Nebraska Farmer www.FarmProgress.com – April 2015 21 Crop Production By CURT ARENS T HERE is bad news when it comes to charcoal rot in Nebraska. You can’t beat it with a simple crop rotation because it loves a huge host of plants, including corn, soybeans, wheat, alfalfa, sorghum and dry beans, just to name a few. Seed and foliar fungicide treatments don’t work to reduce it. According to Tamara Jackson-Ziems, Nebraska Extension crop pathologist, there are no resistance packages available in modern hybrids. And, in 2014, CR, or dry weather wilt as it is sometimes known, was more widespread in soybeans in the state, with confirmations in Cass, Burt, Saunders and Keith counties. “Losses can range from very little loss to up to 50%, depending on the condition,” Jackson-Ziems says. The good news is that because it is a dry-weather fungus, it hits mostly nonirrigated fields. CR was an important disease in 2014 because of high temperatures and dry conditions in parts of the state. It also showed up in regions struck by wind and hail that already had stressed the crops. CR is caused by Macrophomina phaseolina, a soil and seedborne fungus that has over 500 hosts. It overwinters in crop debris and soil, surviving in hardened fungal structures that resemble charcoal dust. Food reserves in these structures allow it to remain dormant until conditions for growth are favorable. It can actually be present for many years without causing identifiable infection. “We saw many Nebraska soybean fields with symptoms in 2014,” says Tony Adesemoye Nebraska Extension disease management specialist. “The disease may not occur every time, except when conditions are conducive for the pathogen.” The United Soybean Board estimates that in 2011 soybean losses were 30 million bushels in 13 northern states and over a quarter-million in Nebraska. In soybeans, symptoms include browning or yellowing of leaves and stem, smaller-than-normal leaflets, blackcolored growths on the lower stem and root, and silver or gray lesions. It is easy to detect wilting in the infected portions of the field. In some cases, pods or ears may fill improperly, causing yield losses. Adesemoye’s research studies the biology of soilborne pathogens like CR and the interactions of those pathogens with organisms around the root that can be used as biocontrol agents in controlling pathogens in an integrated disease management system. “Our program examines the complex root ecosystems from a systems approach, and uses robust conven- Reduce plant stress Managing CR is a matter of reducing plant stress. Shorter-season varieties that canopy more quickly will keep soil temperatures lower during the hottest part of summer. Measures taken to retain moisture in the soil through less tillage or irrigation, as well as proper nutrient management, help produce healthier plants. Many pathogens can be controlled through crop rotation, but CR utilizes so many different crops as hosts that rotation will not help, says Jackson-Ziems. “Early diagnosis of CR does not lead to immediate rescue treatments in the growing season,” says Adesemoye. “Scientific information is emerging on the pathogen in the state, and the earlier the information on each infection and sampling in the field, the better the knowledge on the pathogen. Over time, we will have better management strategies.” tional and molecular tools,” Adesemoye says. “In 2014, we visited field locations suspected for CR, and we have recovered pathogens, which we are currently studying.” Producers who believe they have CR in the field should contact the UNL Plant and Pest Diagnostic Clinic at 402-472-2559, or call Adesemoye at 308-696-6708. often night when you call it a day. Because it’s We won’t tell you how to farm. We’ll just tell you we can help you farm the way you want to. W That you’ll harvest the most you can out of every minute of every day, in the field and across Th the farm. We’re as sure of that as the day is long. And you know how long that can be. th The high-definition TMX-2050™ display. See it at www.tmx2050.com. Th Beyond precision to decision. B ™ Android -based Ag Display © 2013–2015, Trimble Navigation Limited. All rights reserved. Trimble, the Globe & Triangle logo are trademarks of Trimble Navigation Limited, registered in the United States and in other countries. TMX-2050 is a trademark of Trimble Navigation Limited. Android is a trademark of Google Inc. All other trademarks are the property of their respective owners. UNL COURTESY PHOTO Charcoal rot is tough to beat