posted on July 29, 2009 14:11
Mary Hausbeck
Plant Pathology
Downy mildew on cucumbers has been found in several counties across the state this week. In general, the number of plants infected has been low, but given the continued cool, wet weather, it will not take long for the disease to spread and cause rapid blighting and plant death. It is crucial that growers to protect those crops that are most susceptible. It is clear that cucumbers and melons are most susceptible to downy mildew, but we are getting reports from other states that the other vine crops are also at some risk of developing downy mildew.
At this juncture, all cucumbers and melons across the state must be protected with fungicides immediately. Do not wait for disease to develop because then it may be too late. All other vine crops must be watched very closely for anything that is peculiar and samples should be brought to an extension office or to the MSU Diagnostic Services. Although the pumpkins, winter and summer squash, zucchini and gourds have not readily developed downy mildew in past years, this summer’s weather is not typical and is extremely favorable for downy mildew development. I do not want growers of pumpkins, squashes, etc. to believe that their crops are immune from downy mildew. All bets are off as a result of this weather!
Confirmed Downy Mildew Reports in Michigan
as of July 29
|
1
|
Monroe
|
7/13 cucumber (home garden)
7/23 cantaloupe (home garden)
|
|
2
|
Saginaw
|
7/14 commercial cucumber
|
|
3
|
Tuscola
|
7/14 commercial cucumber
|
|
4
|
Berrien
|
7/28 cucumber (untreated research plot)
|
|
5
|
Ingham
|
7/28 “Straight Eight” cucumber (sentinel)
|
|
6
|
St. Clair
|
7/28 commercial cucumber
|
|
7
|
Calhoun
|
7/28 cucumber (home garden)
|
8
|
Bay
|
7/29 commercial cucumber
|
9
|
Lenawee
|
7/29 cucumber (confirmed by M Hausbeck)
|
10
|
Allegan |
7/29 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
|
--
|
--
|
|
2
|
--
|
--
|
S0
|
2
|
8
|
S2
|
--
|
|
3
|
S15
|
S5
|
5
|
12
|
440
|
7
|
S15
|
|
4
|
3
|
2
|
2
|
2
|
465
|
0
|
7
|
|
5
|
5
|
2
|
3
|
3
|
100
|
2
|
10
|
|
6
|
2
|
20
|
5
|
10
|
60
|
0
|
18
|
|
7
|
7
|
12
|
0
|
3
|
28
|
2
|
3
|
|
8
|
2
|
0
|
0
|
5
|
0
|
0
|
3
|
|
9
|
3
|
2
|
7
|
12
|
5
|
7
|
8
|
|
10
|
40
|
3
|
2
|
0
|
7
|
8
|
12
|
|
11
|
5
|
0
|
3
|
0
|
8
|
0
|
5
|
|
12
|
7
|
2
|
18
|
8
|
7
|
8
|
2
|
|
13
|
2
|
0
|
3
|
8
|
8
|
2
|
2
|
|
14
|
2
|
5
|
2
|
18
|
27
|
13
|
10
|
|
15
|
7
|
5
|
7
|
2
|
8
|
5
|
13
|
|
16
|
8
|
3
|
2
|
7
|
15
|
0
|
13
|
|
17
|
0
|
0
|
0
|
0
|
2
|
0
|
3
|
|
18
|
3
|
3
|
7
|
7
|
2
|
12
|
3
|
|
19
|
3
|
0
|
23
|
2
|
3
|
5
|
2
|
|
20
|
2
|
5
|
2
|
7
|
7
|
0
|
5
|
|
21
|
8
|
10
|
7
|
3
|
3
|
15
|
12
|
|
June 22
|
17
|
10
|
0
|
13
|
10
|
5
|
2
|
|
23
|
2
|
3
|
23
|
2
|
12
|
3
|
7
|
|
24
|
5
|
5
|
10
|
3
|
5
|
2
|
8*
|
|
25
|
2
|
3
|
5
|
3
|
7
|
0
|
2
|
|
26
|
5
|
2
|
10
|
7
|
8
|
0
|
0
|
|
27
|
10
|
3
|
13
|
8
|
3
|
7
|
5
|
|
28
|
25
|
3
|
3
|
2
|
0
|
3
|
5*
|
|
29
|
23
|
8
|
2
|
2
|
5
|
7
|
2*
|
|
30
|
7
|
0
|
2
|
2
|
2
|
25
|
3
|
|
July 1
|
2
|
0
|
5
|
22
|
10
|
78
|
3
|
|
2
|
2
|
5
|
13
|
0
|
10
|
5
|
7
|
|
3
|
3
|
2
|
12
|
0
|
8
|
8
|
3
|
|
4
|
2
|
3
|
27
|
10
|
2
|
12
|
5
|
|
5
|
0
|
3
|
23
|
7
|
20
|
22
|
5
|
|
6
|
5
|
0
|
15
|
10
|
12
|
15
|
7
|
|
7
|
7
|
0
|
5
|
7
|
8
|
7
|
3
|
|
8
|
12
|
2*
|
3
|
2
|
5
|
23
|
0
|
|
9
|
15
|
2*
|
5
|
7
|
3
|
35
|
0*
|
|
10
|
8
|
0*
|
5
|
0
|
0
|
12
|
2*
|
|
11
|
8
|
0*
|
0♦
|
0
|
0
|
0
|
0*
|
|
12
|
8
|
5*
|
2♦
|
2
|
0
|
13
|
5
|
|
13
|
8
|
0*
|
0♦
|
3
|
2DM
|
8
|
5*
|
|
14
|
23
|
12*
|
0
|
2
|
2
|
3DM
|
3*
|
|
15
|
15
|
20
|
2
|
0
|
0*
|
12
|
3
|
|
16
|
28
|
8
|
25
|
18
|
7
|
18
|
8
|
|
17
|
7
|
8
|
7
|
10
|
2
|
13
|
0
|
|
18
|
5
|
7
|
3
|
3
|
2
|
55
|
0
|
|
19
|
8
|
3
|
2
|
5
|
5
|
42
|
0
|
|
20
|
22
|
20
|
7
|
3
|
3
|
0
|
2
|
|
21
|
32
|
23
|
12
|
2
|
2
|
2*
|
10
|
|
22
|
|
|
2
|
3
|
3
|
8
|
|
|
23
|
|
|
3
|
|
|
5
|
|
SSpore trapping started on this date. *Spores present but soil prevented accurate count.
ESpore trapping ended on this date. ♦Spore trap stopped. DMDisease was found in the county on this date. ‡Partial day.
CUCUMBER
|
APPLIED BEFORE DISEASE
(7-day intervals)
|
|
APPLIED AFTER DISEASE
(5-day intervals)
|
|
|
|
|
|
|
|
- Previcur Flex 6SC (2 day PHI)
|
- Previcur Flex 6SC (2 day PHI)
|
|
|
|
|
|
|
|
|
|
|
|
Alternate products and mix each with either:
- Dithane (mancozeb) 3 lb or
- Bravo (chlorothalonil) 1.5 pt
|
|
Alternate products and mix each with either:
- Dithane (mancozeb) 3 lb or
- Bravo (chlorothalonil) 2 pt
|
VINE CROPS, such as zucchini, squash, pumpkin, melon and gourds
|
APPLIED BEFORE DISEASE
(7- to 10-day intervals)
|
|
APPLIED AFTER DISEASE
(7-day intervals)
|
|
|
|
|
|
|
|
- Previcur Flex 6SC (2 day PHI)
|
- Previcur Flex 6SC (2 day PHI)
|
|
|
|
|
|
|
|
|
|
|
|
Alternate products and mix each with either:
- Dithane (mancozeb) 3 lb or
- Bravo (chlorothalonil) 1.5 pt
|
|
Alternate products and mix each with either:
- Dithane (mancozeb) 3 lb or
- Bravo (chlorothalonil) 2 pt
|
[Please note: Gavel 75WG and Dithane are not registered on some vine crops.]