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.

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