Posts Tagged ‘potato disease update’

Potato Disease Advisory #3 – May 17, 2012

Friday, May 18th, 2012

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

Date DSV Total DSV 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 10-days
5/13 – 5/16 5 44 7-days

The threshold of 18 DSVs has been exceeded. Forty-four (44) DSVs have accumulated as of Thursday, May 17. This includes any potatoes that established green row (approximately 50% emergence) prior to and on April 20. An additional five (5) DSVs accumulated during the recent wet, cloudy weather earlier in the week. While the spray interval has been lowered, the short-term forecast is predicting ample sunshine and warm temperatures. This should reduce the risk of late blight development.

Potato Disease Advisory #1 – May 10, 2012

Friday, May 11th, 2012

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu; Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

With my impending retirement only a week away, we were concerned that the Potato Disease Advisory email and FAX may not get done this year and would resume hopefully by my replacement. Phillip Sylvester, our Kent County Ag Agent, has volunteered to keep the late blight advisory part of the report operating for potato growers in our area for this season.

Late blight Advisory
We are using the E-WEATHER SERVICE from SkyBit, Inc as we have in the past. The service determines specific requested weather parameters (temperature, relative humidity and rainfall) based on calculations of data from the nearest National Weather Service stations. This weather data is used in the WISDOM software program for predicting late blight and early blight and making spray recommendations. Our location this year is:

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

Date DSV Total DSV 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

The threat of late blight from seed infection was moderate since there was late blight in 2011 in the seed producing areas. Be vigilant since we have exceeded 18 DSVs already for 2012. The first late blight fungicide application is recommended once 18 Disease Severity Values (DSVs) accumulate from green row. Green row occurred on approximately April 20 at this location. Please be vigilant and keep a look out for suspect infections on young plants coming from infected seed pieces! Growers opting not to use the forecast system should put the first late blight fungicide application on when the plants are 6 inches tall or plants are touching down the row, and repeat every 7 days. There are numerous fungicides now labeled for late blight control; however, use of mancozeb (Manzate, Penncozeb, or Dithane) or chlorothalonil (Bravo) are still very effective early season protective fungicides to use. See the 2012 Commercial Vegetable Production Recommendations-Delaware for more information on products and rates.

The threshold of 18 DSVs has been exceeded. Thirty-five (35) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since April 20. Spraying as soon as possible with a protectant fungicide would be advised if not already on a spray program. The forecast looks like favorable weather for late blight will continue. Scout your fields regularly for symptoms. Late blight was reported in northern North Carolina last week.

Potato Disease Advisory #18 – July 19, 2011

Thursday, July 21st, 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
7/15-7/18

0

79

558

10-days

 

Continue to scout fields for symptoms of late blight. Maintain spray programs if plants are still growing.

There have been no further reports of late blight in the region.

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

Potato Disease Advisory #17 – July 15, 2011

Friday, July 15th, 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.

Potato Disease Advisory #15 – July 7, 2011

Friday, July 8th, 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*
6/16 1 67 328 7-days
6/17 0 67 336 7-days
6/18-6/19 0 67 352 10-days
6/20-6/22 1 68 377 10-days
6/23 1 69 383 10-days
6/24-6/26 0 69 407 10-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

Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight. Continued dry weather will not favor the spread of late blight.

Late Blight was reported last week 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.

 

Potato Disease Advisory #12 – June 30, 2011

Friday, July 1st, 2011

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

Late blight Advisory

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*
6/13 0 66 301 7-days
6/13-6/15 0 66 318 7-days
6/16 1 67 328 7-days
6/17 0 67 336 7-days
6/18-6/19 0 67 352 10-days
6/20-6/22 1 68 377 10-days
6/23 1 69 383 10-days
6/24-6/26 0 69 407 10-days
6/27 1 70 416 10-days
6/28 1 71 424 10-days

 

Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight. We have surpassed the 300 P-day threshold for initiating early blight sprays.

Late Blight was reported this week in DE, on the eastern shore VA, and Long Island, New York. The weather conditions have been favorable the past few days but the hot weather forecasted for this weekend should help reduce the threat. The Delaware find near Leipsic in Kent County was a small area at the end of a field next to woods and under power lines that obstructed the aerial application of fungicide applied to the whole field. Late blight specific fungicide has been applied.

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

 

Potato Disease Advisory #10 – June 23, 2011

Friday, June 24th, 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
6/6 1 58 251 10-days
6/6-6/8 0 58 263 10-days
6/8-6/9 0 58 267 10-days
6/10 2 60 274 10-days
6/11 4 64 282 5-days
6/12 2 66 291 5-days
6/13 0 66 301 7-days
6/13-6/15 0 66 318 7-days
6/16 1 67 328 7-days
6/17 0 67 336 7-days
6/18-6/19 0 67 352 10-days
6/20-6/22 0 67 377 10-days

 

Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight. We have surpassed the 300 P-day threshold for initiating early blight sprays.

Early Blight and Black Dot
Many fields have flowered and this is a good time to consider switching to an application or two of Gem, Headline, Quadris, or Evito (no black dot label) for early blight susceptible varieties. This can also be helpful for late season varieties including russets if stress makes plants susceptible to black dot later. Make one or two applications at the end of flowering and repeat 14 days later. Apply mancozeb or chlorothalonil 7-days later between the two applications. Another product that is labeled for early blight is Revus Top from Syngenta. Revus Top is a combination product of Revus (mandipropamid, Group 40) plus difenoconazole which is triazole fungicide (Group 3). Difenconazole has been used in Europe very successfully for early blight control. Since it is a different mode of action than the strobilurin fungicides (Group 11) it would be a good alternative if resistance is an issue if Gem, Quadris, or Headline are not controlling early blight.

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

 

Potato Disease Advisory #8 – June 13, 2011

Friday, June 17th, 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*
5/27-5/28 2 54 175 5-days
5/28-5/29 2 56 183 7-days
5/29-5/30 1 57 191 5-days
5/30 0 57 197 7-days
5/31-6/1 0 57 207 10-days
6/1-6/5 0 57 232 10-days
6/6 1 58 251 10-days
6/6-6/8 0 58 263 10-days
6/8-6/9 0 58 267 10-days
6/10 2 60 274 10-days
6/11 4 64 282 5-days
6/12 2 66 291 5-days
6/13 0 66 301 7-days

 

Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight. We have reached the 300 P-day threshold for initiating early blight sprays.

P days
We use the predictive model WISDOM to determine the first fungicide application for prevention of early blight as well. 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. To date, 301 P-days have accumulated at the site. Once 300 P-days have accumulated, the first fungicide for early blight control should be applied. This usually occurs when rows are touching.

If pink rot or leak is a concern and no pink rot fungicide was applied at planting consider applying one of the following when potatoes are nickel-sized and repeating 14 days later. Apply in as much water as possible (20-30 gal/A): Mefanoxam/chlorothalonil (Ridomil/Bravo) 2 lb/A, or Ridomil Gold/MZ 2.5 lb/A, or Ridomil Gold/Copper 2 lb/A. If Platinum/ Ridomil Gold was applied at planting the label allows one foliar application of one of those products at tuber initiation if conditions warrant. Presidio was also labeled this spring for pink rot.

 

Potato Disease Advisory #7 – June 9, 2011

Friday, June 10th, 2011

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

Late Blight Advisory

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*
5/27-5/28 2 54 175 5-days
5/28-5/29 2 56 183 7-days
5/29-5/30 1 57 191 5-days
5/30 0 57 197 7-days
5/31-6/1 0 57 207 10-days
6/1-6/5 0 57 232 10-days
6/6 1 58 251 10-days
6/6-6/8 0 58 263 10-days

 

The forecasted hot weather will reduce the risk and slow any development of late blight. Continue to scout fields for symptoms of late blight. Conditions will continue to favor early blight with the increased temperatures and high humidity. Heat stress will make the oldest leaves more susceptible. We should reach 300 P-days this weekend.

P days
We use the predictive model WISDOM to determine the first fungicide application for prevention of early blight as well. 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. To date, 263 P-days have accumulated at the site. Once 300 P-days have accumulated, the first fungicide for early blight control should be applied. This usually occurs when rows are touching.

If pink rot or leak is a concern and no pink rot fungicide was applied at planting consider applying one of the following when potatoes are nickel-sized and repeating 14 days later. Apply in as much water as possible (20-30 gal/A): Mefanoxam/chlorothalonil (Ridomil/Bravo) 2 lb/A, or Ridomil Gold/MZ 2.5 lb/A, or Ridomil Gold/Copper 2 lb/A. If Platinum/ Ridomil Gold was applied at planting the label allows one foliar application of one of those products at tuber initiation if conditions warrant. Presidio was also labeled this spring for pink rot control. The label uses for pink rot control include an in-furrow application at planting with a follow-up application between hilling and tuber initiation. There is no labeled use for a foliage application for pink rot control. It is labeled for late blight control at 4.0 fl oz/A.

 

Potato Disease Advisory #5 – June 2, 2011

Friday, June 3rd, 2011

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

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

Date DSV Total DSV Accumulated P-days* Spray Interval Recommendation
5/19-5/21 5 38 5-days
5/21-5/23 12 50 5-days
5/23-5/24 2 52 5-days
5/24-5/25 0 52 5-days
5/27-5/28 2 54 175 5-days
5/28-5/29 2 56 183 7-days
5/29-5/30 1 57 191 5-days
5/30 0 57 197 7-days
5/31-6/1 0 57 207 10-days

The dry weather and the recent high temperatures will reduce the risk and slow any development of late blight. Continue to scout fields for symptoms of late blight.

P days: We use the predictive model WISDOM to determine the first fungicide application for prevention of early blight as well. 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. To date, 207 P-days have accumulated at the site. Once 300 P-days have accumulated, the first fungicide for early blight control should be applied. This usually occurs when rows are touching.