Posts Tagged ‘potato late blight’

Potato Disease Advisory #20 – July 19, 2012

Friday, July 20th, 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.

Potato Disease Advisory #19 – July 12, 2012

Thursday, July 12th, 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

6/4-6/6

0

71

355

10-days

6/7-6/11

0

71

395

10-days

6/11-6/14

8

79

424

7-days

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

 

The spray interval recommendation is 10 days. The hot and dry weather we continue to experience should reduce the threat of late blight. There have been no reports in Delaware. Visit http://www.usablight.org/ to see where late blight has been found on potato and tomato in the region.

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

Potato Disease Advisory #18 – July 6, 2012

Friday, July 6th, 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

6/4-6/6

0

71

355

10-days

6/7-6/11

0

71

395

10-days

6/11-6/14

8

79

424

7-days

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

 

The spray interval recommendation is 10 days. The hot and dry weather we continue to experience should reduce the threat of late blight. There have been no reports in Delaware. Visit http://www.usablight.org/ to see where late blight has been found on potato and tomato in the region.

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

Potato Disease Advisory #16 – June 28, 2012

Friday, June 29th, 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

5/24-5/28

8

65

279

5-days

5/28-5/30

3

68

294

5-days

5/31-6/3

3

71

331

7-days

6/4-6/6

0

71

355

10-days

6/7-6/11

0

71

395

10-days

6/11-6/14

8

79

424

7-days

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

 

The spray interval recommendation has been set at 10 days. The hot and dry weather we are experiencing should reduce the threat of late blight. There have been no reports in Delaware. Visit http://www.usablight.org/ to see where late blight has been found on potato and tomato in the region.

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

Potato Disease Advisory #14 – June 21, 2012

Friday, June 22nd, 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

5/20-5/22

11

55

229

5-days

5/22-5/23

2

57

238

5-days

5/24-5/28

8

65

279

5-days

5/28-5/30

3

68

294

5-days

5/31-6/3

3

71

331

7-days

6/4-6/6

0

71

355

10-days

6/7-6/11

0

71

395

10-days

6/11-6/14

8

79

424

7-days

6/15-6/18

0

79

460

10-days

6/19-6/20

1

80

474

10-days

 

The spray interval recommendation has been set at 10 days. The hot and dry weather we are experiencing should reduce the threat of late blight. There are no reports in Delaware. Visit http://www.usablight.org/ to see where late blight has been found on potato and tomato in the region.

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

Potato Disease Advisory #12 – June 15, 2012

Friday, June 15th, 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

5/20-5/22

11

55

229

5-days

5/22-5/23

2

57

238

5-days

5/24-5/28

8

65

279

5-days

5/28-5/30

3

68

294

5-days

5/31-6/3

3

71

331

7-days

6/4-6/6

0

71

355

10-days

6/7-6/11

0

71

395

10-days

6/11-6/14

8

79

424

7-days

 

The spray interval recommendation has been lowered to 7 days. Rainfall and high humidity earlier in the week made conditions for late blight more favorable. The forecast is predicting sunny and dry weather, which should make conditions less favorable.  There are no reports of late blight in Delaware.

Continue to scout for late blight symptoms in local potato fields. Please notify and submit samples with symptoms to your local county extension office (Kent: 302-730-4000, Sussex: 302-856-7303) or contact the UD Plant Diagnostic clinic (302-831-1390) to have the sample confirmed. You may also email Nancy Gregory at ngregory@udel.edu or Phillip Sylvester at phillip@udel.edu if you have a sample to submit.

Late blight has been found in the region. You can monitor where late blight is showing up by visiting the USA blight website at: http://www.usablight.org/?q=map. Confirmations of late blight on potato and tomato are tracked and added to the map as they are reported.

Early Blight
A total of 424 P-days have accumulated at this site as of Thursday, June 14. Protectant fungicide applications targeted at early blight are recommended at this time. Commercial fungicide recommendations can be found in the 2012 Delaware Commercial Vegetable Recommendations Guide at http://ag.udel.edu/extension/vegprogram/pdf/potatoes.pdf

Potato Disease Advisory #10 – June 7, 2012

Friday, June 8th, 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

5/20-5/22

11

55

229

5-days

5/22-5/23

2

57

238

5-days

5/24-5/28

8

65

279

5-days

5/28-5/30

3

68

294

5-days

5/31-6/3

3

71

331

7-days

6/4-6/6

0

71

355

10-days

 

The spray interval recommendation is now 10 days. The forecast is predicting warm and dry weather which should reduce the threat. Late blight has been reported in Virginia and Pennsylvania over the past seven days. The map below shows confirmed reports of late blight. The red shaded areas indicate the report was made in the past seven days while the blue shaded areas indicate an older report (more than seven days ago). You can visit this map at http://www.usablight.org/. There have been no reports of late blight in Delaware this year.

Continue to scout for late blight symptoms in local potato fields. Please notify and submit samples with symptoms to your local county extension office (Kent: 302-730-4000 Sussex: 302-856-7303) or contact the UD Plant Diagnostic clinic (302-831-1390) to have the sample confirmed. You may also email Nancy Gregory at ngregory@udel.edu or Phillip Sylvester at phillip@udel.edu if you have a sample to submit.

Early Blight
A total of 355 P-days have accumulated at this site as of Wednesday, June 6. Protectant fungicide applications targeted at early blight are recommended at this time. Commercial fungicide recommendations can be found in the 2012 Delaware Commercial Vegetable Recommendations Guide at http://ag.udel.edu/extension/vegprogram/pdf/potatoes.pdf.

Potato Disease Advisory #8 – May 31, 2012

Friday, June 1st, 2012

Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu and Nancy Gregory, Plant Diagnostician; ngregory@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

4/20-4/30

12

12

None

4/30-5/1

8

20

7-days

5/1-5/8

15

35

5-days

5/8-5/10

4

39

5-days

5/10-5/13

0

39

149

10-days

5/13-5/16

5

44

177

7-days

5/17-5/20

0

44

209

7-days

5/20-5/22

11

55

229

5-days

5/22-5/23

2

57

238

5-days

5/24-5/28

8

65

279

5-days

5/28-5/30

3

68

294

5-days

 

The threshold of 18 DSV’s has been exceeded. Sixty-eight (68) DSVs have accumulated as of Wednesday, May 30. This includes any potatoes that established green row (approximately 50% emergence) prior to and on April 20. An additional three (3) DSVs accumulated from Monday, May 28 to Wednesday, May 30. The spray interval recommendation is 5 days.

Continue to scout for Late blight symptoms in local potato fields. Please notify and submit samples with symptoms to your local county extension office (Kent: 302-730-4000, Sussex: 302-856-7303) or contact the UD Plant Diagnostic clinic (302-831-1390) to have the sample confirmed. You may also email Nancy Gregory at ngreogry@udel.edu or Phillip Sylvester at phillip@udel.edu if you have a sample to submit.

Good coverage with preventative fungicides application is very important for Late blight control. Commercial fungicide recommendations can be found in the 2012 Delaware Commercial Vegetable Recommendations Guide at http://ag.udel.edu/extension/vegprogram/pdf/potatoes.pdf

Early Blight
We are using the predictive model WISDOM to determine the first fungicide application for prevention of early blight. The model predicts the first seasonal rise in the number of spores of the early blight fungus based on the accumulation of 300 physiological days (a type of degree-day unit, referred to as P-days) from green row. A total of 294 P-days have accumulated at this site as of Wednesday, May 30. Airborne Early blight inoculum should rise 5-10 days after accumulating 300 P-days. Judging by the forecast, the 300-P day threshold will probably be exceeded in a day or two. A protectant fungicide application should be made once we exceed that threshold. Commercial fungicide recommendations can be found in the 2012 Delaware Commercial Vegetable Recommendations Guide at http://ag.udel.edu/extension/vegprogram/pdf/potatoes.pdf

Potato Disease Advisory #6 – May 24, 2012

Thursday, May 24th, 2012

Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu and Nancy Gregory, Plant Diagnostician; ngregory@udel.edu

LATE BLIGHT ON POTATO ALERT:
From Andy Wyenandt, Extension Vegetable Pathologist, Rutgers University: Late blight was confirmed on actively sporulating leaf lesions from an 8 acre potato field in Burlington County, New Jersey. The few infected plants were found at the end of a row where the boom sprayer was most likely turned off. The grower had preventative applications of manzate followed by chlorothalonil prior. Seed pieces were sourced from Maine. This is the first report of Late blight in New Jersey on potato or tomato this year.

Continue to scout for Late blight symptoms in local potato fields. Please notify and submit samples with symptoms to your local county extension office (Kent: 302-730-4000 Sussex: 302-856-7303) or contact the UD Plant Diagnostic clinic (302-831-1390) to have the sample confirmed. You may also email Nancy Gregory at ngreogry@udel.edu or Phillip Sylvester at phillip@udel.edu if you have a sample to submit.

Good coverage with preventative fungicides application is very important for Late blight control. Commercial fungicide recommendations can be found in the 2012 Delaware Commercial Vegetable Recommendations Guide at http://ag.udel.edu/extension/vegprogram/pdf/potatoes.pdf

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

Date

DSV

Total DSV

Accumulated P-Days

Spray Interval Recommendations

4/20 – 4/30

12

12

None

4/30 – 5/1

8

20

7-days

5/1 – 5-8

15

35

5-days

5/8 – 5/10

4

39

5-days

5/10 – 5/13

0

39

149

10-days

5/13 – 5/16

5

44

177

7-days

5/17-5/20

0

44

209

7-days

5/20-5/22

11

55

229

5-days

5/22-5/23

2

57

238

5-days

The threshold of 18 DSVs has been exceeded. Fifty-seven (57) DSVs have accumulated as of Wednesday, May 23. This includes any potatoes that established green row (approximately 50% emergence) prior to and on April 20. An additional thirteen (13) DSVs accumulated from Sunday, May 20 to Wednesday, May 23. Recent weather conditions have been favorable for late blight development since the last report. The predicted hot weather would make conditions less favorable for Late blight. The spray interval recommendation has been lowered to 5 days.

Early Blight
We are using the predictive model WISDOM to determine the first fungicide application for prevention of early blight. The model predicts the first seasonal rise in the number of spores of the early blight fungus based on the accumulation of 300 physiological days (a type of degree-day unit, referred to as P-days) from green row. A total of 238 P-days have accumulated at this site as of Wednesday, May 23. Once 300 P-days have accumulated, the first fungicide for early blight control should be applied. This usually occurs when rows are touching.

Spray to Prevent Late Blight on Potato and Tomato

Thursday, May 24th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Late blight has been found on potato in central New Jersey. The grower was applying preventative fungicides, however lesions occurred in a part of the field that the sprayer missed. All potato and tomato crops are susceptible to this disease. Growers should scout and apply preventative fungicides to protect their crops. Chlorothalonil, mancozeb or Polyram can be applied to potato and chlorothalonil, Gavel, or mancozeb can be applied to tomato. Complete coverage of the field is extremely important. Once late blight has been found close to a grower’s field, switch to a fungicide that is late blight specific. More information on available fungicides for this disease can be found at http://ag.udel.edu/extension/vegprogram/publications.htm#vegrecs.

Controlling late blight in organic systems is extremely difficult. Organic growers should apply a protectant such as copper to their crop. Serenade, Sonata and Sporatec are OMRI listed, and labeled for late blight. (However, there are very few research trials on efficacy of these products). It is critical to apply these materials with adequate coverage and at short spray intervals.