Stem and petiole lesions are brown to black in color and are often covered with a whitish fuzz. When petioles are infected, the infection often spreads into leaflets, rapidly killing the affected leaflets. I wish there was a magic bullet, but there is none. Until we get a break on the weather pattern that continues to provide frequent wetting of the crop, cool nights with abundant dew and fog, control will be very difficult. One thing is apparent from scouting reports.
Infection is most obvious at field edges and areas that are difficult to spray.
For those having their fields sprayed by air, you must work with the pilot to insure that all the plants in a field are treated. In those areas of the field that are difficult to spray by air due to buildings, roads, powerlines, trees, etc., consider those areas your responsibility to treat by ground. Also, for those fields sprayed by ground, growers should sanitize tires and parts of the sprayer touching plants with a disinfectant to reduce the risk of carrying late blight inoculum from field to field. There are numerous treatments available for late blight management and most will do a reasonable job when coverage of all leaves and stems is achieved. Unfortunately total coverage is never achieved and repeated fungicide applications through the summer are needed to slow down disease spread and achieve as close to total control as possible.