Potato Disease Advisory #20 – July 19, 2012

Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Late blight Advisory
Location: Art and Keith Wicks Farm, Rt 9, Leipsic, Kent County, Delaware
Greenrow: April 20

Date

DSV

Total DSV

Accumulated
P-Days

Spray Interval Recommendation

6/15-6/18

0

79

460

10-days

6/19-6/21

1

80

478

10-days

6/22-6/25

2

82

507

10-days

6/25-6/27

0

82

524

10-days

6/28-7/2

0

82

549

10-days

7/3-7/5

0

82

561

10-days

7/6-7/11

0

82

593

10-days

7/12-7/18

2

84

632

10-days

The spray interval recommendation is 10 days. The hot and dry weather we experienced earlier in the week should reduce the threat of late blight. The weather is forecast to change with lower temperatures and possible thundershowers. Maintain spray programs if the plants are still growing. There have been no reports in Delaware and no recent reports of late blight on potato in the region. Visit http://www.usablight.org/ to see where late blight has been found on potato and tomato.

Commercial fungicide recommendations can be found in the 2012 Delaware Commercial Vegetable Recommendations Guide at http://ag.udel.edu/extension/vegprogram/pdf/potatoes.pdf.

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