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.