A wet spring in Ohio. A season-long drought in the central and northern Corn Belt. Mother Nature provided all forms of weather for us this growing season. Unfortunately, those unfavorable conditions have led to a handful of late-season diseases that are starting to rear their inconvenient heads as harvest begins.
Tar Spot
Tar spot is a fungal disease that affects corn. It appears as small raised black spots on the leaves and husks of plants that sometimes can produce fisheye-like lesions. While it can often be confused with corn rust, one way to distinguish tar spot from other diseases is that the black spots will not rub off at the touch. That said, it’s always best to work with your local extension experts or a lab to diagnose the disease.
Unfortunately, tar spot can cause significant yield damage as infected plants can be prone to top leaf dieback, poor grain fill, compromised stalks and plant death. Tar spot this late in the season can lead to stalk rots and lodging, so it’s important to scout fields that may be impacted and perform the push/pinch test on your stalks to determine what fields need to come out first. Tar spot tends to favor wet, humid climates, so growers who experienced wetter-than-normal growing conditions and long periods of humidity may have fields susceptible to the disease. Tar spot is also able to overwinter in the ground, so while growers may not be able to tackle the disease this late in the season, they must plan for next year by selecting a hybrid with a better tolerance rating to tar spot or exploring relevant seed treatments with added fungicides. And a best practice with all diseases: Rotating the crop to a non-corn related crop can help keep tar spot at bay.
Stalk Rots
Stalk rots in corn are common at this time of year and can include different types of rot, such as gibberella, fusarium, diplodia and charcoal rots. This biggest indicator of stalk rot is brittle stalks that may be discolored as the fungus takes hold. As we discussed in last week’s article, growers really need to scout their fields to check for areas where stalks may be compromised so that they can prioritize those affected fields for harvest. And if the plant does snap, bend or feel soft to the touch, it’s good practice to split the stalk open to check the severity of the fungi feeding on the structural tissues and lignin.
Sudden Death Syndrome
As Stine Regional Sales Agronomist Grant Collier recently reported in Ohio’s Country Journal, sudden death syndrome (SDS), which is considered “one of the top two most destructive soybean diseases in the U.S.,” is present in areas of the country. Its presence is worrisome this year in his region in Ohio as a combination of moisture with cool weather has exacerbated the fungus. He notes soybean cyst nematode (SCN) is often found in conjunction with SDS and may be another culprit of SDS.
Symptoms of SDS include soft, rotten roots, discolored stems, fungus masses on the root, yellowing of leaves and leaf drop. While growers may not be able to do anything for SDS or SCN this season, selecting soybean varieties with both SDS and SCN resistance can slow the presence of the diseases in your fields next year. Stine has a number of varieties that are effective in controlling both diseases. Rotating to corn is also a good practice for minimizing risk, and as Grant notes, “minimizing tillage is essential to limiting the spread of SDS throughout your field, as well as SCN.”
To learn more about what diseases can be present in your fields this fall and how to get ahead of these diseases next year, contact your local Stine sales rep.