Purple Corn: purple corn symptoms (Image 1) are caused by the accumulation of a purple pigment in the corn leaves known as anthocyanin. Corn leaves produce sugars by photosynthesis and these sugars are typically metabolized to generate energy for further plant growth. However, when cool temperatures cause plant growth to slow or root development is restricted, these sugars tend to accumulate in the leaf and trigger anthocyanin pigment formation (e.g., purple leaf color). Purple corn can also occur from a genetic response to bright, sunny days and cool nights (Nielsen, 2000). In addition, hybrid genetics can play a role in whether or not a corn plant produces anthocyanin. This symptom often disappears with warmer temperatures and yield losses should be minimal to none.
Image 1: Purple corn leaf symptoms observed on V2 corn in Northern Indiana in 2021 caused by the build up of anthocyanin in the corn leaves due to cool temperatures.
Note: This symptom is often confused with phosphorus deficiency of corn. So, before you get the fertilizer spreader out once these symptoms occur, pay attention to your soil test levels and to the corn as temperatures become warmer and if these symptoms begin to disappear.
Yellow-Green Corn: cool temperatures and/or poor root/stand establishment can also cause corn to appear ugly yellow-green instead of that dark, beautiful green we are all looking for. Up until corn reaches the V3 growth stage (3 visibly collared leaves), the energy and nutrition of the seedlings are dependent on the kernel reserves. Once corn gets beyond the V3 growth stage, seedlings begin to transition to being dependent on the nodal root system. During this transition, when poor growing conditions occur this causes insufficient photosynthesis, slowed nodal root development, and poor plant nutrient uptake. Therefore, corn plants appear an ugly yellow-green. However, with more sunshine and higher temperatures, these symptoms are often resolved.
Rapid-Growth Syndrome: rapid growth syndrome often occurs when corn enters the V5 to V6 growth stage and is caused when the corn leaves fail to unfurl properly from the whorl. This often happens after drastic temperature changes, needed rainfall, root establishment, and an acceleration in plant growth. A common symptom is the whorl often becomes tightly wrapped and twisted on the plants. In addition, leaves that were trapped in the whorl will often emerge with a very noticeable bright yellow color (Image 2).
Image 2: Bright yellow leaves present in corn experiencing rapid growth syndrome in 2024.
Striped Corn: the presence of yellow and “striped” corn, specifically on the upper leaves of the plant, has been observed in multiple areas across Indiana in 2024 (Image 3). This symptom is largely caused by nutrient deficiencies, with the most common nutrient deficiency being sulfur.
Image 3: Upper leaf yellowing and striping occurring in V4 corn in Central Indiana following a rye cover crop in 2024.
Silver Corn: corn that has experienced cool, calm, and clear nights can cause radiational heat loss from corn leaves, thus causing minor leaf surface damage (Nielsen, 2021). This minor chilling injury can result in a silver or gray leaf surface often known as “silver leaf syndrome”.
Image 4: Silver corn leaf symptoms observed on V4 corn in central Indiana in 2023. (Photo Credit: Rachel Stevens)
White Corn: white or “bleached” corn leaves are often blamed on herbicide damage, specifically the pigment inhibitors herbicides (e.g., group 13 and 27). However, young corn that has been under environmental stress such as cool and cloudy weather, which can cause poor root development, can cause a white appearance (Hager and McGlamery, 1997). These symptoms have been observed previously on corn that has had significant root burn caused by a spring anhydrous application. Frost damage can also cause the bleaching of corn leaves. Furthermore, single, white corn plants within a field can be genetic mutants, although this is a rare occurrence.
Image 5: Corn at the V2 growth stage exhibiting symptoms of white corn leaves caused by stressful early-season conditions in 2021. (Photo Credit: Emma Spurgeon)
References:
Hager, A., and M. McGlamery. 1997. Causes of White Corn Plants. Univ. of Illinois Coop. Ext. Serv.
http://bulletin.ipm.illinois.edu/pastpest/articles/v9712g.html#:~:text=We%20have%20received%20several%20calls,glyphosate%20(Roundup%20or%20Touchdown).
Nielsen, R.L. 2000. Isn’t Corn Supposed to be Green? Corny News Network, Purdue Extension.
https://www.agry.purdue.edu/ext/corn/news/articles.00/Corn_color-0523.html.
Nielsen, R.L. 2010. Corn and the Ugly Duckling. Corny News Network, Purdue Extension. https://www.agry.purdue.edu/ext/corn/news/timeless/UglyDuckling.html
Nielsen, R.L. 2020. Assessing Frost/Cold Temperature Injury to Young Corn. Corny News Network, Purdue Extension. https://www.agry.purdue.edu/ext/corn/news/timeless/FrostedCorn.html.
Nielsen, R.L. 2021. “Silver Leaf” Syndrome in Corn. Corny News Network, Purdue Extension.
http://www.kingcorn.org/news/timeless/Silverleaf.html.
Quinn, D.J. 2021. Corn Growth Stages VE to V3…What’s Going On? Purdue Extension.
https://thekernel.info/corn-growth-stages-ve-to-v3whats-going-on/.
Silva, G. Purple Corn Syndrome: What Causes Purple Coloration of Corn? Michigan State University Ext.
https://www.canr.msu.edu/news/purple_corn_syndrome_what_causes_purple_coloration_of_corn.
