Robust root systems and targeted disease protection are two critical components of successful wheat and barley cultivation. Damaging soilborne and seedborne diseases like Pythium,Fusarium and Rhizoctonia can mutually reinforce each other to compromise root health and crop productivity, resulting in inconsistent and reduced yields.
Tough to detect above ground and often misdiagnosed as winter injuries or poor soil fertility, Pythium, Fusarium and Rhizoctonia are currently three of the most widespread soilborne diseases devastating cereal fields. These root pathogens linger in the soil, waiting to attack seeds after they are planted. Due to the pathogens’ concealed nature, Syngenta is on a quest to raise awareness of their presence in soils, as they can interact to envelop entire root systems.
Researchers at Syngenta are making strides toward providing cereal growers with more integrated solutions, including efforts to enhance disease protection with new seed treatment formulations, to help defend cereal seeds and seedlings against harmful, hidden diseases that nibble away at roots.
Wayne Pedersen, emeritus plant pathologist, University of Illinois, explained that “hidden diseases" are referred to as nibblers that feed on root systems, reducing the number of small, fibrous roots needed for adequate moisture and nutrient absorption.
“There may not be any visible symptoms from the nibblers [above ground], except a reduction in yield," Pedersen said.
Under favorable conditions, in wetter, cooler soils, these pathogens can induce a new round of infection in the next crop as they can survive in dead, infected roots for long periods of time. Soilborne pathogens infect the seed at or before germination, attacking the outside of the seed and the seed embryo. As a result, crops exhibit poor growth, and subsequently, growers experience reduced yield and revenue. The immediate threat, though, is to the seed and young seedling.
Some indications of active pathogens in cereal crops include infected or dead root tips, brown lesions, unmistakable bare patches in fields and light-weight, shriveled kernels – all of which ultimately coincide to foster yield loss. Resulting root lesions also provide potential points of entry for other pathogens. Additionally, seeds may germinate poorly or not at all, and seedlings may be slow to emerge, emerge unevenly or even die. And because diseases like Rhizoctonia destroy the absorptive capacity of the roots, infected crops face insufficient moisture and nutrient uptake, further reducing yields.
According to Tim Paulitz, Ph.D., research plant pathologist with USDA-Agricultural Research Service at Washington State University, it’s important to protect the roots early on.
“Apply some starter fertilizer in the furrow at the time of planting to help the seedling pick up nutrients, even if some of the roots are nibbled away by Rhizoctonia or Pythium," Paulitz noted. “Seed treatments are important in preventing Rhizoctonia and other soilborne pathogens in wheat. It’s a relatively small cost compared to other inputs."
Paulitz and his research associate, Kurt Schroeder, Ph.D., said when it comes to soilborne pathogens, whichever gets to the root first will have a foothold and perhaps outcompete another disease. Pythium, Fusarium and Rhizoctonia have different lifecycles and therefore different characteristics and geographical prevalence:
· “Fusarium infects the roots and eventually gets into the crown, or the bottom part of the stem near the soil. It manifests its symptoms later on in the growing season. This disease seems to be predisposed by drought stress.
· “Pythium infects germinating seeds and young seedlings very quickly and nibbles away at root tips. The disease is more prevalent in areas that have higher precipitation – over 18-20 inches of precipitation annually and is favored by wet, poorly drained soils. In most crops, one of the major symptoms is pre- and postemergence damping-off as well as reduced seedling vigor. If plants do emerge, they can become stunted later as the disease continues to nibble at the roots all season.