Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Disease Severity Value (DSV) Accumulation as of July 8, 2009 is as follows:
Location: Shadybrook Farms, Little Creek, DE in Kent County.
Greenrow: May 1
| LATE BLIGHT | EARLY BLIGHT | |||
| Date | Daily DSV | Total DSV | Spray Recs | Accumulated P-days* |
| 6/20-6/21 | 1 | 111 | 5-day interval | 434 |
| 6/22-6/23 | 0 | 111 | 7-day interval | 462 |
| 6/24 | 1 | 112 | 7-day interval | 470 |
| 6/25-6/28 | 0 | 112 | 10-day interval | 495 |
| 6/29 | 0 | 112 | 10-day interval | 503 |
| 6/30 | 0 | 112 | 10-day interval | 511 |
| 7/1 | 2 | 114 | 10-day interval | 519 |
| 7/2 | 1 | 115 | 10-day interval | 528 |
| 7/3-7/5 | 0 | 115 | 10-day interval | 555 |
| 7/6-7/8 | 0 | 115 | 10-day interval | 581 |
There have been no new late blight reports on potato or tomato from DE since Monday, when a small area under power lines that had not been covered well was discovered with late blight east of Dover. The recent clear days and low humidity are not favorable for new infections. There is no reason for concern if your fields were sprayed several times with a late blight fungicide during the last several weeks. Be sure to keep scouting, especially in those areas where fungicide coverage might not be the best or next to woods lines, places where the dew lingers in the morning, low areas, etc. The weather now is not very favorable for late blight but continue with preventative fungicides if crop development requires more growing time. It looks like we are going to get a break in the weather in that it will not be favorable for late blight again for the next few days but will continue to be favorable for early blight.
Ground application of fungicides would be recommended for areas or fields that have obstructions (under power lines, next to buildings, fence rows, etc.) that prevent effective aerial applications of fungicides since there is still late blight in the area.