Late Blight Control Program Considerations for Tomatoes

Late Blight Control Program Considerations for Tomatoes
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A. A. MacNab, Plant Pathology Dept., Penn State University

A. If no LATE BLIGHT is reported (at least within adjacent states)
B. If LATE BLIGHT is present within 150 miles
C. If LATE BLIGHT is present within a field
D. Fungicides for LATE BLIGHT control on tomatoes
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A. If no LATE BLIGHT is reported (at least within adjacent states):

1. Apply protectant fungicides on the basis of a proven forecast
program (1-800-PENN-IPM), or at regular intervals.
2. When applying fungicide, it is important to obtain complete
coverage of the plant.

B. If LATE BLIGHT is present within 150 miles:

1. Apply a fungicide with some systemic activity (eg. Acrobat,
Tanos, Previcur Flex) + a protectant.
2. For the remainder of the season, apply fungicides at regular
intervals, or adjust timing on the basis of a proven forecasting
program such as BLITECAST.
3. Materials, rates, and intervals may be adjusted based on
weather and the local disease situation.
4. When applying fungicide, it is important to obtain complete
coverage of the plant.

C. If LATE BLIGHT is present within a field:

1. Decide whether to destroy part or all of a planting, or to
continue an aggressive control program for the remainder of the
season. Consider severity, value of the crop, cost to continue an
aggressive control program, increased threat to surrounding fields.
If a good fungicide program was followed before appearance of LATE
BLIGHT, it should be possible to save the crop. If the LATE BLIGHT
fungus has already killed 10% of the foliage, and/or if 5-10% of
green fruit are affected, it could be too late to salvage much of the
crop. IF ONE HAS CROP INSURANCE, THERE SHOULD BE AGREEMENT
WITH AN INSURANCE ADJUSTOR BEFORE A PLANTING IS DESTROYED.
2. If the planting is not destroyed, continue an aggressive
fungicide program to control LATE BLIGHT:
a. Apply sprays for remainder of season.
b. Immediately apply a material with some systemic activity (eg.
Acrobat, Tanos or Curzate) + a protectant.
c. Do not exceed 5-day intervals between sprays as long as there
is active sporulation and spread.
d. During hot dry periods, 7-10 day intervals may be possible.
e. When applying fungicide, it is important to obtain complete
coverage of the plant.

D. Fungicides for LATE BLIGHT control on tomatoes:

1. Some fungicides with some systemic activity for LATE
BLIGHT control:
Acrobat/BASF; 4-day PHI.
Tanos/DuPont; 3-day PHI.
Previcur Flex/Bayer; 5-day PHI.
Whenever any of these fungicides are used for control of LATE BLIGHT,
tank mix with chlorothalonil or mancozeb.
PHI's for some other materials with some systemic activity:
Cabrio = 0-day PHI
Quadris = 1-day PHI
Flint = 3-day PHI
ProPhyt = 0-day PHI

2. Some fungicides with protectant activity for LATE BLIGHT control:
chlorothalonil (Bravo, Echo, Equus): 0-day PHI; in recent tests,
Bravo was a superior protectant fungicide for LATE BLIGHT control.
maneb and mancozeb; 5-day PHI.
Gavel/Dow; 5-day PHI.
Several fixed-copper materials; 0-day PHI.

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