Growers are sending and bringing more physical samples to the University of Missouri Plant Diagnostic Clinic than in recent years. A high percentage of those samples deal with disease identification. Only a small number ask for identification or help on insect-related concerns.

Peng Tian says that’s what the most recent summary report of clinic activities indicates. He operates the lab, along with Pierce Taylor and Ethan Harmon.

In the most recent report, covering clinic activities from Jan. 1 to June 30, 39% of samples submitted concerned field crops, 34% were fruit-related, 19% on ornamentals, 5% on vegetables, 1% turf and 3% unclassified samples. Of field crop samples, 46% were wheat, 31% soybeans and 19% corn, with “other” at 13%.

Wheat sample numbers were much higher in 2024 than in 2022 because free wheat virus tests were offered, Tian notes.

“With collaboration with Mizzou Field Crop Pathology group, our clinic remains committed to identifying and managing these viruses to help farmers protect their wheat crops in the future,” Tian says.

Closer look

Here are trends picked up so far this year:

Wheat. Several wheat viruses were detected as positive in samples, Tian reports. They include wheat streak mosaic virus (WSMV), wheat spindle streak mosaic virus (WSSMV), soilborne wheat mosaic virus (SBWMV), barley yellow dwarf virus (BYDV), High Plains virus (HPV) and cereal yellow dwarf virus (CYDV). 

More than 85% of all wheat samples tested carried WSMV. However, numbers for SBWMV, WSSMV and BYDV positive samples were lower than in 2023. It’s notable, though, that HPV was detected from a sample collected in Montgomery County, Mo. This is the first time that this viral disease was reported in the state, Tian says.

Soybeans. Wet spring and early-summer conditions were reflected in soybean samples. Infections identified included multiple soilborne pathogens such as phytophthora crown and root rot. Pythium root rot was also identified in some samples, as was fusarium crown and root rot and rhizoctonia root and stem rot.

“We are closely looking for the emergence of several severe fungal root rot and stem rot diseases now,” Tian says. They include sudden death syndrome, or SDS, red crown rot and brown stem rot. Red crown rot was already confirmed in Indiana in 2024.

Corn. Diseases identified for corn included gray leaf spot, tar spot, and common and southern corn rust. Some samples were also identified with nutrient deficiencies, Tian reports. Some diseases in corn have picked up since June 30, when this report ended.

How to submit a plant sample

Submitting plant samples to the University of Missouri Plant Diagnostic Clinic and getting a confirmed diagnosis on plant problems can help you manage corn, soybeans and wheat better in the future.

Tian offers these easy steps for submitting samples: