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Cafe. We're getting calls and samples from growers in southern Indiana regarding suspected herbicide injury to newly emerged corn. The plants are twisted and leaves are improperly unfurling from the whorl (i.e. "shepherd's crook", "laddering"). In most cases a chloroacetamide (acetanilide) such as Dual, Frontier, Harness, Lasso, Micro-Tech, Partner, Surpass or TopNotch had been applied either preplant or shortly after planting. These herbicides may cause symptoms as described above with injury more often associated with cool and wet soils. Crusting from hard rains may also contribute to unfurling below the soil line.
To complicate things more, 2,4-D was used as a tank mix partner, in most cases, to burndown large broadleaves at or near planting. Corn injury from 2,4-D include both shoot and root symptoms. The shoots may be tightly rolled or buggy-whipped and plants may lean. The seedling roots may display clustering of short, stubby lateral roots around the seed or primary seed root. Injury from 2,4-D can occur, especially if the amine salt form was used with a good soaking rain following soon after application. Amine forms (e.g. Weedar 64, Formula 40) are more water soluble than the ester forms and, therefore, can move with the rain water into the seed furrow. Ester forms (e.g. Weedone LV4, Weedone 638) are less soluble, but may still cause injury if the corn is shallow planted, soil is sandy, or the seed slot was not properly closed allowing the chance for the 2,4-D to reach the germinating seed.
The 2,4-D labels that I have for preemergence use (both amine and ester labels) state that the 2,4-D should be applied 7 to 14 days before planting and 3 to 5 days after planting but before the corn emerges. Thus, applications made at or just prior to planting or after the corn is spiking would be considered an off-label treatment.
If the corn plant is so tightly rolled that you could dip the tip into ink and write a disaster claim to your insurance agent, then it's likely that the plant will not recover. However, most of the plants we have seen this spring, as well in past years, can "break" out of the strapping and produce a normal plant, IF weather conditions are conducive to good growth (e.g. sunshine and heat).
Be sure to check the root system, too. If it appears healthy, then the plants will generally recover or grow out of the shoot injury. Injured roots certainly will not help a plant with a twisted shoot, and these plants may indeed give up the fight. So if you have a plant with a twisted shoot but a healthy root system, leave it. It may be less of a risk to leave these plants than to replant at this late date.
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Cafe.
The Corn Growers Guidebook , a WWW
resource for corn management systems in Indiana and the eastern CornBelt.
Purdue University Agronomy Extension
WWW Home Page.
Purdue Agronomy On-Line! ,
Purdue's Agronomy Department WWW Home Page.