Potato Disease Advisory #17 – July 15, 2011

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Location: Art and Keith Wicks Farm, Rt 9, Little Creek, Kent County.
Greenrow: May 3

Date

Late Blight

Early Blight

Spray Interval Recommendation

DSV

Total DSV

Accumulated P-days*

6/27

1

70

416

10-days
6/28

1

71

424

10-days
6/29

0

71

432

10-days
6/29-7/2

0

71

456

10-days
7/3

1

72

462

10-days
7/4

0

72

468

10-days
7/5

1

73

474

10-days
7/6

0

73

481

10-days
7/7

3

76

486

7-days
7/8

3

79

493

5-days
7/9

0

79

499

5-days
7/10

0

79

506

5-days
7/11-7/14

0

79

530

10-days

 

Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight. The recent rains and the amount of humidity we have been having have made conditions for late blight more favorable. Maintain spray programs if plants are still growing. The shortened spray interval reflects the more favorable conditions and is a very conservative recommendation but with no recent detections, 7-day intervals should be fine.

Late Blight was reported two weeks ago in DE, on the eastern shore VA, and Long Island, New York. There have been no further reports of late blight in DE or VA but late blight has been reported on the North Fork on Long Island, NY in addition to the earlier find on the South Fork.

For specific fungicide recommendations, see the 2011 Delaware Commercial Vegetable Production Recommendations Book.

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