In late May and early June, corn plants in some fields in Iowa have shown twisted whorls and buggy-whipping of corn leaves.

This condition is also known as rapid growth syndrome, accelerated growth syndrome, roping, wrapped whorls and onion leafing. It’s not unusual for this to occur when corn is growing rapidly, says Mark Licht, Iowa State University Extension cropping systems agronomist.

These symptoms of rapid growth syndrome usually occur in the V5 to V7 growth stage (fifth to seventh leaf corn) but can also show up as late as when corn forms the 12th leaf.

Most of the time these symptoms are due to rapid growth as plants benefit from warm temperatures, rainfall after being dry, or development of nodal roots. Due to genetic differences, some corn hybrids have a greater propensity for this occurrence than other hybrids, says Licht. Growth regulator and acetamide herbicides can also be the culprit.

Leaves unfurl after a few days
Typically, the wrapped whorls will unfurl in three to seven days. The outer leaves will have a rippled appearance and the inner leaves will be yellow to white in appearance. “As the plants grow and photosynthesis ramps up, those yellow leaves will green up rapidly,” notes Licht. “The affected plants will have minimal, if any, impact on grain yield. The take-home message is to be patient and let nature take its course.” 

Also, in some fields in Iowa this spring, there have been reports of herbicide carryover, stunted and uneven corn, and corn plants showing symptoms of sulfur deficiency. Rebecca Vittetoe, ISU Extension field agronomist in south-central and over into southeast Iowa, says phone calls she received during the week ending June 6 consisted of questions about herbicide carryover (ALS, PPO and HPPD herbicides), stunted and uneven corn growth, and sulfur deficiency.

ISU Extension field agronomist Meaghan Anderson covers east-central Iowa. Reporting on June 5, she noted: “Most corn in our area is just getting out of the ‘ugly duckling’ stage and reaching the V6 to V7 stage of growth, but some corn is still yellowed and uneven. Most of the phone calls I’ve received have been about stunted corn. The cause is soil compaction, variable soils, and variation in how quickly corn plants reach nitrogen. There are also some fields where herbicide carryover, ALS and PPO herbicides have caused these symptoms.”