Early blight
 Bacterial blight

Title: Early, late and bacterial blights of celery
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066867/00001
 Material Information
Title: Early, late and bacterial blights of celery
Series Title: Plant Pathology Fact Sheet PP-8
Physical Description: Book
Language: English
Creator: Kucharek, Tom
Berger, Dick
Affiliation: University of Florida -- Florida Cooperative Extension Service -- Department of Plant Pathology -- Institute of Food and Agricultural Sciences
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: 1979
Spatial Coverage: North America -- United States of America -- Florida
 Record Information
Bibliographic ID: UF00066867
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 by the source institution and holding location.
Resource Identifier: oclc - 51337350

Table of Contents
    Early blight
        Page 1
    Bacterial blight
        Page 2
        Page 3
        Page 4
Full Text

Plant Pathology Fact Sheet

Early, Late, and Bacterial Blights of Celery

Tom Kucharek and Dick Berger, Professor and Extension Plant Pathologist and Professor and Re-
search Plant Pathologist, respectively, Department of Plant Pathology, University of Florida,
Gainesville. 1979; Revised November 2000.

Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean

Three major leaf and petiole blights oc-
cur on celery grown in Florida. Early blight is
the most common and destructive. Bacterial
blight is less common but can be destructive
primarily in the transplant beds. Late blight
occurs in some cool and wet seasons but it is
not an annual problem. Recognizing symptoms
of these diseases and conditions which favor
epidemic development plus knowing what
control measures are available and when they
should be used are all required for efficient and
economical control.

Early Blight

Early blight is caused by the fungus,
Cercospora apii. It occurs on plants in the trans-
plant bed and in the field. On leaf blades, it
produces light brown spots that are somewhat
circular or slightly angular and 1/4 to 3/4 inch
across (Figure 1). Spots may be greasy in ap-
pearance with or without surrounding yellow
halos. A gray fungus growth is often seen on
the spot. On the petiole, elongated, brown to
gray lesions are formed.

An epidemic begins when microscopic
spores (produced on seed, old infected celery
debris on the soil, spots on volunteer celery
plants or spots on nearby celery plantings) are
blown by wind to susceptible celery leaves or
petioles. Spores are produced predominately
at night when temperatures range from 58 F to
86F for at least 10 hours, if the relative humid-

ity is near 100 percent during the same period
of time. Most spores are released for wind dis-
persal when the relative humidity decreases
during mid to late morning hours. Movement
of equipment (tractors, harvesters) in the field
also cause release of high numbers of spores
which can be blown to nearby celery fields. Af-
ter landing upon susceptible host tissue and
when moisture is present; spores germinate,
penetrate the tissue, spread within, and pro-
duce symptoms in 12-14 days. More spores are
then produced on the new spots and the epi-
demic is in full swing.

Control of early blight is achieved effi-
ciently and economically when several tech-
niques are used collectively. 1) Disease-free
transplants should be produced by using a rig-
orous spray program as diseased transplants
have an overriding influence over other subse-
quent control measures. 2) Use resistant variet-
ies. Such varieties will reduce, but not elimi-
nate, early blight. 3) Spray with a fungicide rec-
ommended by your county Extension agent
immediately after transplanting. 4) Celery trans-
plants in late summer to early fall may need
sprays two to four times weekly in South
Florida, as blight favorable weather (BFW) oc-
curs commonly during this time. By late fall and
during winter months BFW occurs on a spo-
radic basis thus allowing you to use available
forecasting systems. During spring months
BFW will become more common, thus dictat-
ing frequent sprays again. Use fungicides rec-


ommended by your county Extension agent. 5)
Celery plantings that are downwind, and within
one-half mile of a field being harvested, should
be sprayed just prior to the harvesting opera-
Bacterial Blight

Bacterial blight is caused by the bacte-
rium Pseudomonas cichorii. Bacterial blight may
appear similar to early blight except that bacte-
rial blight spots are smaller, more angular, and
reddish in color. Bacterial blight has a more
sharply delineated border compared to early
blight (Figure 2). From a few lesions on infected
seedlings, rain, irrigation, or movement of ma-
chines and people can spread bacteria to other
plants. Bacterial cells enter plant tissue through
natural openings stomatess, hydathodes) or
wounds. Within a few days from entrance,
symptoms appear. Bacterial blight is favored
by warm, wet weather. Another manifestation
of P. ccihorii in celery is the presence of long,
brown, firm discolorations in the petioles. This
disorder is called brown stem and is a problem
in the field during wet seasons. See Fact Sheet
PP-126 (by Pernezny et. al.) for information on
symptoms and control of Brown Stem.

Bacterial blight is controlled by using
several techniques. 1) Minimize working in
transplant beds when plants are wet. 2) If top-
ping is needed to harden transplants, top mow
transplants when they are dry and apply an ap-
proved copper fungicide immediately after top-
ping. 3) Include an approved copper fungicide

in your spraying of transplants, especially if
bacterial blight is present. 4) Use subsurface ir-
rigation rather than overhead irrigation in trans-
plant beds.
Late Blight

Late blight is caused by the fungus
Septoria apiicola. It is similar in appearance to
early blight in spot size and shape (Figure 3).
However, late blight often will have black
pimple-like spore-bearing structures (pycnidia)
within the spot. With the aid of a hand lens,
tendrils of spores can be seen oozing from pyc-
nidia when leaves are wet. Thus, late blight
spores are dispersed primarily by rain, equip-
ment and people. Infected seed is the primary
source of inoculum (pycnidia with spores) (Fig-
ure 4). After spores are deposited on suscep-
tible host tissue by rain or mechanical means,
they germinate, penetrate, and grow within the
tissue for 9-12 days after which symptoms are
produced. Late blight is favored by rain plus
cool temperatures (50-81F).

Control is achieved by: 1) Using disease-
free seed. Two year old seed is usually free of
viable inoculum. 2) Staying out of transplant
beds when plants are wet. 3) Using fungicides
recommended by your county Extension agent.


Figure 1. Early blight lesions in celery leaf.

Figure 2. Bacterial blight in celery leaf.

Figure 3. Late blight lesions in celery leaf.


i: T.'' r LI V

Figure 4. Celery seed without and with Septoria.

1 *,

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