The weather has been a double-edged sword of late throughout most of the mid-Atlantic region. The extremely hot weather with temperatures at or above 90 these past few days have been good for slowing disease development down. At those temperatures, its even too hot for pathogens to develop!
Unfortunately, the weather has also brought with it a lot of wind and rain these past few days and weeks. We all know what this leads to. Remember that bacteria need a wound or natural opening to enter a plant and cause an infection. The heavy winds and driving rains that beat up plants also help create the wounds that allow this to occur so its not unlikely to see an uptick in bacterial problems across a number of crops, such as in the case of bacterial leaf spot in tomato and pepper, after the weather we’ve had this past week.
Growers need to be proactive with copper applications and/or disinfestant applications prior to and/or after such events. Growers should also avoid working in fields when foliage is wet, if possible. This is extremely important if a bacterial problem is already present in the field!
The wet weather, along with the high humidity and prolonged leaf wetness also makes nice for many fungal pathogens, both leaf and soil-borne. Phytophthora blight in cucurbits, pepper, eggplant and tomato; Early blight in tomato; Alternaria and Anthracnose in cucurbits; and downy mildews just to name a few are favored by our current weather conditions, especially after temperatures cool down after todays weather front passes through the region.
During these conditions, all growers need to remain diligent and keep up with their protectant fungicide programs as long as field conditions allow and be proactive instead of reactive. After today, we get a few hours of dry weather before potential rains return on Thursday night into Friday.