University of Missouri Plant Diagnostic Clinic 2024 Annual Report for Field Crops

By Ethan Harmon

In 2024, the MU Plant Diagnostic Clinic (MU-PDC) has received 813 physical samples and 337 digital samples (Figure 1, 2, 3). Among all the samples, 759 samples are submitted for plant disease diagnosis, while 28 samples are for insect identification services and 12 samples for weed identification (Figure 1). The months in late summer and early fall are the ones with the greatest number of sample submission, accounting for 68% of the samples of the entire year (Figure 2). The number of samples for research project has reduced from 400 to 112 in 2024, indicating that the lab received more service samples in 2024 compared to 2023.

Figure 1 Number of samples by service type.

Figure 2 Comparison of physical sample number by month in 2021-2024.

Figure 3 Comparison of digital sample number by month in 2022-2024.

The number of digital samples continues to increase in 2024, showing the strong need from the public for digital diagnostic services (Figure 3). To address this issue, MU-PDC is implementing digital sample submission system to assist in smooth and timely service in 2025.

In terms of the sample source, MU-PDC serves a broad range of clients across the state as well as out of the state. Based on the type of clients, there are four major groups (Table 1). In total, 48 out-of-state samples were received by the clinic in 2024, contrasting 765 in-state samples submitted from 88 counties (Figure 4).

Table 1 Sample sources of 2024 submission. Nonextension noncommercial clients include homeowners, home gardeners, research groups and scientists; Extension noncommercial clients include university extension offices, extension specialists and agents, and regulatory agencies such as MDC and MDA; Extension commercial clients include agriculture/crop consultants, landscape or lawn care companies and arborists; and Nonextension commercial clients include growers, farmers and private companies.

Figure 4 Counties submitting plant disease samples to the clinic in 2024.

Field Crops are the largest sample category with 296 samples, followed by deciduous ornamentals (139), small fruits (110), vegetables (78), evergreen ornamentals (35) and fruits (33) (Figure 5). Soybean (160), corn (83), wheat (47) and Industrial hemp (22) compose the four major crop categories (Figure 6).

Figure 5 Distribution of samples submitted for disease diagnosis by sample type.

Figure 6 Type of field crops submitted for disease diagnosis.

Thanks to the free wheat virus tests offered by the clinic, we have received 47 wheat samples which is a big leap of sample number comparing to 32 samples in 2023, and 10 samples received in 2022 (Table 2). We have tested for several wheat viruses positive in Missouri this year, including Wheat streak mosaic virus (WSMV), Wheat spindle streak mosaic virus (WSSMV), Soil-borne wheat mosaic virus (SBWMV), Barley yellow dwarf virus (BYDV), High Plains virus (HPV), and Cereal yellow dwarf virus (CYDV). The geographical information, disease and plant variety data had been collected to monitor the distribution of these viral diseases and plant resistance among different varieties and utilized for recommendations regarding disease management of 2025. 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.

Relatively wet conditions in the spring and early summer have posed challenges for early-season soybean growth and development. Several soybean samples submitted to the clinic were infected by multiple soil-borne pathogens such as Phytophthora crown and root rot, Pythium root rot and Rhizoctonia root and stem rot. Foliar diseases pressure is relatively low in the field, similar with the past three years and multiple leaf diseases are well controlled. However, we have seen large number of cases of late season soybean premature decline. Root rot diseases are confirmed to be involved in causing the yellowing and withering symptoms of soybeans, such as Charcoal Rot, Sudden Death Syndrome, Red Crown Rot, Brown Stem Rot, Pod and stem blight, Anthracnose as well as Stem borer (Table 2). We suspect that the environmental factors also played an important role in increasing stress to the plants.

Most corn samples submitted to clinic are for testing a relatively new disease called corn stunt disease (Table 2). So far this disease has been confirmed in multiple counties in Missouri, especially southern counties. However, little is known whether it can survive the winter this year. MU Plant Diagnostic Clinic is equipped with molecular assays and can confirm this disease within three business days.