Stunted Corn Observed in State
June 9, 1994 1(12):97
Chris Boerboom and Joe Lauer
Extension Weed Scientist and Agronomist
We have checked numerous fields in Columbia, Dane and Rock counties where stunted
corn has been reported. The corn in these fields was planted 1 to 2 inches deep
in late April and should be rapidly growing at this time. However, even though the
corn had uniformly emerged in these fields, many plants are stunted. The stunted
plants may only have 4 or 5 leaves and be 4 to 6 inches tall, often purplish. Leaves
tend to be more erect than normal. roots are partially stunted as well. Some of
the early roots have brown tips, but no other highly distinctive symptoms are evident.
Stunted root systems also become more susceptible to infection by root pathogens,
which may increase the severity of a problem. A row may have several stunted plants
together before normal vigorous plants are seen. Stunted plants are in scattered
patches to a couple of acres in size.
Although "classical" herbicide injury symptoms are not seen in these fields,
most of the fields that we have looked at have been treated preemergence or at spike
with Banvel, Clarity, or Marksman. All of these products contain dicamba. Dicamba
injury is often associated with wrapped or "buggy whipped" leaves, but
stunted corn from preemergence applications of dicamba has been noted at the Hancock
trials in the past. Typically, dicamba applied preemergence, applied to sandy or
low organic matter soils, and applied to shallow planted corn increases the chance
for dicamba injury compared to post emergence applications on fine textured soils
and to deeper planted corn.
Another field with patches of stunted corn was seen following preplant incorporated
Broadstrike. Broadstrike symptoms can include stunted roots with many branch roots,
which look like a "bottle-brush." This field did not have these distinctive
root symptoms. Weed scientists at Iowa State University have received several reports
of corn with poor root development in fields treated with Broadstrike or in corn
fields following soybeans treated with Pursuit. Both of these herbicides are ALS
inhibitors and cause similar injury.
In all of these cases, the amount of rain received over the next week will probably
determine how much the stunted corn plants will recover. Most plants have some healthy
roots that should keep growing with another good rain.