.
Disease is favored by overhead irrigation and poor
field drainage. Purchase disease-free transplants.

Black Rot (Xanthomonas campestris pv.
campestris)

Black Rot (Xanthomonas campestris pv.
campestris)

Symptoms: Areas of yellow and light brown with
a network of black veins develop in leaves of affected
plants. Often there are "V" shaped areas at the edges
of the leaves. Movement of the bacteria down the
leaf veins into the vascular tissue of the stem
produces the systemic stage of the disease. A cross
section of a diseased stem shows the damaged
vascular system in a circle around the central pith.
Bacteria move from this area into upper, uninjured
leaves.



Cultural Controls: To obtain control of black rot
disease, a complete package approach to control must
be followed. Omission of any one step in the control
procedure may result in negation of disease control
efforts.

1. Purchase certified, disease-free transplants.

2. Upon receipt of transplants, examine plants for
early black rot symptoms before, not after,
planting. Refuse payment on shipments with
potential transplant-bome black rot. Infested
shipments can be legally refused.

3. Do not locate seedbeds or field plantings on land
planted to any crucifer during the preceding 12
months.

4. The use of tolerant varieties can decrease disease
losses in the field especially when proper rotation
is impossible.

5. Use strict sanitation in the transplant production
areas and in productions fields.


6. Plow down old crop debris in field as soon as
possible after harvesting.

7. Do not establish cull piles on the farm.

8. See Plant Pathology Fact Sheet No. PP-13 for
total disease control program.

9. Hot water treatment of all cabbage seed is
suggested regardless of source. Hot water
treatment is as follows:

Treat seed at 1220 F.

Cabbage and brussels sprouts seed should be
treated for 25-35 minutes.

Broccoli, cauliflower, collards, Chinese
cabbage, kale, kohlrabi, rutabaga and turnips
should be treated for 18 minutes.

Retreat seed with a seed treatment fungicide
prior to planting.

Black Speck (unknown cause)

Symptoms: On cabbage harvested during the
winter months, numerous pin head-sized black specks
may appear on the leaves extending all the way to the
core. Usually they appear approximately one week
after harvest. These specks may occur on cabbage in
the field, particularly if harvest is delayed.

Cultural Controls: The exact cause of these
black specks is not fully understood, however, some
varieties and hybrids are much more susceptible than
others.

Cercospora Leaf Spot (Cercospora sp.)

Symptoms: Definite spots, which are circular to
angular, pale-green to light-brown, are found
commonly on turnips in Florida. This disease also
occurs in cabbage within transplant production
greenhouses.

Chemical Controls: See PPP-6.






2006 Florida Plant Disease Management Guide: Crucifers 3


Damping-Off (Fusarium spp., Pythium spp.,
and Rhizoctonia spp.)

Symptoms: Failure of plants to emerge often
indicates pre-emergence damping-off.
Post-emergence symptoms show a water-soaked,
collapsed area in the stem below or near the soil
surface. Later the darkened, shrunken stem cannot
support the seedling and it wilts, falls over and dies.
Damped-off plants often are in circular areas or
extend some distance in rows.

Cultural Controls: Use seed treated with an
approved fungicide. Use healthy transplants. The field
should be free of old crop and weed debris in the soul
surface. See Plant Pathology Fact Sheets No. 1 and
53, and Circular 1025.

Chemical Controls: See PPP-6.

Downy Mildew (Peronospora parasitica)

Symptoms: All plant parts of crucifers can
become infected with this fungus. Leaf symptoms are
most commonly observed in Florida. Black or dark
specks appear on young leaves, usually on the
underside of the leaf first. Such spots are often
irregular in shape and may appear net-like. The upper
side of the leaf will also develop dark spots similar in
shape and may be accompanied by leaf yellowing. On
older leaves, coalescence of these spots can occur,
resulting in larger areas of the leaf blade having
large, sunken, paper tan-colored spots. Leaf
yellowing, again, may accompany these symptoms.
Early infection on young plants can cause stunting.
Disease is favored by cool wet weather.

On the underside of the leaf spots, a gray-white
downy growth can be observed with or without the
aid of a hand lens, especially when leaves are wet.
On mature cabbage, downy mildew can appear as
dark sunken spots on the head or wrapper leaves.
Often infections on the cabbage head will result in a
purplish tinge. Infections predispose the plant to soft
rot bacteria or Sclerotiniose, which can further rot
tissue in the field or after harvest.

Cauliflower curds and broccoli heads can
become infected with blackened areas on the outside
of the tissue. The infection can become systemic and


turn inner curd and stem tissue dark. Radish and
turnip "roots" can become infected from spores
that are washed down to the soil from the leaves.
Symptoms might predominate on the upper part of
the root but the entire root is susceptible. Black
spotting or a netted appearance can be observed on
the outside of the root but an internal, firm rot can
occur as well in some situations. Some root distortion
could occur, especially, if infection occurred early in
relation to root swelling. Flowers and weed stalks of
cruciferous crops, especially mustard, are also
infected.

Cultural Controls: Plow under abandoned
seedbeds and harvested fields to prevent diseases
from spreading to new plantings. Eradicate all
crucifers and weeds in vicinity of seedbed or
transplant production area. See Plant Pathology Fact
Sheet No. 33.

Chemical Controls: See PPP-6.

Sclerotinose (Sclerotinia sclerotiorum)

Symptoms: All parts of the plants are
susceptible. Infection occurs on leaves and stems
nearest the ground, or on the wrapper leaves in
cabbage. A small water-soaked spot appears and as it
enlarges, a growth of white mycelium is produced.
As the fungus grows upward on a maturing plant, it
often spreads over the head, darkening the leaves into
a soft, water-soaked mass. At this stage, numerous
black sclerotia (seed-like fungus reproductive
structures) 1/8 1 inch in length are produced on the
dead and dying parts. Where stems are heavily
infected, the plant wilts, falls over and dies. This
disease can follow cold temperature damage or other
injuries.

Cultural Controls: The following control
methods are recommended:

1. Rotate with a crop not susceptible to Sclerotinia
such as sweet corn.

2. Turn soil at least 6 inches deep when plowing.

3. Where possible, flood the soil either completely,
partially or intermittently for a period of 6 weeks
during the summer. Before using flooding as a

control measure, find out from local authorities if






2006 Florida Plant Disease Management Guide: Crucifers 4


drainage into a given body of water after
flooding fields is permissible.

4. The use of overhead irrigation may favor severe
disease incidence.

Chemical Controls: See PPP-6.

Turnip Mosaic (Turnip mosaic virus)

Symptoms: This disease (also known as black
ringspot) infects crucifers, beets, spinach, tobacco and
other plants and is transmitted by aphids. Plants
develop conspicuous symptoms between 75-85 F
and appear stunted with mottled leaves. The typical
mosaic symptom often develops first on the leaf
under surface as dark green spots which turn necrotic
forming a ring spot pattern. Symptoms on apparently
normal heads may develop in a post-harvest storage
situation.

Cultural Controls: Eliminate the natural weed
hosts of this virus (such as mustard type weeds) in
both seedbed and field situations. Early, rigorous
aphid control, especially in the seedbed, will reduce
subsequent virus incidence.

Wirestem (Rhizoctonia solani)

Symptoms: Roots (root rot), stems
(damping-off, wirestem), and leaves (bottom rot,
head rot) may be damaged by this fungus. One of the
most common types of damage is wirestem where the
outer tissues of the seedling stem shrivel, turn yellow
to orange to brown to black, and become tough and
woody. These tissues may slough off or, depending on
weather conditions, the seedling may recover. If
growth of the fungus continues up the stem, the
bottom rot and head rot conditions may develop.
Disease is favored by moist conditions.

Cultural Controls: Use treated seed, rotate
seedbeds and fields, give as good drainage as
possible, and cultivate soon after heavy rains to aerate
and dry soil. Avoid planting in crop debris or in a
recently incorporated green manure crop. See Plant
Pathology Fact Sheet No.1.


Yellows (Fusarium oxysporum f.
conglutinans)

Symptoms: A characteristic yellow-green color
first appears in one or more of the lower leaves and
may progress upward to the top leaves. In some cases,
only one side may be infected and a resultant bending
and curling usually occurs. As the yellow tissue ages,
it turns brown, dies and leaves shed prematurely. A
cross section of the stem shows the vascular tissue
area to be blackened. Vascular tissues in the infected
leaf petioles also show this dark discoloration.

Cultural Controls: The primary control after soil
is infested is use of resistant varieties. Growers
should take every possible precaution to secure
disease-free transplants. Use crop rotation.


Chemical Controls: See PPP-6.




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