A season in decline — diagnosing a failing crop

Glenn Carter of Armstrong County knew something was wrong.

In 2023, his corn began browning seemingly overnight despite his irrigation efforts. A seasoned farmer of corn, cotton, sorghum, wheat, hay grazer and alfalfa, Carter had seen drought, pests and disease. But this felt different. He didn’t know why his field was turning brown.

“It looked like my crop was burning up, but I was watering,” Carter said. “I didn’t know who to call at first, but I’ve reached out to the Texas A&M AgriLife Extension Service specialists in Amarillo on multiple issues in the past. They’ve always been there.”

For Carter, AgriLife Extension has been more than just a source of information. It has been a trusted partner. “Whether it’s a meeting or just a phone call, someone always makes the time,” he said. “I knew they would help me find answers.”

A new corn disease in the High Plains

Carter’s call connected him with Ken Obasa, Ph.D., AgriLife Extension plant pathologist, director of the Texas High Plains Plant Disease Diagnostic Laboratory and assistant professor in the Department of Plant Pathology and Microbiology, Amarillo.

Obasa had a strong suspicion: Carter’s field was showing characteristic signs of a new disease, a late-season decline in corn, which he’d identified just a few years earlier. The symptoms were telling: browning plants and distinctive foliar necrosis, starting from the leaf tips and progressing backward.

In 2020, Obasa first identified late-season decline in corn during a fungicide research trial at the Texas A&M AgriLife James Bush Farm at Bushland. At the time, healthy corn plants suddenly exhibited symptoms similar to drought stress. They died within a week, resulting in nearly complete yield loss. Obasa quickly confirmed identical symptoms in multiple nearby fields, including three additional research plots in Bushland and a corn field in Ochiltree County.

After seeing the pattern of symptoms, Obasa identified and validated the causative bacterial pathogen, Pantoea ananatis, using the advanced diagnostic tools in his lab at the Texas A&M AgriLife Research and Extension Center in Amarillo. Depending on prevailing factors, the resulting crop loss can range from minimal to more than 90%.

“I’m sure it had been showing up in fields before,” Obasa said. “But in 2020, that was the first time I recognized it for what it was. Previously, I thought these conditions were caused by drought stress.”

With the diagnosis comes informed decisions

Already familiar with the symptoms described by Carter, Obasa visited his field and confirmed the problem was late-season decline disease. Carter said Obasa’s diagnosis allowed him to make critical adjustments to determine how long he could continue to grow his crop without wasting more inputs.

“What Dr. Obasa did helped us minimize our losses,” he said. “I stopped trying to take the corn to grain, which saved at least one watering and allowed me to use less fertilizer. We salvaged what we could by chopping it instead.”

A year later, Carter found himself in a similar situation — this time while helping his father at their family home across the Texas state line near San Jon, New Mexico. His father was growing a special crop of food-grade red corn under contract. It was the same situation all over again. The corn looked healthy one week, then declined fast with similar drought-like symptoms.

“Once again, I called Dr. Obasa,” Carter said. “He came out and saw the disease spread through almost the entire field. But because it was food-grade corn under contract, it needed to be taken to harvest. His advice helped us get what we could and meet the contract.”

A growing threat and a growing response for corn producers

Carter is far from alone. Obasa said the disease has appeared in Panhandle corn fields every year since 2020, regardless of the environmental conditions.

Currently, there is no known treatment or resistant corn hybrid; therefore, early detection is key so producers can make effective decisions to mitigate losses.

“Once symptoms appear, a producer must decide quickly, either moving it on to grain or cutting it for silage,” Obasa said. “But if you wait too long, everything will dry out, and it won’t even be valuable for silage.”

He said producers will first see symptoms as light green, elongated lesions with nonwavy margins on infected leaves. Plants infected early in the season become stunted and have delayed tasseling.

Disease spread beyond corn

Unfortunately, corn isn’t the only crop affected by this disease.

In 2023, foliar symptoms consistent with those of late-season decline were observed on leaves of sorghum plants in six fields across Potter, Hutchinson and Moore counties by Obasa and AgriLife Extension county agents. Additionally, U.S. Department of Agriculture officials have also reached out to Obasa after seeing a similar disease in rice and signs in wheat as well.

Obasa and a growing team of researchers are now part of a multi-university working group, including USDA-Agricultural Research Service scientists, to monitor and investigate the disease caused by this bacteria in corn, sorghum, rice and other affected crops. In recognition of the emerging threat posed by Pantoea bacterial pathogens to agricultural crops, an international conference on Pantoea is scheduled for mid-2025.

“We’re still learning about the disease and the causative pathogen, even as it continues to spread,” Obasa said. “We hope to find greater and more effective solutions to help more growers like Glenn Carter and his father.”

For Carter, the experience has only deepened his trust in AgriLife Extension.