Many growers couldn’t buy a rain during the first half of May, and then couldn’t escape threats of daily downpours during the month’s second half.  These periods of extreme weather have left some struggling to figure out the best next step in growing their crops in 2018. 

As one farmer confided with frustration May 30, “Bob, I am behind in all of my sprays, and I still have to plant 435 acres of cotton and peanuts.  How do I get out of this?”

The past two weeks of rain and the passage of Tropical Storm Alberto will very likely impact diseases and disease management options in at least four significant ways:

The rainy weather has had on impact on two diseases and, according to reports on social media, seems to have affected a third.  For peanut farmers, there is some good news.  Aspergillus crown rot, a disease that can punish a peanut crop during hot and dry conditions, becomes much less important, and often unimportant, in wet, cooler soils.  The rains have certainly slowed the development of Aspergillus crown rot. 

Unfortunately, soreshin seedling disease of cotton, caused by the fungus Rhizoctonia solani, has been widespread across some fields this season.  Unless growers take extra preventative measures to include use of additional seed treatments or in-furrow fungicides, there is nothing that can be done after closing the furrow.

On social media, a crop consultant from southern Georgia has reported bacterial blight on a young, susceptible cotton variety.  Without further testing I would not be able to say exactly how the disease got into the field.  However, recent periods of rain and 100% humidity have been perfect for infection to occur and for the disease to spread.  I am not surprised to learn that the disease was found by an observant consultant on a susceptible variety.  The final impact of the disease will be decided in large part by conditions throughout the rest of the season.

Extension agents and I are talking daily about critical management options for our growers now.  Here are two of the most important considerations. 

First, though southern corn rust has not been found, corn in many fields is risk for disease outbreak.  I have not issued a general recommendation to treat corn with a fungicide because we have not found rust.  Still, some growers will apply a fungicide anyway because of increased risk as a preventative spray can be very effective.  I expect fungicides like Tebuconazole and Tilt to provide about two weeks of protection.  I expect mixed products that include triazole, strobilurin, and/or SDHI fungicides to protect the crop for at least three weeks and perhaps longer.  Choice of fungicide is important; timeliness and coverage are perhaps even more important.

Some peanut farmers are late in applying the first fungicide to their crop and are at increased risk to leaf spot.  Growers who are behind in their fungicide program should get in the field as quickly as possible and consider using a systemic fungicide or mixing a systemic fungicide with their chlorothalonil for better control.  Examples of systemic fungicides or fungicide mixes include Priaxor, Alto, Domark and Absolute among others.  Timeliness is critical; systemic fungicides can help during periods of rainfall and delays in application.

Rain is not a bad thing.  As another grower messaged this week, “I’d rather be a little late planting into moisture than putting seed in dry dirt with no irrigation.  That is a recipe for bad seed stand and no residual chemical control.”  Excellent point; however the rain has also brought its own challenges.  I encourage growers to work with their local Extension offices to make best management decisions now and always.