Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu
Location: Art and Keith Wicks Farm, Rt 9, Leipsic, Kent County
Greenrow: May 5
| Date |
DSV |
Total DSV |
Spray Interval Recommendation |
| 5/5 – 5/8 |
18 |
18 |
7-days |
| 5/5 – 5/12 |
3 |
21 |
7-days |
| 5/12 – 5/15 |
0 |
21 |
10-days |
| 5/15 – 5/20 |
11 |
32 |
5-days |
| 5/20 – 5/23 |
2 |
34 |
5-days |
The first late blight fungicide application is recommended once 18 Disease Severity Values (DSVs) accumulate from green row. Greenrow occurred on approximately May 5 at this location. Growers opting not to use the forecast system should put the first late blight fungicide application on when the plants are 6 inches tall, and repeat every 7 days. There are numerous fungicides now labeled for late blight control. See the 2013 Commercial Vegetable Production Recommendations-Delaware: http://extension.udel.edu/ag/vegetable-fruit-resources/commercial-vegetable-production-recommendations/
The threshold of 18 DSVs has been exceeded. Thirty-four (34) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 5. An additional two (2) DSVs have accumulated since the last report. Spraying as soon as possible with a protectant fungicide would be advised if not already on a spray program. Scout your fields regularly for symptoms. Any suspicious samples can be sent to the UD Plant Diagnostic Lab or dropped off at your local Extension office. Currently, Late Blight has only been detected in Florida.