If you wanted to cook up a recipe for unusual growth patterns in corn plants, you could start with the 2019 growing season as an example. When you wipe out most of the month of May for fieldwork because soils are too wet, and then throw in 5 inches of rain and 40-degree-F overnight temperatures in the middle of June, strange things can happen.
Some of those things are expected. The temperature drops to 40 degrees in mid-June produced enough chill injury on just-planted corn to prevent it from germinating. The unusual piece of that puzzle was that it happened in June, not April or even May.
Flooded areas can lead to diseases later, including smut. Corn smut isn’t difficult to find in some fields this year, although it likely won’t impact yield.
Flooding and saturated soils can also set up plants to be infected with crazy top, says Dave Nanda, director of genetics for Seed Genetics-Direct, Jeffersonville, Ohio. Seed Genetics-Direct sponsors Corn Watch ’19.
The fungal pathogen that causes crazy top survives in the soil and is present in most fields. If the soil is wet, especially if there is ponding, the fungus can invade the growing point of young corn. According to the Purdue University Corn and Soybean Field Guide, this can lead to excessive tillering and leaf development within the tassel. Sometimes leaf development happens in the ear area, although not as often. All or part of the tassel can be replaced with a somewhat unorganized mass of leaves.
That plant obviously won’t produce pollen. However, as the Purdue guide notes, it rarely causes yield impact because only plants here and there are affected.
Corn Watch example
Then there is the plant pictured here. It produced an ear without husks on top of the plant instead of a tassel. This plant was found in the Corn Watch ’19 field on the end rows.
Is it crazy top, or some other growth abnormality? “It doesn’t have the typical appearance of crazy top, but obviously something caused the plant to do something besides what it should have done,” Nanda explains.
The soil was saturated in early June, soon after emergence, with a ponded area near this plant. Also, being on an end row, it could have been injured by wheel traffic during herbicide application.
This is another example of what can go wrong when conditions are outside of what’s normal, Nanda says. And it also helps make his point that corn plants go to great lengths to try to reproduce.
“They want to make babies,” Nanda explains. “Note that there are some kernels on this out-of-place ear. This plant didn’t produce pollen, but the ear must have silked, and it picked up pollen from its neighbors.
“Also note that the plant was attempting to put out an ear shoot in the normal location, complete with silks. Even though it was beset with serious defects, it wasn’t giving up on trying to produce progeny. That’s one of the most amazing things about corn plants — they try as hard as possible to produce viable offspring.”
Corn plants don’t know that the kernels they produce won’t be replanted because they’re from a hybrid plant, Nanda says.