June Disease Reminders

June Disease Reminders for Commercial Producers in PA
====================================================
A. A. MacNab, Plant Pathology Dept., Penn State University
A. Beans
B. Celery
C. Cucumber
D. Muskmelon
E. Peppers
F. Sweet Corn
G. Tomato
====================================================
The following diseases should be considered early in June. Some will appear in June.
For others, control measures must be taken now to minimize disease severity later in
the season. Growers who have experienced significant losses from diseases should
review diagnosis and control information. Diagnosis informatio is available in the PSU
publication titled "Identifying Diseases of Vegetables". Control information is
available in "Commercial Vegetable Production Recommendations".

A. Beans:
Mosaic viruses: For commercial plantings, do not make successive plantings in
adjacent areas; although few plants may be affected in early plantings, number of
plants affected usually increases in successive plantings as more virus inoculum from
previous plantings becomes available to aphid vectors. Do not plant near clovers; they
are a source of viruses that can affect beans. Maximum density plantings may
minimize losses.

B. Celery:
Leaf blight: 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.

C. Cucumber:
1. Bacterial wilt: Stop the vector (cucumber beetle) from feeding on plants.
Several insecticides provide good control. Maximum density plantings may minimize
losses.
2. Mosaic: Grow only CMV-resistant vars. There is also good resistance to other
diseases. Scab and powdery mildew usually are next in importance.

D. Muskmelon:
1. Collapse: This late-season problem can be avoided by promoting early harvest.
Polyethylene mulch is important in many areas of Pennsylvania.
2. Powdery mildew: When possible, gardeners should use powdery mildew resistant
varieties such as Earlygold (early only); Saticoy, Eclipse, and Athena (roadside and
shipping type); and Marygold (casaba type). When necessary, fungicides can be used
later in the season. Two new strobilurin fungicides, Quadris and Flint, are labelled for
use, with either one alternated with Bravo.
3. Fusarium wilt: If long rotation is not possible, use resistant varieties such as
Athena (res to races 0, 1 and 2), Saticoy (res to race 2), Superstar (res to race 2), and
Eclipse (res to race 2).

E. Peppers:
1. Bacterial leaf spot: Start with disease-free plants. Where diseases are
expected, follow a regular preventive spray program. Start early and continue with
fixed copper for several weeks until you are relatively certain young plants are not
carrying the bacterial pathogen. The following new varieties have resistance to races
1, 2, and 3 of the pathogen: Boynton Bell, Commandant, Enterprise, X3R Camelot, and
X3R Wizzard.
2. Viruses: Where viruses have been a problem, plant only varieties resistant to
TMV and, when possible, to other viruses. Maximum density plantings may minimize
losses. Aphid controls followed to stop transmission of aphid-borne viruses (CMV and
Etch) have not been very successful for virus control.

F. Sweet Corn:
1. Stewart's bacterial wilt: Control of the flea beetle vector is the key to control
for susceptible varieties.
2. MDM Virus: Where this virus was a problem in past years, try varieties claimed
to be resistant. A couple are listed in the Commercial Vegetable Guide (Earlibelle,
Merit). Maximum density planting may minimize losses. This disease usually is not
important in early plantings.

G. Tomato:
1. Bact. spot and speck: Where inoculum is suspected (old tomato fields,
transplants with symptoms), spray with a tank mixture of fixed copper plus either
maneb or mancozeb, or with ManKocide. Start as soon as plants are established and
continue at 7 to 10 day intervals, especially during wet periods.
2. Early blight: In new fields where disease-free transplants were used, fungicide
sprays should not be needed until the end of June. However, if diseased transplants
were planted, or if fields were planted to tomatoes last year, start a preventive spray
program early. Quadris, Flint and Cabrio are new fungicides that are excellent for
control of tomato early blight.
3. Late blight: Primary inoculum can be introduced with infected seed tubers, from
cull piles, and in/on volunteer potato plants. Inoculum also could be introduced with
tomato transplants. If inoculum is present, late blight will have the potential to
develop whenever environment favors the disease (wet and cool conditions). The major
control after plantings are established is to keep plants covered with protective
fungicides whenever environment favors the disease.
-------------------------------------------------------------
A. A. MacNab,
Plant Pathology Department, The Pennsylvania State University.
Reviewed: June, 2005
Information provided is intended for consideration by the user, but is not intended to be a recommendation. Production decisions should be based on consideration of many types of information (scientific, experiential, economic, legal, etc.) available to the user.
Where trade names are used no discrimination is intended, and no endorsement by the Cooperative Extension Service is implied.
Back