This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Red crown rot, a fungal disease of soybean, is not new to the Midwest. First reported in Illinois in 2018, the disease is now surging across the state and the region.
Boris Camiletti, a plant pathologist at the University of Illinois Urbana-Champaign, is leading the effort to understand and combat the scourge, along with the Crop Protection Network, the Illinois Soybean Association, the United Soybean Board and researchers in surrounding states. Red crown rot is caused by a fungus called Calonectria ilicicola (previously known as Cylindrocladium parasiticum). The fungus lives in soil, attacking roots.
"We know that it spreads with the soil, so any kind of soil movement or machinery that may have some soil attached, it's spreading that way," said Camiletti, an assistant professor and Illinois Extension specialist in the Department of Crop Sciences, part of the College of Agricultural, Consumer and Environmental Sciences at U. of I. Infection starts when tiny, hardened structures in the soil called microsclerotia germinate to sprout the vegetative body of the fungus, or hyphae. The threadlike hyphae then penetrate root cells and travel into the plant, producing toxins that eventually kill plant tissue.
Microsclerotia are extremely hardy and can persist in the soil for several years, Camiletti says. Nearby roots can stimulate them to germinate, and warm, wet conditions favor infection of young soybean roots. Red crown rot often becomes visible initially at the root crown, the location just under the soil where the roots meet the stem.
The crown and lower stem can take on a reddish tinge, accompanied by fungal structures, such as white patches or tiny brick-red spore-producing spheres known as perithecia. The disease may attack early in the life of the plant and persist or worsen throughout the season. A reddish stem may be visible during the vegetative stages (as early as V2) in soybean, but it's often not until the reproductive phases, typically between R3 and R5, that foliar symptoms can be observed.
Chlorosis, or yellowing, begins between veins, leading to necrosis, or leaf death. Severe infestations can decrease yield by 60%–70%. "This disease can produce foliar symptoms that are almost identical to more traditional diseases like sudden death syndrome and brown stem rot, or even damage from some fungicides like triazoles," Camiletti said.
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