Every Field Deserves the 'Push' Test

It's worth trip to each field to check on stalk rot.

Published on: Oct 13, 2008

Two of the Corn Illustrated plots were planted on the same day, with the same two hybrids, just two miles apart. Yet stalk rot is very prevalent in one of the plots, but not the other. In fact, the second plot was still green when most corn in the first field was already brown and looking 'fall-like.' What does this mean to you?

"Check each field out for stalk rot to see if you need to be harvesting it sooner than others," advises Dave Nanda, Corn Illustrated consultant. Nanda is also a long-time plant breeder, and currently president of Bird Hybrids, LLC, a small, independent seed company based in Tiffin, Ohio.

Even if it means driving to the back forty, it could be worth the effort, Nanda says. Each field has its own set of micro-climate conditions, including weather and other factors. If your fields are spread out over several miles, it's quite possible rainfall amounts and timing of rainfall varies. Lack of rainfall leads to stress, and stress is one of the factors setting corn plants up for stalk rots.

Another main factor in many areas this year is a late-season nitrogen shortage. On fields where N was already applied, either last fall or in some cases even earlier this spring, before June deluges hit, N losses have turned out to be significant. Nanda saw signs of corn running out of N in many locations across the Midwest in August and September. Nowhere was it more graphic than at the Corn Illustrated plot- the first plot referred to in this story. When plants run short of N, so severely that leaves above the ear leaf fire, not only is yield likely cut, but the plants are stressed, and more susceptible to stalk rot. It's a double whammy- lower yields and likely more stalk lodging unless harvest occurs as soon as possible.

One big difference between the two Corn Illustrated plot fields referred to here was the difference in N rates. One field received about 170 total pounds of N, the later one, the one still green in September, received closer to 250 pounds of N per acre. It is the high yield plot, and the idea was to make sure that N wasn't a limiting factor for yield. That could have been a real probability as this year turned out.

So once you're in the field, how do you do the 'push' test? It's simple, Nanda says. Simply walk into the field to representative locations, preferably picked at random, then walk down the row, pushing over on stalks. Those that spring back are still healthy. Those that bend or stay over obviously have already lost stalk integrity.

To see if stalk rot is the culprit, pull off stalks and cut the stalk down the middle lengthwise from the base of the stalk near the ground, up through the next few nodes. Brown pith tissue would indicate stalk rot. Also, if pith tissue is still white, but nodes are brown, maybe even brown and mushy, stalk rot invasion has begun. The nodes would be showing signs of stalk rot infection.

To turn the check into an actual count, inspect a hundred stalks down the row. The number that didn't come back becomes the percentage of stalks infested with stalk rot. The best advice is to repeat this simple test at various locations within the field before making a decision on when any particular field should be harvested next.