There's nothing like a week of dry weather to slow the progress of late blight. This has allowed growers to regain control of late blight and to establish a layer of protective fungicide on foliage and stems. Late blight is still active, however, as cool nights and dew have allowed some additional, although slow, spread of late blight. The undersides of leaf lesions are still ringed with a white fuzzy margin indicating that the fungus continues to produce new inoculum.
Some new lesions are present on unprotected plants indicating continued spread.
Intensive field scouting should continue so that hot spots are detected early and corrective action is taken. 50's are worrisome since these low temperatures favor the production of zoospores from sporangia distributed by rain and wind. It is not uncommon to find 8-10 zoospores produced from a single sporangium. Add to this the knowledge that under ideal conditions, up to 300,000 sporangia can be produced on a single leaf lesion and you get a rough idea of the reproductive capacity exhibited by the late blight fungus. In some fields, I've observed up to 8 individual fresh lesions on a single leaflet, a clear indication of zoospore release and infection.