Nancy Gregory, Plant Diagnostician; ngregory@udel.edu
Average monthly temperatures in Fahrenheit at Georgetown, DE, Research and Education Center. 2003-13
| 2012-13 | 2011-2012 | 2010-2011 | 2009-2010 | 2008-2009 | 2007-2008 | 2006-2007 | 2005-2006 | 2004-2005 | 2003-2004 | |
| December | 40.1 | 43.2 | 31.3 | 37.9 | 41.8 | 39.7 | 43.5 | 36.2 | 38.9 | 38.6 |
| January | 37.4 | 39.5 | 31.0 | 32.7 | 31.0 | 36.8 | 39.7 | 43.0 | 34.9 | 29.5 |
| February | 35.5 | 40.4 | 39.6 | 31.1 | 39.2 | 39.9 | 30.1 | 37.4 | 36.7 | 35.2 |
| INDEX | 113 | 123.1 | 101.9 | 101 .7 | 112.0 | 116.4 | 113.3 | 116.6 | 110.5 | 103.3 |
Average monthly temperatures in Fahrenheit at Newark, DE Experiment Station. 2003-13
| 2012-13 | 2011-2012 | 2010-2011 | 2009-2010 | 2008-2009 | 2007-2008 | 2006-2007 | 2005-2006 | 2004-2005 | 2003-2004 | |
| December | 37.2 | 41.3 | 30.8 | 34.9 | 37.1 | 37.5 | 42.5 | 34.0 | 35.5 | 34.0 |
| January | 34.9 | 37.0 | 28.7 | 31.6 | 28.0 | 35.5 | 37.3 | 39.5 | 31.0 | 26.4 |
| February | 33.9 | 39.5 | 35.2 | 31.0 | 35.8 | 36.5 | 27.8 | 34.5 | 34.2 | 33.1 |
| INDEX | 106 | 117.8 | 94.7 | 97. 5 | 100.9 | 109.5 | 107.6 | 108.0 | 100.7 | 93.5 |
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 2013
|
Average Temperature (Dec, Jan, Feb) |
|||
| Location | Index & Rating |
2012-13 |
2011-12 |
| Georgetown: | 113=Severe |
37.7 |
41.0 |
| Dover: | 109=Severe |
36.4 |
40.3 |
| Newark: | 106=Severe |
35.3 |
39.7 |
Control Strategies: Resistant varieties are available. For processing and fresh market growers 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 2013 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/
See http://extension.udel.edu/ag/2013/03/13/winter-temperature-index-for-predicting-stewarts-wilt-in-delaware-sweet-corn-2013/ for pictures of Stewart’s wilt.