July Disease Reminders for Commercial Producers in PA
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A. A. MacNab, Plant Pathology Dept., Penn State University

A.  ASPARAGUS
B.  BEANS
C.  BEANS, LIMAS
D.  BEETS
E.  CABBAGE:
F.  CARROTS and CELERY
G.  CUCURBITS
H.  EGGPLANT
I.  ONIONS
J.  PEPPER
K.  PUMPKIN and SQUASH
L.  SWEET CORN
M.  TOMATOES
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    Some vegetable diseases will begin to appear in July.  Others will get 
started then although symptoms may not appear until August.  In addition 
to the following notes, controls are presented in the "Commercial Vegetable 
Production Guide".  Identification information is available in the colored 
publication, "Identifying Vegetable Diseases" which is available from the 
Penn State Campus at University Park, PA and from most Pennsylvania 
Extension Offices.

A.  ASPARAGUS
    Rust:  Apply fungicide to young plantings, whether "resistant" or 
susceptible.  During the years before harvest is started, and when fern 
growth becomes heavy relatively early, fungicides can be especially 
important because of the dense growth.

B.  BEANS
    Mosaic Viruses:  Use resistance to BV-1.  Provide good weed control; 
weeds are a source of bean viruses.  Do not plant near clovers; they are 
a source of bean viruses.  Do not make successive plantings in adjacent 
strips or fields; the few diseased plants that appear in early plantings 
act as an important virus source for later adjacent plantings.

    White Mold and Gray Mold:  Wet weather will promote this disease.  
Apply protective fungicide sprays where needed.  Wet conditions 
immediately before and during bloom promote disease development. 
Ronilan provides excellent control for snap beans.  Additional fungicides 
listed in the Vegetable Guide are Endura, Topsin M and Rovral.

C.  BEANS, LIMAS
    Downy Mildew:  During wet weather, when conditions favor disease, 
use fungicides.  See the Vegetable Guide for details.

D.  BEETS
    Leaf Spots:  Use fungicides where disease usually occurs.

E.  CABBAGE:
    Fusarium Yellows:  This disease is favored by hot weather.  When 
possible, avoid susceptible varieties.

    Clubroot:  Wet conditions sometimes promote development.  Where 
present, it is too late to apply controls for this year.  Determine the 
source if possible.  Then plan rotation, pH adjustment, or Terraclor 
use (WP only) for next season.

    Downy Mildew and Leaf Spots:  These diseases become most important 
late in the season.  Where anticipated and warranted, fungicides provide 
some control.  For downy mildew, Ridomil Gold/Bravo 81W (1.5 to 2 lb/A) 
can be applied at 14-day intervals until 7 days before harvest.  Other 
fungicides for both diseases include Bravo and maneb.  Aliette is very 
good for downy mildew but does not control Alternaria leaf spot.  Also, 
Amistar/Quadris is good for Alternaria leaf spot but is not labelled for 
downy mildew.

F.  CARROTS and CELERY
    Leaf Spots:  Continue fungicide sprays; they are most important for 
the remainder of the season.

G.  CUCURBITS
    Bacterial Wilt:  Where present, it may be too late to obtain control 
this year.  For plants that are free of disease, continue control of the 
cucumber beetles (bacteria carrier) as long as necessary.

    Leaf Spots, Blights, and Powdery Mildew:  Use regular fungicide 
sprays unless varieties are resistant to the diseases of concern.  Leaf 
diseases are of major importance on muskmelons (cantaloupes) during 
late season. Fungicides are outlined in the Vegetable Production Guide.  
Follow the resistance management program closely to minimize the
risk of the powdery mildew fungus developing resistance to fungicides.

    Downy Mildew:  This disease occured early and was more important
than usual in 2004.  In 2005, downy mildew appeared 2-weeks earlier 
than usual in southern New Jersey by mid-June.  Consequently, this
disease could be even more important in Pennsylvania in 2005 than it 
was in 2004.  I am recommending that protective sprays be applied 
about 2 weeks earlier than downy mildew appeared in local plantings
in 2004.  The fungicides are listen in the 2005 Commercial Vegetable 
Production Guide.

    Scab:  For susceptible varieties, use fungicides when conditions are 
cool and wet.  For cucumbers, use resistant varieties for next year.

    Mosaic Viruses:  Use resistant varieties.  When resistant varieties 
are not available, control perennial weeds, plant in large fields, and 
control aphids.

    Fusarium Wilt:  It is too late to apply controls for this year.  For 
future years, try rotation, resistance when available (eg. Athena has 
resistance to Races 1 and 2), and if necessary, soil fumigation.

H.  EGGPLANT
    Verticillium Wilt:  Follow rotations that avoid susceptible crops for 
as many years as possible.  Where present yearly, consider fumigation
 where crop value warrants the expense.

I.  ONIONS
    Leaf Spots:  Apply fungicides on a regular schedule, especially for 
those planned for storage.

J.  PEPPER
    Mosaics and Virus Spots:  It is too late to affect control for this year. 
 For future years, use TMV resistance, plant in large fields, control aphid 
vectors, and eliminate perennial weeds near fields.

    Bacterial Spot:  When possible, grow varieties with resistance to 
bacterial spot.  Some varieties are resistant to more than one race.

Resistant to Races 1, 2, and 3:
  Boynton Bell, Aristotle, Commandant, Enterprise, X3R Camelot, 
X3R Wizard, and X3R Key West.
Resistant to Races 1 and 2:
  Admiral
Resistant to Race 2:
  King Arthur
Resistant to unspecified race:
  Renegade.

Where present, determine bacterial spot source.  Did it come on plants?  
If present, Spray weekly with a tank mixture of basic copper plus maneb. 
 Plan to rotate to fields not recently planted to tomatoes or peppers.

K.  PUMPKIN and SQUASH
    Powdery mildew:  Powdery mildew has been important in recent years. 
Some new varieties are being developed with various levels of resistance. 
When powdery mildew is present, fungicides are suggested for summer 
squash, and for winter squash and Halloween pumpkins.  Fungicides are 
outlined in the Vegetable Production Guide.  Follow the resistance 
management program closely to minimize the risk of the powdery mildew 
fungus developing resistance to fungicides.

    Downy Mildew:  This disease occured early and was more important
than usual in 2004.  In 2005, downy mildew appeared 2-weeks earlier 
than usual in southern New Jersey by mid-June.  Consequently, this
disease could be even more important in Pennsylvania in 2005 than it 
was in 2004.  I am recommending that protective sprays be applied 
about 2 weeks earlier than downy mildew appeared in local plantings
in 2004.  The fungicides are listen in the 2005 Commercial Vegetable 
Production Guide.

L.  SWEET CORN
    Leaf Spots and Rust:  Quadris is now labelled and provides superior 
control.  Tilt also is very effective.  Bravo, maneb, and mancozeb are 
helpful.

    Maize Dwarf Mosaic (MDM):  Aphid vector control may help in large 
fields.  Where MDM is prersent, plan to try tolerant varieties in future 
years.

M.  TOMATOES
    Bacterial Speck and Spot:  If spots are a yearly problem, and 
symptoms appear on leaves, continue sprays with basic copper plus 
maneb/mancozeb. Next year, rotate to new fields, use pathogen-free 
seed, and spray seedlings regularly with streptomycin before 
transplanting.

    Early blight:  If early blight is bad, rotate and insure adequate 
fertility for next years crop; in most cases, fungicides should begin 
not later than first appearance of early blight symptoms.  Quadris, 
Flint, and Cabrio are exciting new fungicides now labelled for use 
on tomatoes; rates are listed in the Commercial Vegetable Guide.  
These fungicides provide outstanding control of early blight and 
Septoria leaf spot.  Where used, these fungicides should be alternated 
with fungicides having modes of action that are different from 
those of other materials in the fungicide program.

    Late Blight:  Although 2005 early season weather conditions have 
not favorable late blight development, I am concerned that late blight
could become a problem in 2005, especially since it has already been
verified to be present in a commercial potato field in southern New 
Jersey.  Check the 1-800-PENN-IPM toll free phone line for updates 
regarding the late blight disease situation.  Fungicides for late 
blight are listed in the Commercial Vegetable Guide.  For tomatoes, 
Bravo was especially effective in our 1997, 1998, and 1999 tomato 
trials.  And the following fungicides have translaminar systemic 
activity for control of late blight:  Tanos, Acrobat, and Previcur Flex.

Alan MacNab, Plant Pathology Dept., Penn State Univ.
Revised:  July 1, 2005.