Watch for Seedling Diseases in Early Planted Corn

Field conditions vary widely across the Midwest right now and may put early-planted corn at added risk for seedling diseases. In some areas cool soil temperatures and episodes of recent rainfall are especially favorable for some of the most common and damaging seedling diseases; in other areas, field conditions are quite dry. Numerous seedling diseases can occur and take advantage of any of these conditions. Be sure to monitor seedling emergence and stand establishment in the coming weeks so that if problems occur, they can be detected as early as possible.

Seedling diseases can be caused by any of several common soilborne organisms, such as Pythium, Fusarium, Rhizoctonia or plant parasitic nematodes. Seedling diseases are often difficult to diagnose because their symptoms are very similar. Sometimes diagnosis may be of limited value because management is the same for several seedling diseases. Microscopic examination and other laboratory analyses of the diseased seedlings often can identify the cause(s) of the problems. Seedling diseases can be confused with insect injury, herbicide damage, planting problems, or environmental stresses that often have similar symptoms. Some of the possible symptoms of seedling diseases are:

  • Rotted seed prior to germination
  • Rotted or discolored seedlings after germination prior to emergence
  • Post-emergence seedling damping off
  • Root or hypocotyl decay

At least 14 species of Pythium can cause seedling blight and root rot. These pathogens require excessive moisture because they produce motile swimming zoospores that infect plant roots. The pathogen overwinters in soil and infected plant debris by producing thick-walled oospores that can survive for several years in the absence of a suitable host or favorable weather conditions.

More than six Fusarium species can cause seedling diseases and root rots as well and several are common in Nebraska fields. Stressed plants due to weather extremes (temperature and moisture), herbicide damage, and physical injury are more prone to infection and disease caused by Fusarium species.

Rhizoctonia species also can cause seedling diseases, but tend to be more common in drier growing conditions. Rhizoctonia tends to cause reddish-brown lesions (Figure 4) that can girdle and rot off roots. Root and crown rot may be severe enough to cause seedling death.

Unfortunately, resistance is not available for seedling diseases in corn. Improved field drainage can help reduce the incidence and severity of some seedling diseases, as well as delaying planting until soil conditions are warmer and will promote rapid seed germination and emergence. The most common disease management is through the use of seed treatment fungicides.

Crop rotation can provide some reduction in disease, but some pathogens also may infect soybean and other crops.

Most seed corn is already treated with more than one seed treatment fungicide, often an insecticide, and, sometimes with a nematicide. These products provide protection against some of the pathogens that cause seedling diseases, but can be overwhelmed, such as during extended periods of inclement weather or under severe pathogen pressure.

Some fungicides also are labeled for application in-furrow at planting. Use of fungicides in-furrow at planting may provide some additional protection against these pathogens in fields with severe pathogen pressure and chronic seedling diseases, but more research needs to be conducted to better predict their potential benefits and economic return.

In Summary
Seed treatments will only provide protection during the first few weeks immediately after planting. You can minimize the likelihood of developing seedling diseases by planting high quality seed at appropriate planting depths and soil conditions to support rapid plant growth and emergence.

Source: Tamra Jackson-Ziems, University of Nebraska Extension

Recent News

Evaluating Alfalfa Stands Part 1 – Using the Hay Square Method

Were you expecting more from your alfalfa yields? Is it time to renovate, start over, or move on? Typically, evaluating stands occurs in the spring, but evaluating this fall will give you a better idea going forward and allow more time for future options. Evaluating stem/plant counts estimates the yield now. There are two options […]

Weather and the 2020 Illinois Corn and Soybean Crops

What a difference July rainfall makes. The U.S. Drought Map based on data through July 28 showed that only six percent of Illinois was rated as abnormally dry or with moderate drought, down from nearly 19 percent two weeks earlier. Above-normal rainfall over the past week in the southern half of Illinois will erase at […]

U.S., China to Discuss Phase One Trade Deal Later this Month

Lingling Wei and Bob Davis reported in today’s Wall Street Journal that, “The U.S. and China have agreed to high-level talks on Aug. 15 to assess Beijing’s compliance with the bilateral trade agreement signed early this year, according to people briefed on the matter. “The trade pact has emerged as one of the few remaining avenues for the two countries […]

Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now