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Row Crop Disease Update From Dr. Kemerait

Though we are still generally early in the season, there are a few things I want to make sure that you are aware of. (Dangling prepositions bother me, but not enough to fix them.)

  1. We have been allowed to continue our survey of kudzu old growth/regrowth in Georgia.  Last week we surveyed from Midville/Burke County in the east to Plains in the west and numerous locations in-between and south.  The first thing to not is that (no surprise) kudzu is rapidly breaking dormancy rapidly across the Coastal Plain.  Caleb was able to find it most anywhere he looked.  Most importantly, he only found “old growth” infected with rust and “new growth” infected with rust in a single kudzu patch- extreme southwest Georgia in the Donalsonville/Seminole County area.  We have been finding old-growth kudzu and infected new-growth kudzu throughout much of the winter, but now we only found soybean rust at the single location.  We will continue our survey efforts on a bi-weekly basis for now.
  2. Peanut seed quality issues and related issues with Aspergillus flavus, use of fungicide seed treatments, and in-furrow fungicides continue to be an issue and significant concern for growers.  Watch for Dr. Tim Brenneman’s article in “Peanut Pointers” Which Dr. Monfort will send out in the next few days for the most up-to-date information on seedling disease management in peanuts for 2020.
  3. PLANTING DATES:  Temperatures have been nearly “summer-like” recently and many growers are likely feeling the urge to put seed in the ground and to begin planting, perhaps making plants to plant earlier than usual.  Farmers, as a whole, are a “can do” and “git ‘er done” class of men and women and it can be hard for them to “wait”.  

The importance of picking a “best” or even a “better” planting date can have a tremendous impact on the threat of disease and nematodes to any crop.  Here are a few pointers.

  1.  Planting into warm soils supports rapid germination, rapid growth, and early-season vigor.  All of these things are helpful in the battle against seedling diseases and also to establish a root-system to minimize damage from nematodes.
  2. Planting in cooler, especially cooler and wetter soils, not only slows germination and development of the seedlings, but also gives the pathogens, mostly fungal pathogens in my row-crop world, and upper-hand in infecting and even killing seedlings.
  3. Planting earlier than normal because “the ground is warm enough and there is plenty of moisture” could easily back-fire on a grower.  Sure, it has been beautiful weather to plant for the past could of weeks.  But look what is coming tomorrow- cold rain and cooler temperatures, I wouldn’t want to have anything but corn in the ground now.
  4. Planting date can affect disease severity in ways other than “colder soils” or “warmer soils”.  For example, when using “Peanut Rx”, note that planting prior to 10 May, especially when peanuts are planted in April, increases risk to Tomato spotted wilt, as does planting later in May and into June.  Conversely, planting a bit later can reduce risk to white mold.  (See Peanut Rx)
  5. Planting dates are important to other crops as well.  For example, earlier-planted corn and soybeans are much less likely to be affected by southern corn rust and Asian soybean rust, than are later planted corn and soybeans.  Planting date can also have a significant impact on the likelihood of storms and wetter weather later in the season, particularly at harvest.  Whether we recognize it or not, some important reasons why we plant the varieties we plant and the dates when we do are to minimize boll rots in our cotton and late-season losses due to wet weather in our corn and soybean crops.
  6. The bottom line is that careful selection of an optimal planting date can have tremendous impact on the risk to diseases early in the season and throughout the season until harvest.  Sometimes, especially when a grower doesn’t have irrigation, you have to plant “into moisture”, whenever that might be.  However, recognizing the impact of planting date and the choice of planting dates, can make a world of difference.