Fruit IPMin Michigan
Fruit IPM
in Michigan
The Mills Table is used to predict Apple scab infections. It is also useful in predicting pear scab a similar disease. The number of hours of leaf wetness required for infection decreases as the temperature increases. Optimum conditions occur when temperatures are 60 and 76 F with 9 hours of leaf wettness required for infection. Sprays with fungicides show be timed to control infections with the assumption that the infection began at the beginning of the rain.
Approximate numbers of hours of wetting required for primary apple scab infection at different air temperatures1 |
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Degree of Infection |
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Temperature Average ( ° F) |
Light (hrs.2) |
Moderate (hrs.) |
Heavy (hrs.) |
Incubation Period (days) |
78 |
13 |
17 |
26 |
- |
77 |
11 |
14 |
21 |
- |
76 |
9.5 |
12 |
19 |
- |
63 to 75 |
9 |
12 |
18 |
9 |
62 |
9 |
12 |
19 |
10 |
61 |
9 |
13 |
20 |
10 |
60 |
9.5 |
13 |
20 |
11 |
59 |
10 |
13 |
21 |
12 |
58 |
10 |
14 |
21 |
12 |
57 |
10 |
14 |
22 |
13 |
56 |
11 |
15 |
22 |
13 |
55 |
11 |
16 |
24 |
14 |
54 |
11.5 |
16 |
24 |
14 |
53 |
12 |
17 |
25 |
15 |
52 |
12 |
18 |
26 |
15 |
51 |
13 |
18 |
27 |
16 |
50 |
14 |
19 |
29 |
16 |
49 |
14.5 |
20 |
30 |
17 |
48 |
15 |
20 |
30 |
17 |
47 |
15 |
23 |
35 |
- |
46 |
16 |
24 |
37 |
- |
45 |
17 |
26 |
40 |
- |
44 |
19 |
28 |
43 |
- |
43 |
21 |
30 |
47 |
- |
42 |
23 |
33 |
50 |
- |
41 |
26 |
37 |
53 |
- |
40 |
29 |
41 |
56 |
- |
39 |
33 |
45 |
60 |
- |
38 |
37 |
50 |
64 |
- |
37 |
41 |
55 |
68 |
- |
33 to 36 |
48 |
72 |
96 |
- |
1
From W. 0. Mills, Cornell University; modified by A. L. Jones.Return to Apple Page, Fruit IPM Page, or Pear Page.
