PENNSYLVANIA VEGETABLE DISEASE UPDATE
JULY 2, 2013
Beth K. Gugino
Assistant Professor Vegetable Pathology
Department of Plant Pathology
and Environmental Microbiology
219 Buckhout Lab
University Park, PA 16802
Phone: 814-865-7328
Email: bkgugino@psu.edu
Web: http://extension.psu.edu/plants/vegetable-fruit
TOMATO/POTATO EARLY BLIGHT WEEKLY UPDATE
The TOM-CAST disease forecasting model is a tool for helping tomato/potato growers decide when to
apply fungicides for managing early blight as well as Septoria leaf spot (tomato only). Below are the daily,
weekly and total summed disease severity values for 16 locations across Pennsylvania. The TOM-CAST
model is run using interpolated atmospheric weather data by ZedX, Inc. (not specific field-based weather
stations). Since environment varies, sometimes within relatively short distances, the spray
recommendation information should be considered in combination with your local environmental
conditions.
Seven additional locations (Sweden Valley, Butler, Loretto, Rock Springs, Ringtown, Gratz, Leola and
Landisville listed in the table reached the 35 cumulative DSV threshold to trigger the application of a
fungicide (Table 1). Please consult the 2013 Pennsylvania Vegetable Production Guide for specific product
and rate recommendations (http://extension.psu.edu/plants/vegetable-fruit/). Keep in mind that for
potato early blight inoculum is typically present in the field around July 4th. For earlier planted cultivars
this can coincide with the transition of the crop from flowering to tuber formation, a more susceptible
stage in the phenology of the crop. For tomatoes, once any fruit start to ripen, regular fungicide
applications may be warranted.
Table 1. Actual daily disease severity values (DSV) from June 25 through July 1, forecasted DSV for July 2
through July 5 and total accumulated DSVs since June 1, 2013 for 16 locations across Pennsylvania.
June daily DSVs
Town
County
25
26
27
28
29
30
1
Total
weekly
accum.
DSV
Forecasted Aug
DSVs
2
3
4
5
Total
accum.
DSV June
1 to July 1
Fairview
Erie
0
0
1
2
2
3
3
11
5
5
5
5
34
Corry
Erie
0
1
2
2
3
3
3
14
5
5
5
5
49
Sweden Valley
Potter
1
1
1
2
3
4
4
16
3
4
4
2
46
Butler
Butler
0
1
2
2
3
3
3
14
5
5
5
5
35
Finleyville
Washington
0
1
2
2
3
3
3
14
2
3
4
4
31
Loretto
Cambria
1
1
2
2
3
3
3
15
3
4
5
2
45
Rock Springs
Centre
1
1
2
2
3
3
3
15
3
4
4
1
37
Jersey Shore
Lycoming
0
1
1
1
3
3
3
12
3
4
4
1
23
Clarks Summit
Lackawanna
1
2
1
2
2
2
1
11
3
4
5
1
27
Wyoming Valley
Luzerne
1
2
0
1
2
2
2
10
3
4
5
1
28
Germansville
Lehigh
1
1
1
1
2
2
2
10
2
3
4
5
33
Kutztown
Berks
1
0
1
1
2
2
2
9
4
4
5
2
29
Ringtown
Schuylkill
1
2
2
2
2
2
2
13
4
4
5
1
40
Gratz
Dauphin
1
1
2
2
3
3
3
15
3
4
4
1
35
Leola
Lancaster
1
1
1
2
2
2
2
11
4
4
5
5
37
Landisville
Lancaster
2
2
2
2
2
2
2
14
3
4
4
4
41
----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, experimental, economic, legal, etc.) available to the user.
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