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 2).

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.

Woody ornamentals including deciduous ornamentals (139) and evergreen ornamentals (35), compose the second largest group of the sample with field crops being on the top (Figure 5). Over 80% of the 110 small fruits are elderberry plants sent to the clinic for research use to identify foliar fungal and virus diseases. Tomato (40) and watermelon (11) are the two major vegetables among the rest of samples (Figure 6).

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

Figure 6 Type of vegetable/herbs/fruit crops submitted for disease diagnosis.

A certain amount of vegetable samples submitted by home gardeners and commercial growers were shown to be affected by chemical damage (suspected products containing Dicamba and 2,4-D) in the beginning of the season. Some Oomycete diseases such as Phytophthora or Pythium crown and root rot were found early in the season. Overall, root and crown rot diseases, vascular diseases and foliar diseases are three major plant health issues affecting the yield and quality through 2024. Disease management strategies for most of these diseases should be focused on sanitation and the use of resistant varieties.

Most Missouri counties experienced drought in the past few years. Environmental stress related problem is still a critical issue for woody ornamental plants especially evergreen trees such as spruce, pine, arborvitae and cypress. Many of them collected from multiple counties were diagnosed as abiotic diseases such as winter injury or drought stress. Others were diagnosed with fungal diseases such as needle cast and needle blight disease as well as insect damage by spider mites and scales.

In 2024, University of Missouri Extension's Plant Diagnostic Clinic, in partnership with the Missouri Department of Conservation (MDC), offered free testing for all common oak tree diseases. Almost 100 oak samples were received by the clinic, 13 of them were tested positive for Bacterial Leaf Scorch disease (BLS) and 9 samples were tested positive for Oak Wilt disease. Additional diseases detected are cicada damages, canker, mechanical injury, oak leaf gall, tubakia leaf spot, etc. This project is meaningful to track the most severe diseases for oak trees in urban areas. Meanwhile it allowed the clinic to implement a novel molecular assay to test BLS and Oak Wilt diseases from oak leaf tissues directly, which drastically increase the efficiency of the oak disease testing.

Other ornamentals such as shrubs, annuals and perennials did not show many diseases in 2024 except boxwood, which continued to show symptoms of stress from both abiotic and biotic factors. The clinic has confirmed the presence of Spider mite injury, Macrophoma leaf spot, leafminer and Volutella blight among the submitted boxwood samples.

For appropriate diagnosis, the MU Plant Diagnostic Clinic can help you confirm if your plant has this disease. We encourage you to visit our website and review submission guidelines before submitting your sample. If possible, you may take photos and send them to plantclinic@missouri.edu.

We have a 7-minute video about sample submission guidelines on YouTube to help you submit your sample step by step.