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 |
| 5/23 – 5/27 |
5 |
39 |
5-days |
| 5/27 – 5-30 |
0 |
39 |
10-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-nine (39) DSVs have accumulated so far for any potatoes that established green row (approximately 50% emergence) prior to and since May 5. An additional five (5) 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.