Posts Tagged ‘Stewart’s wilt’

Risk of Stewart’s Wilt in Sweet Corn is High in 2012

Thursday, March 29th, 2012

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

The Stewart’s wilt prediction for 2012, as you can imagine with a very mild winter, is severe for all three counties in Delaware. We have not had such a mild December, January and February since the winter of 2001-2002 when the Index was 123.1 for Georgetown and 123.0 for Newark. The following table tells it all.

Winter Temperature Index For Predicting Stewart’s Wilt in Delaware Sweet Corn: 2002-2012

Average monthly temperatures in °F at Georgetown, DE, REC: 2002-2012

  2011-2012 2010-2011 2009-2010 2008-2009 2007-2008 2006-2007 2005-2006 2004-2005 2003-2004 2002-2003
December 43.2 31.3 37.9 41.8 39.7 43.5 36.2 38.9 38.6 36.7
January 39.5 31.0 32.7 31.0 36.8 39.7 43.0 34.9 29.5 28.9
February 40.4 39.6 31.1 39.2 39.9 30.1 37.4 36.7 35.2 33.8
INDEX 123.1 101.9 101 .7 112.0 116.4 113.3 116.6 110.5 103.3 99.4

 

Average monthly temperatures in °F at Newark, DE, Experiment Station: 2002-2012.

  2011-2012 2010-2011 2009-2010 2008-2009 2007-2008 2006-2007 2005-2006 2004-2005 2003-2004 2002-2003
December 41.3 30.8 34.9 37.1 37.5 42.5 34.0 35.5 34.0 33.5
January 37.0 28.7 31.6 28.0 35.5 37.3 39.5 31.0 26.4 27.1
February 39.5 35.2 31.0 35.8 36.5 27.8 34.5 34.2 33.1 29.5
INDEX 117.8 94.7 97. 5 100.9 109.5 107.6 108.0 100.7 93.5 90.1

Severity Index: < 90, usually absent; 90-100, intermediate; >100, usually severe.

The index is used to predict overwintering flea beetle populations that vector the Stewart’s wilt bacterium, Pantoea stewartii.

Prediction for 2012

      Average Temperature for Dec, Jan & Feb
Location Prediction   2011-2012 2010-2011
Georgetown 123.1=Severe   41.0°F 34.0°F
Dover 121.0=Severe   40.3°F 32.5°F
Newark 117.8=Severe   39.3°F 31.6°F

 

Control Strategies
For processing and fresh market growers the high risk of Swetart’s wilt means that if you are planting susceptible or moderately susceptible hybrids, flea beetle control is very important. A number of strategies are available including seed treatments, granular insecticides at planting and/or foliar applied insecticides after emergence. For foliar applied insecticides treat susceptible cultivars at spike stage when 5% of the plants are infested. See the 2012 Delaware Commercial Vegetable Production Recommendations for control suggestions.

Note: Weather records from University of Delaware Carvel REC, Georgetown, DE, DE State Fire School, Dover, DE and University of Delaware Ag Experiment Station Farm, Newark, DE. Data records found online at http://www.deos.udel.edu/

Winter Temperature Index for Predicting Stewart’s Wilt in Delaware Sweet Corn 2001-2011

Friday, April 1st, 2011

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

Severity Index: < 90, usually absent; 90-100, intermediate; >100, usually severe.

The index is used to predict overwintering flea beetle populations that vector the Stewart’s wilt bacterium, Pantoea stewartii.

Prediction for 2011

Georgetown: 101.9 = Severe         Avg. monthly temp (Dec, Jan, Feb) = 34.0°F

Dover: 97.5 = Intermediate  Avg. monthly temp = 32.5°F

Newark: 94.7 = Intermediate  Avg. monthly temp = 31.6°F

Average monthly temperatures in oF at Georgetown, DE. REC. 2001-2011

2010-11 2009-10 2008- 09 2007-08 2006-07 2005-06 2004-05 2003- 04 2002-03 2001-02
December 31.3 37.9 41.8 39.7 43.5 36.2 38.9 38.6 36.7 43.2
January 31.0 32.7 31.0 36.8 39.7 43.0 34.9 29.5 28.9 40.0
February 39.6 31.1 39.2 39.9 30.1 37.4 36.7 35.2 33.8 39.9
INDEX 101.9 101 .7 112.0 116.4 113.3 116.6 110.5 103.3 99.4 123.1

Average monthly temperatures in oF at Newark, DE Experiment Station 2001-2011

2010-11 2009-10 2008- 09 2007-08 2006-07 2005-06 2004-05 2003- 04 2002-03 2001-02
December 30.8 34.9 37.1 37.5 42.5 34.0 35.5 34.0 33.5 43.3
January 28.7 31.6 28.0 35.5 37.3 39.5 31.0 26.4 27.1 39.6
February 35.2 31.0 35.8 36.5 27.8 34.5 34.2 33.1 29.5 40.1
INDEX 94.7 97. 5 100.9 109.5 107.6 108.0 100.7 93.5 90.1 123.0

Control Strategies

For processing and fresh market growers this means that if you are planting susceptible or moderately susceptible hybrids that flea beetle control is very important. A number of strategies are available including seed treatments, granular insecticides at planting and/or foliar applied insecticides after emergence. For foliar applied insecticides treat susceptible cultivars at spike stage when 5% of the plants are infested. See the 2011 Delaware Commercial Vegetable Production Recommendations for control suggestions.

Note: Weather records from University of Delaware Carvel REC, Georgetown, DE, DE State Fire School, Dover, DE and University of Delaware Ag Experiment Station Farm, Newark, DE. Data records found online at http://www.deos.udel.edu/.

Winter Temperature Index for Predicting Stewart’s Wilt in Delaware Sweet Corn 2000-2010

Thursday, March 25th, 2010

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

Prediction for 2010
Georgetown: 101.7 = Severe – Avg. monthly temp (Dec, Jan, Feb) = 33.9 °F
Newark: 97.5 = Intermediate – Avg. monthly temp = 32.5 °F

Control Strategies
For processing and fresh market growers this means that if you are planting susceptible or moderately susceptible hybrids that flea beetle control is very important. A number of strategies are available including seed treatments, granular insecticides at planting and/or foliar applied insecticides after emergence. For foliar applied insecticides treat susceptible cultivars at spike stage when 5% of the plants are infested. See the 2010 Delaware Commercial Vegetable Production Recommendations for control suggestions.

Average monthly temperatures in °F at Georgetown, DE. REC. 2000-2010

2009-2010 2008-2009 2007-2008 2006-2007 2005-2006 2004-2005 2003-2004 2002-2003 2001-2002 2000-2001
December 37.9 41.8 39.7 43.5 36.2 38.9 38.6 36.7 43.2 31.2
January 32.7 31.0 36.8 39.7 43.0 34.9 29.5 28.9 40.0 33.8
February 31.1 39.2 39.9 30.1 37.4 36.7 35.2 33.8 39.9 38.8
INDEX 101 .7 112.0 116.4 113.3 116.6 110.5 103.3 99.4 123.1 103.8

Average monthly temperatures in °F at Newark, DE Experiment Station. 2000-2010.

2009-2010 2008-2009 2007-2008 2006-2007 2005-2006 2004-2005 2003-2004 2002-2003 2001-2002 2000-2001
December 34.9 37.1 37.5 42.5 34.0 35.5 34.0 33.5 43.3 31.1
January 31.6 28.0 35.5 37.3 39.5 31.0 26.4 27.1 39.6 31.5
February 31.0 35.8 36.5 27.8 34.5 34.2 33.1 29.5 40.1 38.4
INDEX 97. 5 100.9 109.5 107.6 108.0 100.7 93.5 90.1 123.0 101.0

Severity Index: < 90, usually absent; 90-100, intermediate; >100, usually severe.

The index is used to predict overwintering flea beetle populations that vector the Stewart’s wilt bacterium, Pantoea stewartii.

Note: Weather records from University of Delaware Carvel REC, Georgetown, DE and University of Delaware Ag Experiment Station Farm, Newark, DE. Data records found online at http://www.deos.udel.edu/

Winter Temperature Index for Predicting Stewart’s Wilt in Delaware Sweet Corn, 1998-2008

Friday, March 28th, 2008

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

Prediction for 2008
Newark:        109.5 = Severe- average monthly temp (Dec, Jan, Feb) was 36.5°F Georgetown:  116.4 = Severe – average monthly temp (Dec, Jan, Feb) was 38.8°F

For processing and fresh market growers this means that if you are planting susceptible or moderately susceptible hybrids, flea beetle control is very important. A number of strategies are available including seed treatments, granular insecticides at planting and/or foliar applied insecticides after emergence.

Average monthly temperatures in °F at Georgetown, DE REC 1998-2008

  2007-08 2006-07 2005-06 2004-05 2003-04 2002-03 2001-02 2000-01 1999-00 1998-99
December 39.7 43.5 36.2 38.9 38.6 36.7 43.2 31.2 40.3 41.3
January 36.8 39.7 43.0 34.9 29.5 28.9 40.0 33.8 33.9 39.5
February 39.9 30.1 37.4 36.7 35.2 33.8 39.9 38.8 39.7 38.7
INDEX 116.4 113.3 116.6 110.5 103.3 99.4 123.1 103.8 113.9 119.5

Average monthly temperatures in °F at Newark, DE Experiment Station 1998-2008

  2007-08 2006-07 2005-06 2004-05 2003- 04 2002-03 2001-02 2000-01 1999-00 1998-99
December 37.5 42.5 34.0 35.5 34.0 33.5 43.3 31.1 39.1 41.0
January 35.5 37.3 39.5 31.0 26.4 27.1 39.6 31.5 32.6 34.8
February 36.5 27.8 34.5 34.2 33.1 29.5 40.1 38.4 37.8 38.0
INDEX 109.5 107.6 108.0 100.7 93.5 90.1 123.0 101.0 109.5 113.8

Severity Index: < 90, usually absent; 90-100, intermediate; >100, usually severe. The index is used to predict overwintering flea beetle populations that vector the Stewart’s wilt bacterium, Pantoea stewartii.

Note: Weather records from University of Delaware Carvel REC, Georgetown, DE and University of Delaware Ag Experiment Station Farm, Newark, DE. Thanks for the data go to Dean Dey at Georgetown and Scott Hopkins, Farm Manger, UD Ag Experiment Station, Newark.