man walking between rows of dried cornstalks
PUSH TEST: The push test may not be exciting, but it’s simple to do. Simply walk between two rows as Dave Nanda demonstrates here. Push on stalks. Ones that don’t snap back are likely infected with stalk rot.

Stalk rot varies by hybrid, affects standability

Corn Illustrated: Learn why you should do the push test on corn not yet harvested.

Maybe you’ve seen those commercials for a personal-identity theft protection company where someone only monitors a problem and doesn’t fix it. In one there is a bank robbery, and the customers and tellers hit the floor. A guy dressed as a security cop says, “There is a bank robbery.” Someone asks if he is going to do something. He replies, “Oh no, I am just a monitor, and I’m monitoring. There is a robbery.”

In some ways, the push test you can do in a cornfield shortly before harvest is much like the bank monitor. It can tell you if there is a problem. The problem you’re looking for is lack of stalk integrity, often caused by stalk rot. If you detect a problem, then it’s up to you to make decisions based on that information.

“The push test is simple and can be a helpful tool,” says Dave Nanda, independent crops consultant based in Indianapolis. “It doesn’t tell you what kind of stalk rot you have, or even for sure if your problem is stalk rot, but it can tell you if you need to look closer.”

The test is easy to administer, Nanda says. Simply count off 100 stalks. Then walk between the rows, pushing on one row and then the other. If five stalks go down per row, then there is 5% lodging potential. If 30 go down on each side, then there’s 30% potential.

Take action
The next step is to check out the stalks that went down to see if stalk rot is the problem. If the stalks are breaking or bending low near the ground and not snapping back, it’s likely stalk rot, Nanda says. You can examine the lower part of the stalk and check inside it for clues as to what type of stalk rot it might be. Black discoloration, specks on the outside and a dark pith on the inside in places may indicate anthracnose stalk rot.  

Next, decide if there is enough potential for lodging to mark the field for early harvest, or to be harvested next if it is late in the season. If only 5% of stalks don’t snap back, you likely can buy some time working elsewhere and waiting on field drydown, Nanda notes.

“However, when 25% to 30% don’t snap back and you confirm that it’s because stalk rot is present, you want to get that field harvested as soon as is practical,” he recommends. Otherwise, a late-season storm could cause considerable lodging. The percentage of stalks that fail the test will only go up as time passes.

Finally, take good notes on percentages you find in various hybrids. Take those differences into account when you are making final decisions on which hybrids to plant heavily, plant some of or cull next season, Nanda concludes.



TAGS: Crop Disease
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