Title: Florida plant disease management guide
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Permanent Link: http://ufdc.ufl.edu/UF00053871/00010
 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: VID00010
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 44549741
lccn - 00229071
 Related Items
Preceded by: Florida plant disease control guide

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PDMG-V3-38
UF UNIVERSITY of

UFFLORIDA
IFAS Extension



2007 Florida Plant Disease Management Guide:

Cucumber1


Pamela Roberts and Tom Kucharek 2


Specific Common Diseases

Angular Leaf Spot (Pseudomonas syringae
pv. lachrymans)

Symptoms: Infections are found on the leaves,
stems, and fruit. Spots on the leaves are typically
angular and water-soaked. Free moisture allows the
bacteria to ooze from the spots which, upon drying,
leaves a white residue. These spots of dead tissue will
occasionally drop away from the healthy tissue
leaving irregular holes in the leaves.

The spots on the fruit are generally smaller,
nearly circular and slightly depressed. Early external
fruit infections may be so small as to be impossible to
cull out during packing. Internal symptoms, however,
are quite obvious. The internal flesh discolors
(brown) from below the skin lesion down to the seed
layer within the fruit and may run the entire length of
the fruit. Older fruit lesions turn white with an
obvious tissue cracking. This disease is apt to be
severe during wet springs and is rain-splash
dispersed. The causal bacterium can infect


watermelons as well and can survive in infected crop
debris. The bacterium is seedbome.

Cultural Controls: Use disease-free seed and
rotate crops to avoid this pathogen surviving in crop
debris. Avoid working or harvesting fields while
foliage is wet. Mechanical spread of the bacterial
pathogen is likely. Rotate crops with non-hosts.

Chemical Controls: See PPP-6.

Anthracnose (Colletotrichum
lagenariumlGlomerella cingulata)

Symptoms: The disease first appears on the
foliage as small, yellow or reddish-brown,
water-soaked spots often on veins, which enlarge
rapidly and turn brown. The dead tissue dries and may
crack and fall out. On the stems, the lesions are
elongated and light brown to black in color. In fruit,
circular, water-soaked, sunken lesions appear,
varying in size with the age. Lesions turn dark green
to brown. During wet weather, the centers of the
spots often show a pinkish color due to production of
spores of the causal fungus.


1. This document is PDMG-V3-38, one of a series of the Department of Plant Pathology, 2007 Florida Plant Disease Management Guide, Florida
Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Reviewed January 2007. Please visit the EDIS Web site
at http://edis.ifas.ufl.edu.
2. Pamela D. Roberts, associate professor, Plant Pathology Department, Southwest Florida Research and Education Center, Immokalee, FL; T.A. Kucharek,
professor emeritus, Plant Pathology Department, Florida Cooperative Extension Service, Insitute of Food and Agricultural Sciences, University of Florida,
Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products
named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.

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






2007 Florida Plant Disease Management Guide: Cucumber 2


This disease is particularly severe during wet
seasons where temperatures remain between 70 and
80 F. The causal fungus can survive in old crop debris
and on weed hosts. This fungus is known to infect
balsam pear (Momordica sp.), bottle-gourd
(Lagenaria sp.), cantaloupe, chayote (Sechium sp.),
mock cucumber (Echinocystis sp.), and watermelon.

Cultural Controls: Choose resistant varieties.
Avoid working fields when plant foliage is wet. Deep
plow plant residue and practice crop rotation. Use
disease-free seed.

Chemical Controls: See PPP-6.

Belly Rot (Rhizoctonia solani)

Symptoms: This disease is caused by a common
soilbome fungus which infects the ground (belly)
side of fruit. Young cucumbers exhibit a yellow
reddish-brown, superficial discoloration which
develops into a sunken, irregular lesion or pit in the
fruit underside. Mature fruits develop a large,
water-soaked decay. This disease proceeds rapidly
above 820 F and in periods of high humidity, a
dense, light brown mold growth develops from the
lesions on the fruit.

Cultural Controls: Incorporate the previous crop
or weed debris at least 4-6 weeks prior to planting.
The use of full bed plastic mulch will greatly reduce
disease incidence where fruit is produced on the
plastic. See Plant Pathology Fact Sheet PP-41.

Chemical Controls: See PPP-6.

Cottony Leak (Pythium spp.)

Symptoms: This disease is primarily a fruit rot
but the causal fungus can cause a damping-off of
seedlings or produce vine cankers during unusually
wet growing seasons. In the field, the fungus can
enter the fruit through old floral parts or directly from
the soil. The fungus produces dark green,
water-soaked lesions. The fruit become soft and
mushy very rapidly and may be completely covered
with white, cottony mycelium during warm, wet
weather. Fruit rot can occur rapidly in transit when
conditions are moist since the fungus spreads by
fruit-to-fruit contact.


Cultural Controls: Plant only in well-drained
fields. Avoid picking fruits from infested areas of the
field. Infected fruits will contaminate adjacent fruits
in buckets or hampers or other picking containers.

Chemical Controls: See PPP-6.

Damping-off (Pythium spp., Fusarium sp.,
Rhizoctonia solani)

Symptoms: Seed fails to germinate due to rapid
colonization of seed by soilbome fungi. Excavated
seed will be rotted and soft, often with evidence of
fungal mycelium. Young, newly emerged seedlings
often collapse at soil line and topple over. The stems
may exhibit an obvious discoloration ranging in color
from a reddish-brown to black and may be dry or
mushy to the touch depending on the soil fungus
involved.

Cultural Controls: Avoid planting seed when
soil moisture, soil preparation, temperature or
planting depth do not favor rapid emergence. Plant in
well tilled soil where old crop and weed residue has
been plowed down 30 days previously. Plant
fungicide-treated seeds. See Plant Pathology Fact
Sheet No. 1.

Chemical Controls: See PPP-6.

Downy Mildew (Pseudoperonospora
cubensis)

Symptoms: The disease first shows as angular,
yellow spots on the upper leaf surface. If the weather
is humid and warm, a gray mold growth is evident on
the under surface. As the spots enlarge, a general leaf
yellowing develops followed by browning and death
of leaf tissue. Usually the first symptoms are on older
leaves and they gradually move outward. Periods of
wet weather, heavy dews or fog are favorable for
severe disease occurrence. Spores are dispersed by
the wind. See Plant Pathology Fact Sheet PP-2.

Cultural Controls: Choose downy
mildew-resistant varieties, although recent outbreaks
may indicate that resistance alone will not control this
disease. Avoid working fields when plant foliage is
wet. Maintain a preventative fungicide control
program during wet, humid weather.






2007 Florida Plant Disease Management Guide: Cucumber 3


Chemical Controls: See PPP-6.

Fusarium Wilt (Fusarium oxysporum f. sp.
cucumerinum)

Symptoms: This is not a common disease in
Florida. The causal fungus is soilbome and may
infect the cucumber at any stage of growth. Freshly
seeded cucumbers may damp-off below ground or as
newly emerged seedlings. If older plants are infected
prior to vine elongation, the entire plant will exhibit a
mid-day wilt. After several days of wilting, leaves
will tip bum followed closely by a complete wilt and
plant death. Plants infected in the vining stage of
growth will often wilt in only one or two runners.

Diagnostic field symptoms are the wilting
syndrome and the brown discoloration of the vascular
tissue within the lower stem when split open. In moist
weather, the whitish-pink fungal mycelium may be
observed on the outside of the lower stems. See Plant
Pathology Circular 1025.

Cultural Controls: Rotate with other crops such
as crucifers, legumes or solanaceous plants.
Occurrence of this disease in commercial
greenhouses should be controlled through sanitation
of infected plants and soil fumigation. Raising the
soil pH reduces this disease.

Gummy Stem Blight (Didymella
bryoniae/Phoma cucurbitacearum)

Symptoms: This has not been a common problem
on cucumbers in Florida. Lesions in the cotyledons
and leaves are round or irregular, brown and with a
faint zonation. Lesions in the crown and stems are
brown, usually turn white with age and often exhibit
a sap flow. The disease will usually begin at the
crown and progress outward on the vines.

The causal fungus is seedbome and can survive
on crop and weed host debris. Secondary spread is by
rain-splashed spores. The fungal pathogen is known
to infect cantaloupe, chayote, pumpkin, squash and
watermelon. The black, speck-like fruiting structures
(pycnidia) can often be found in lesions. See Plant
Pathology Fact Sheet PP-27.

Cultural Controls: Use resistant varieties. Use
fungicide-treated seed and initiate a fungicide spray


program at first disease appearance. Avoid planting in
fields with residual crop debris. Use healthy
transplants.

Chemical Controls: See PPP-6.

Powdery Mildew (Erysiphe
spp.lSphaerotheca fulginea)

Symptoms: These fungi infect leaves and stems.
Round whitish spots on the underside of the older
leaves appear. The spots increase in size, coalesce,
appear on the upper surface with a white powdery
growth. Severely affected leaves lose their normal
dark-green color and become pale yellow-green, then
brown and shriveled. The young stems may also be
killed. Fruits may sunscald as a result of loss of
foliage. Spores are readily wind-dispersed over long
distances.

Cultural Controls: Plant resistant varieties.
Excellent resistance is available.

Chemical Controls: See PPP-6.

Scab (Cladosporium cucumerinum)

Symptoms: On the leaves, the fungus produces
small brown spots with yellow margins. The brown
center may fall out leaving a ragged hole. Young
leaves at the vine tips may become distorted. The
greatest damage is to the fruit. Here small sunken
dark gray spots appear, and a sticky material oozes
from the spots. As the spots enlarge, they often run
together forming large scab-like diseased areas. In
humid periods, spores are produced giving the spots
an olive-green color.

This disease is most severe in cool weather. The
causal fungus can be seedbome or survive on old
cucumber crop debris. Spores can be carried by air
currents or spread by water splashing, clothing, or
tools.

Cultural Controls: Exercise crop rotation for at
least three years where this disease is a problem. Plant
resistant varieties and achieve additional control
through the use of fungicides.

Chemical Controls: See PPP-6.






2007 Florida Plant Disease Management Guide: Cucumber 4


Target Spot (Corynespora cassiicola)

Symptoms: Symptoms often look the same as
downy mildew. Target spot begins on leaves as
yellow to white leaf flecks, becoming angular with a
definite outline. Later, the spots become circular with
light brown centers surrounded by dark-brown
margins.

Individual lesions are 1/8 to 3/8 inch in diameter.
Lesions coalesce and produce larger dead areas with
drying and shredding of leaves. Fungus survives on
infested plant material and conidia are readily
airborne dispersed

Cultural Controls: Avoid working infested fields
when they are wet. Remove and destroy infected
plant debris. Apply fungicides as needed to control
this disease.

Chemical Controls: See PPP-6.

Viruses (Papaya Ringspot Virus Type W,
Cucumber mosaic virus, Zucchini yellow
mosaic virus, Watermelon mosaic virus 2)

Symptoms: Leaves show varying degrees of
mosaic, distortion, and stunting. Fruits may also be
mottled and deformed. These viruses are
aphid-transmitted and can infect cantaloupe, squash,
watermelon and a number of common weeds
including balsam pear (Momordica sp.), bur
cucumber (Sicyos sp.), citron (Citrullus vulgaris var.
citroides), creeping cucumber (Melothria sp.)
plantain (Plantago major), Sesbania sp., showy
crotalaria (Crotalaria spectabilis), sweet clover
(Meliotus indicus), alyceclover (Alysicarpus sp.) and
many other plant species. See Plant Pathology
Circular 1184.

Cultural Controls: Maintain weed control in and
around cucumber plantings. Insecticide control of the
aphid vector is not recommended because of the
rapid transmission of the virus during aphid feeding.

Chemical Controls: See PPP-6 for use of JMS
Stylet Oil.




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