PENNSYLVANIA VEGETABLE DISEASE UPDATE
JULY 23, 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: [email protected]
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.
Within the last couple of weeks, all 16 locations listed in the table reached the 35 cumulative DSV
threshold to trigger the application of a fungicide. Subsequent fungicides can be applied based on the
accumulation of an additional 18 DSVs. 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 July 16 through July 22, forecasted DSV for July 23
through 26 and total accumulated DSVs since June 1, 2013 for 16 locations across Pennsylvania.
July daily DSVs
Town
County
16
17
18
19
20
21
22
Total
weekly
accum.
DSV
Forecasted Aug
DSVs
23
24
25
26
Total
accum.
DSV June
1 to July
22
Fairview
Erie
0
0
1
1
1
2
0
5
2
3
0
0
49
Corry
Erie
3
3
3
3
3
3
3
21
3
3
0
0
112
Sweden Valley
Potter
1
1
1
1
2
1
1
8
2
1
0
0
104
Butler
Butler
1
1
3
3
3
3
3
17
4
4
0
0
75
Finleyville
Washington
0
1
2
2
1
2
2
10
3
4
0
0
61
Loretto
Cambria
1
1
1
1
1
0
1
6
3
2
0
0
96
Rock Springs
Centre
0
0
1
1
1
0
1
4
3
3
0
0
67
Jersey Shore
Lycoming
1
1
1
1
1
0
0
5
3
3
0
0
59
Clarks Summit
Lackawanna
0
0
0
1
0
0
0
1
3
3
0
0
45
Wyoming Valley
Luzerne
0
0
0
0
0
0
0
0
3
3
0
0
46
Germansville
Lehigh
2
0
0
1
1
1
1
6
3
3
0
0
74
Kutztown
Berks
1
0
0
0
0
1
0
2
3
3
0
0
54
Ringtown
Schuylkill
2
2
1
1
1
1
2
10
3
3
0
0
86
Gratz
Dauphin
4
4
1
1
1
0
1
12
3
3
0
0
82
Leola
Lancaster
2
1
0
0
0
1
0
4
3
3
0
0
66
Landisville
Lancaster
1
0
0
0
0
1
0
2
3
3
0
0
67
----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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