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Models: Disease Severity Table

Modified DSV Table: Hours of leaf wetness required for DSV accumulations 1-4
Mean temperature (C)
during leaf wetness
Hours of leaf wetness

13-17 0-6 7-15 16-20 21+
18-20 0-3 4-8 9-15 16-22 23+
21-25 0-2 3-5 6-12 13-20 21+
26-29 0-3 4-8 9-15 16-22 23+

DSV 0 1 2 3 4

Table from Madden L., Pennypacker, S. P., and McNab, A. A. 1978. FAST, a forecast system for Alternaria solani on tomato. Phytopathology 68:1354-1358.

Disease severity values (DSV) are calculated as a function of hours of leaf wetness and average air temperature during leaf wetness. The DSV is based on the FAST early blight model of tomato. After treatment, the DSV accumulations reset to zero.

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