Some Pre-Season Vegetable DIsease Reminders
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A. A. MacNab, Plant Pathology Dept., Penn State University

A.  Celery Leaf Blights  
B.  Cucumber Mosaic 
C.  Muskmelon Powdery Mildew 
D.  Pepper Bacterial Spot 
E.  Pepper Phytophthora Blight  
F.  Sweet Corn Stewart's Bacterial Wilt 
G.  Tomato Bacterial Diseases
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A.  Celery Leaf Blights:  
    -------------------
    Maintain a regular fungicide program in plant beds.  If blights get started 
in plant beds, control will be more difficult and expensive later in production 
fields.
 
B.  Cucumber Mosaic:
    ---------------
    Grow only CMV-resistant varieties.  There is also good resistance to other 
diseases.  Scab and powdery mildew usually are next in importance.  There are 
many good resistant varieties listed in the Vegetable Guide.
 
C.  Muskmelon Powdery Mildew:
    ------------------------
    There are a few varieties with at least partial resistance to powdery mildew.  
These include Earlygold (early only); Athena, Eclipse, and Saticoy (main season); 
and Marygold (casaba type).  Of these, Athena also has the most resistance to 
Fusarium wilt.

D.  Pepper Bacterial Spot:
    ---------------------
    a.  Where bacterial spot has been a problem, consider new varieties which 
have some resistasnce to three races of the bacterial spot pathogen.  These 
varieties include:  Boynton Bell, X3R Aladdin, X3R Camelot, X3R Key West, 
X3R Wizard, Commandant, and Enterprise.
    b.  Use "disease-free" seeds.  If the seed is not determined by the seed 
company to be "free" of the bacterial spot pathogen, consider treating the 
seed as described in the Vegetable Guide.
    c.  Plant peppers only in fields where tomatoes and peppers were not 
grown for at least 2 years.
    d.  Treat seedlings with streptomycin during seedling production; this 
treatment is not possible after transplanting to the field.
    e.  When out-of-state transplants are used, use only PDA-inspected 
plants that are certified by the plant producing state to be produced 
according to practices that minimize chance of disease, and are visibly 
free of disease symptoms.
 
E.  Pepper Phytophthora Blight:  
    --------------------------
    a.  Do everything possible to improve soil drainage, and to prevent water 
runoff through fields.
    b.  Try Paladin and Aristotle, two new varieties with considerable 
resistance.
 
F.  Sweet Corn Stewart's Bacterial Wilt: 
    ----------------------------------- 
    When the winter is mild, flea beetles survive much better than during 
cold winters.  The flea beetles that survive the winter serve as the vectors 
that carry the wilt bacteria to corn plants.  Important controls include use 
of Stewart's Wilt resistant varieties and/or effective control of the flea 
beetle vectors.  Flea beetle controls are listed in the Vegetable Guide.

G.  Tomato Bacterial Diseases:
    -------------------------
    For growers concerned about bacterial diseases on tomatoes, the primary 
controls include starting with pathogen-free seed and disease-free transplants, 
growing the crop in pathogen-free soil (fields), and avoiding working in plantings 
when plant surfaces are wet.  However, an additional control is now available.  
Once plants are established in the field, Actigard can be sprayed on 
plants to help minimize the chance of infection.  Actigard is not a bacticide nor 
a fungicide but is a plant activator that can activate the plant's natural defense 
mechanisms against bacterial and other pathogens.  Although we have limited 
information on degree of effectiveness, growers who have had problems with 
tomato bacterial diseases may be interested in adding this new control 
approach to their current program.

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A. A. MacNab,
Plant Pathology Department, The Pennsylvania State University.
Revised:  May, 2005

Where trade names are used no discrimination is intended, and no endorsement by the Cooperative Extension Service is implied.

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