Georgia Extension Vegetable News
The University of Georgia
Cooperative Extension Service
College of Agriculture and Environmental Sciences / P.O. Box 1209, Tifton, GA 31793
The Cooperative Extension Service, and the University of Georgia College of Agricultural and Environmental Sciences does not
guarantee or warrant any product mentioned; neither does the use of a trade or brand imply approval of any product to the exclusion
of others which may also be suitable. Trade names are for information only. The University of Georgia, the Cooperative Extension
Service, and the University of Georgia College of Agricultural and Environmental Sciences offers educational programs, assistance
and materials to all people without regard to race, color, national origin, age, sex or disability and are equal opportunity/affirmative
action organizations committed to a diverse work force.
Volume 3, No.1
Contents...
Sclerotinia Problems
Greenhouse Disease Issues
Sandea Label
European Corn Borer Program Deadline
Plant Disease Clinic
March 2003
also be used on carrots, although the carrot label only
lists control of Alternaria leaf spot. Topsin M may
also be used on beans.
Sclerotinia Problems
David Langston
Extension Vegetable Pathologist - UGA
Cool, wet weather during this time of year can
promote problems with diseases caused by
Sclerotinia sclerotiorum. This is one of the most
damaging fungal diseases of brassicas and carrots
during the winter months and is strictly a coolweather disease. This disease is causes a rapid
breakdown of plant tissue due to an acid that the
fungus produces as it attacks plants. Cottony, white
mycelium can also be seen near the infection front
of the lesion. Once tissue has been destroyed, large,
black, irregularly shaped sclerotia are formed and
serve as survival structures that can infect
subsequent crops for several years. Damage on
carrot appears usually at the soil line and causes the
foliage to rapidly collapse (Fig 1. The fungus
causes large areas of tissue collapse on brassicas
(Fig 2) and the sclerotia can be readily seen on
cabbage heads (Fig 3), hence the name "raisin
head".
Control of this disease is usually best using rotation
and deep turning. However, some fungicides are
labeled for preventive suppression of this fungus.
Rovral is labeled on beans for Sclerotinia but can
Figure 1. Sclerotinia damage on carrots.
Figure 2. Large, water-soaked lesions on brassicas.
Page 1
Sandea Label
Stanley Culpepper
Extension Weed Scientist - UGA
Figure 3. Sclerotia of Sclerotinia causing raisin
head.
Greenhouse Disease Issues
David Langston
Extension Vegetable Pathologist - UGA
Once gain, we are seeing a lot of diseases in
greenhouse-grown transplants this spring. The
main problems we see are caused by Pythium spp.
, Rhizoctonia solani, Pseudomonas syringae pv.
syringae, or Acidivorax avenae subsp. citrulli (fruit
blotch). What generally happens is transplant
growers will try to hold back plants because they
will be ready to transplant before growers can use
them (usually because of wet field conditions).
When we have wet field conditions, greenhouse
conditions also favor disease because of high
relaive humidity and overcast skies that don't allow
proper drying of foliage and plant media. Another
issue is the lack of effective, legal, pesticides for
use in the greenhouse. Generally, if a pesticide is
labeled in the field for a certain crop it can be used
in the greenhouse unless the label specifically
prohibits the use. What is recommended is for
growers to use fans to promote air circulation and
reduce humidity. Also, use fungicides that are
labeled for greenhouse use. Thirdly, if bacteria are
present, send a sample to the Tifton plant disease
clinic to determine if the disease will result in field
losses) such as fruit blotch.
Sandea Labeled for Watermelon, Squash, and
Pumpkin Row Middles ONLY.
For the 2003 production season, Sandea use in the
aforementioned crops will be limited to row middle
applications only. Apply 0.5 to 1.0 oz of Sandea per
broadcast acre between rows of direct seeded or
transplanted plants for the control of nutsedge,
pigweeds and other sensitive weed species.
DO NOT allow Sandea to contact the crop as injury
will likely occur. If plastic is used adjust equipment
to not spray the plastic or contact the crop. Multiple
applications can be made but one should not exceed
a total use of 2 oz/A per 12-month period. Carryover
of Sandea is a threat for many vegetable crops;
therefore, read the Sandea label carefully prior to
using the product.
DO NOT spray Sandea overtop of plastic and then
transplant one of these crops into that plastic.
Page 2
European Corn Borer Program
Spring Deadline
Stormy Sparks
Extension Vegetable Entomologist
Georgia producers planning to ship sweet corn or
green beans to California or Texas, or pepper to
Texas, need to be signed up for the European
Corn Borer Program by March 15 (for the spring
crop). If they are planning to ship to California,
the program requires trapping for European Corn
Borer adults in each field, in addition to regular
insecticide applications. The traps and
pheromones are furnished by the grower, and all
traps are monitored weekly by the Georgia
Department of Agriculture. Capture of two adults
in a field in a single week eliminates that field
from the program. The Texas program does not
require trapping, but does require regular
insecticide treatments. Availability of insecticide
application records is required for both programs.
The final hurdle in both programs is inspection of
shipments. Detection of a single European Corn
Borer larvae in a shipment eliminates that
shipment and future shipments from the
individual field for the rest of the season.
The cost of the program varies with the targeted
shipment State. The California program requires
trapping. The growers must supply the traps and
pheromones and pay an inspection fee of $3 per
acre (this basically covers the cost of checking the
traps). The Texas program requires a State
Phytosanitary Certificate with each shipment,
which costs $35 per certificate.
The deadline for application for these programs
for the spring crop is March 15. For the fall crop,
the deadline is August 1. Growers interested in
participating in this program should contact Barry
Smith with the Georgia Department of
Agriculture at 229-383-3464.
On a final note, I encourage close cooperation and
compliance with these programs and similar
programs. While compliance does have some cost
to the grower, any detected non-compliance by
the cooperating State could result in cancellation of
the program and hurt the entire industry.
Tifton Plant Disease Clinic
Jason Brock
Plant Disease Diagnostician -UGA
Looking Ahead
March marks the beginning of the busiest time of
year for the Tifton Plant Disease Clinic. When
looking for clues on what types of problems to
expect, the first place to look should be the past.
After reviewing the clinic records for the past three
years, I can group anticipated samples into three
main categories: 1) common leaf spots, 2) fruit
blotch “scares”, and 3) soil-born diseases.
1) Alternaria leaf spot, Cercospora leaf spot,
downy mildew, gummy stem blight, and powdery
mildew have been diagnosed on past samples
during March and April. Each of these pathogens
have characteristics that make the diagnosis fairly
straight-forward. An excellent resource for
assistance in diagnosing these diseases is the
CAES bulletin “Fungal Identification From Plant
Material”
(http://www.plant.uga.edu/Extension/pubs/Fungali
dbook.html).
2) Fruit blotch is a major concern with cucurbit
crops. Other bacteria and chemical injuries often
mimic the symptoms of fruit blotch. An accurate
diagnosis depends on isolation and laboratory
testing of the pathogen. Each year, the clinic
receives samples related to fruit blotch-type
symptoms.
3) During March and April, the majority of plant
disease samples have been due to soil-borne
pathogens. Pythium sp., Phytophthora sp.,
Rhizoctonia solani, Sclerotium rolfsii, and
Sclerotinia sp. all belong to this group. Information
about these pathogens is also included in the
CAES publication mentioned above.
Page 3
Sclerotium rolfsii and Sclerotinia sp. both produce
sclerotia that are useful diagnostic structures.
Hyphae of Rhizoctonia solani and
Pythium/Phytophthora species can be used to
make a diagnosis. Rhizoctonia hyphae contain
cross walls, branch at 90 degree angles with
constrictions at the base, and have a light brown
appearance. Pythium and Phytophthora hyphae
lack cross walls. Many times, the pathogen has to
be isolated or grown out of the plant tissue.
Another CAES publication that might be useful is
“A Simplified Technique for Recovering Pythium
and Phytophthora from Infected Plant Tissue”
(http://www.ces.uga.edu/pubcd/MP-104.htm)
Looking Back
Botrytis allii
Pantoea ananatis
Xanthomonas sp. (2)
disease symptoms (2)
chemical injury
Pepper:
Anthracnose
unknown (2)
Pumpkin:
disease symptoms
Pea:
Powdery mildew
Squash:
Downy mildew
Potyvirus
Tomato:
Target spot (Corynespora
cassiicola)
Tomato Spotted Wilt (2)
Tobacco Mosaic (4)
Tomato Yellow Leaf Curl
Turnip:
Cercospora leaf spot (4)
Rhizoctonia solani
Xanthomonas campestris (2)
Pseudomonas sp.
no disease
The following is a summary of the commercial
vegetable samples diagnosed since the September,
2002 newsletter. Note: The number indicates the
number of samples diagnosed.
Bean:
no disease
Broccoli:
Sclerotinia rot
unknown
Cabbage:
Collard:
Cucumber:
Onion:
Alternaria leaf spot
Rhizoctonia solani
Xanthomonas campestris (6)
Pseudomonas syringae (4)
disease symptoms
Cercospora leaf spot
Xanthomonas sp. (3)
Cabbage leaf curl
Probable sting nematode
chemical injury
unknown
Pythium root rot
no disease
unknown
poor pollination
physical injury
Watermelon: Target cluster (unexplained
disorder)
no disease (2)
Georgia Extension Vegetable News
Volume 3, No.1.
Spring 2003
Editor . . . . . . . . . . . . . . . David B. Langston, Jr.
Production Assistant & Webmaster . Paul Sumner
This newsletter is also available on the World
Wide Web at www.cpes.peachnet.edu/veg.
County Extension Agent
Fusarium foot rot
Page 4