posted on July 15, 2009 14:48
Mary Hausbeck, Plant Pathology
Downy mildew has been confirmed in three Michigan counties over the last 48 hours. They include Monroe, Saginaw and Tuscola. The Monroe sample came from a homeowner’s garden while the other samples are from commercial growers. All of the samples are from cucumbers. The spore counts across the state continue to indicate that the cucumber growing areas are being exposed to airborne downy mildew sporangia. As recommended earlier, all cucumber growers in the state should be spraying for downy mildew. I am recommending this because the spore traps clearly show that airborne sporangia are present and the weather continues to be cooler than normal with evening dews being especially favorable for downy mildew development. Keep in mind that overcast days with high humidity offer a good opportunity for the downy mildew to be transported from one field to another and certainly from one region to another.
Other cucurbits that may be especially at risk include melons (watermelons and cantaloupe). At this point, pumpkins, summer squash, zucchini, gourds, and winter squash should be monitored carefully with any unusual symptoms brought into campus for diagnosis.
Up-to-date information on cucurbit downy mildew is also available at Mary’s “For Growers” web page: http://plantpathology.msu.edu/labs/hausbeck/ForGrowers.html.
Confirmed Downy Mildew Reports in Michigan as of July 14
|
1
|
Monroe-- home garden
|
|
2
|
Saginaw -- 7/14 commercial cucumber
|
|
3
|
Tuscola -- 7/14 commercial cucumber
|
Table 1. Downy mildew spore trap daily totals (counts/m3/day) by location
|
Date
|
Michigan counties
|
|
E. Allegan
|
W. Allegan
|
Bay
|
Dundee
|
Monroe
|
Saginaw
|
VanBuren
|
|
June 1
|
--
|
--
|
--
|
S0
|
S8
|
--
|
--
|
|
June 2
|
--
|
--
|
S0
|
2
|
8
|
S2
|
--
|
|
June 3
|
S15
|
S5
|
5
|
12
|
440
|
7
|
S15
|
|
June 4
|
3
|
2
|
2
|
2
|
465
|
0
|
7
|
|
June 5
|
5
|
2
|
3
|
3
|
100
|
2
|
10
|
|
June 6
|
2
|
20
|
5
|
10
|
60
|
0
|
18
|
|
June 7
|
7
|
12
|
0
|
3
|
28
|
2
|
3
|
|
June 8
|
2
|
0
|
0
|
5
|
0
|
0
|
3
|
|
June 9
|
3
|
2
|
7
|
12
|
5
|
7
|
8
|
|
June 10
|
40
|
3
|
2
|
0
|
7
|
8
|
12
|
|
June 11
|
5
|
0
|
3
|
0
|
8
|
0
|
5
|
|
June 12
|
7
|
2
|
18
|
8
|
7
|
8
|
2
|
|
June 13
|
2
|
0
|
3
|
8
|
8
|
2
|
2
|
|
June 14
|
2
|
5
|
2
|
18
|
27
|
13
|
10
|
|
June 15
|
7
|
5
|
7
|
2
|
8
|
5
|
13
|
|
June 16
|
8
|
3
|
2
|
7
|
15
|
0
|
13
|
|
June 17
|
0
|
0
|
0
|
0
|
2
|
0
|
3
|
|
June 18
|
3
|
3
|
7
|
7
|
2
|
12
|
3
|
|
June 19
|
3
|
0
|
23
|
2
|
3
|
5
|
2
|
|
June 20
|
2
|
5
|
2
|
7
|
7
|
0
|
5
|
|
June 21
|
8
|
10
|
7
|
3
|
3
|
15
|
12
|
|
June 22
|
17
|
10
|
0
|
13
|
10
|
5
|
2
|
|
June 23
|
2
|
3
|
23
|
2
|
12
|
3
|
7
|
|
June 24
|
5
|
5
|
10
|
3
|
5
|
2
|
8*
|
|
June 25
|
2
|
3
|
5
|
3
|
7
|
0
|
2
|
|
June 26
|
5
|
2
|
10
|
7
|
8
|
0
|
0
|
|
June 27
|
10
|
3
|
13
|
8
|
3
|
7
|
5
|
|
June 28
|
25
|
3
|
3
|
2
|
0
|
3
|
5*
|
|
June 29
|
23
|
8
|
2
|
2
|
5
|
7
|
2*
|
|
June 30
|
7
|
0
|
2
|
2
|
2
|
25
|
3
|
|
July 1
|
2
|
0
|
5
|
22
|
10
|
78
|
3
|
|
July 2
|
2
|
5
|
13
|
0
|
10
|
5
|
7
|
|
July 3
|
3
|
2
|
12
|
0
|
8
|
8
|
3
|
|
July 4
|
2
|
3
|
27
|
10
|
2
|
12
|
5
|
|
July 5
|
0
|
3
|
23
|
7
|
20
|
22
|
5
|
|
July 6
|
5
|
0
|
15
|
10
|
12
|
15
|
7
|
|
July 7
|
7
|
0
|
5
|
7
|
8
|
7
|
3
|
|
July 8
|
|
|
|
2
|
5
|
23
|
|
|
July 9
|
|
|
|
7
|
3
|
|
|
|
July 10
|
|
|
|
0
|
0
|
|
|
|
July 11
|
|
|
|
0
|
0
|
|
|
|
July 12
|
|
|
|
2
|
0
|
|
|
Table 2. Fungicide recommendations
[Please note: Gavel 75WG and Dithane are not registered on some vine crops.]