We all know the dark big spots of the Common Rust. It is a fungus that produces spore-filled pustules on corn leaves. The grain and seed industry offers many different corn hybrids that are fairly resistant to this decease. But now reports emerged about Southern Rust being spotted as far north as Illinois, Kansas, Kentucky, and Nebraska. This fungus is a whole different beast.
Southern Rust shows as small reddish orange pustules on the top of corn leaves, and can cause up to 45% yield loss. Especially when the corn gets infected during the grain fill period, and the corn loses leaf area, is the time the yield gets impacted.
Both the common rust and the southern rust produce pustules with up to 5,000 spores per pustules. Per leaf there might be several hundred little pustules. You can do the math, it does not take much, and there are a million spores coming from one corn leaf. Rust fungi only need about six hours in warm weather of 70 to 85 F with a relative humidity of at least 95% or leaf wetness for the spores to germinate, and to infect the plants. The spores travel through the air, and will infect other parts of the field quickly.
Unlike Common Rust, which many hybrids are immune to, there is no resistance engineered yet for southern rust. And unlike with common rust that can be effectively sprayed with a variety of well working fungicides, there is no effective spray on the market yet for southern rust.
The damage caused by Southern Rust depends on the stage the corn is at. Every field has to be evaluated individually. Tamra Jackson, a plant pathologist at the University of Nebraska, recommends that if the corn is near or getting ready to dent to just ignore the southern rust. But if your corn is still in milk, and if you have a pretty susceptible corn hybrid, then, according to Jackson, with the right weather, the southern rust could do a lot of damage. So it is important to scout your fields regularly, and carefully for the next few weeks.
Of course we always hope for the best, and we always hope that your crop turns out to be the best ever. To help you get an accurate weight of your corn, and an accurate moisture content reading of your crop, please contact us via e-mail or call us toll free at 866-668-4855.