Sample Diagnosis

In 2023, MU Plant Diagnostic Clinic received a total of 901 physical samples and 253 sets of digital images submitted by email and online digital diagnosis system. There was an increase of 135% in physical samples and 66% in digital samples, compared to the year 2022 (Figure 1 and figure 2). Among physical samples submission for services including plant disease diagnosis, insect, weed, and plant identification, disease diagnosis accounts for 55% of the total physical samples processed (Figure 3). 372 elderberry samples, accounting for 41% of the total physical samples are for research project funded by Missouri Department of Agriculture Specialty Crop Block Grant Program. Like previous years, the lab received the most submissions in the summer months (Figure 1, 2 and 4).

Figure 1 Number of physical samples processed by month in 2022 and 2023.

Figure 2 Number of digital samples processed by month in 2022 and 2023.

Figure 3 Number of physical samples by service type.

Figure 4 Number of physical samples analyzed by month.

Sample Submission

872 in-state physical samples were received from 78 counties (Figure 5 and figure 6). 76% of the samples were submitted by commercial clients. Submission received directly from educators and homeowners accounted for 19% of the total physical samples processed in 2023. Figure 5 shows counties account for the 500 in-state submissions excluding elderberry research samples and figure 6 shows which counties the elderberry research samples were submitted from.

Figure 5 Counties submitted plant disease samples to the clinic excluding research samples.

Figure 6 Counties submitted elderberry research samples to the clinic.

Sample Category

Samples submitted to the clinic were categorized into different crop types such as field crops, turf, ornamentals, vegetables, and fruits. Fruits are the largest sample category with 404 samples due to 372 research samples, followed by field crops (265), ornamentals (124), vegetables (55), turfgrasses (4), and Other (20) (Figure 7). Woody ornamental plants including evergreen and deciduous plants account for 80% of the total submissions (Figure 8).

Figure 7 Distribution of samples submitted for disease diagnosis by sample category.

Figure 8 Summary of the types of Ornamental Plants submitted to the clinic.

Summary of Fruit and Vegetable Crop Diagnosis

Among the diagnosed fruit and vegetable samples excluding elderberry, we received 35 Tomato samples followed by 4 Apple samples (Figure 9). Some vegetable samples submitted by home gardeners and commercial growers were shown to be affected by chemical damage (suspected Dicamba and 2,4-D products) in the beginning of the season. Root and crown rot diseases and foliar diseases were two major health issues affecting the yield and quality through the season, with fusarium root rot becoming prevalent towards the end of the growing season. Disease management strategies of most of these diseases should be focused on sanitation and the use of resistant varieties.

Figure 9 Summary of the types of Fruit and vegetable samples submitted to the clinic.

Most Missouri counties experienced drought for several months in 2022 and the drought continued into 2023, causing prevalent environmental stress related problems for most horticultural plants. Early in the year, very few fungal or bacterial diseases were detected due to lack of favorable living conditions. Drought stress related problems for woody ornamental plants were prevalent as the clinic observed several submissions of diseased samples of both deciduous and evergreen trees from multiple counties (Figure 8). The environmental stress of heat and drought throughout the beginning of the year can cause needle yellowing and stem dieback. Symptoms may vary among different families of trees and may take one or two following seasons to appear. Once the symptoms appear in woody plants, the disease or stress is beyond treatment. Clients may consider keeping good irrigation for their trees even in the winter, performing a soil test early in the spring for recommendations regarding soil fertilization, and pruning dead branches when the trees are still dormant.

Other ornamentals such as shrubs, annuals and perennials did not show many diseases through 2023 and similar incidence also occurred in some vegetables, fruit trees and turfgrass. Intermittent rains late in the season led to the detection of oomycete diseases such as root and crown rot following moist conditions due to plant stress presented before precipitation.

The drought conditions experienced in the past season exacerbated the issue of herbicide damage in the first half of this year. With limited rainfall and lack of soil moisture, the normal breakdown of herbicides in the soil was delayed. As a result, herbicide residues persisted for longer periods, leading to increased damage to crops and vegetation. The lack of moisture also reduced plant vigor, making them more susceptible to herbicide and other disease stress and hindering their ability to recover by adverse conditions.

It is always hard to predict the performance of the plants and prevalence of plant diseases right after multiple years with severe drought. The fall and winter of 2023 was mild and dry except for a period of extreme cold at the beginning of 2024. The freeze in culmination with previous conditions may lead to cold damage to ornamental plants in the upcoming growing season. If drought continues throughout this spring, all plants may be environmentally stressed again due to these conditions.

MU Plant Diagnostic Clinic is here to help you confirm if your plants are diseased. We encourage you to visit our website https://extension.missouri.edu/programs/plant-diagnostic-clinic and review submission guidelines before submitting your sample. If possible, you may take photos and send them to our email address: plantclinic@missouri.edu.

We just launched a new video, https://www.youtube.com/watch?v=9g312_U1iiI, about sample submission guidelines on YouTube to help you submit your sample step by step.

For sample submission and fee payment

Visit our new online submission system at https://extension.missouri.edu/products-and-services/plant-disease-sample. Fill out the submission form online using your computer or mobile device and make payment online securely with a credit card.

OR

Download the submission form at https://extension.missouri.edu/programs/plant-diagnostic-clinic/sample-submission. Fill it out and send to us together with your sample and payment. Check or money order. No cash please.

University of Missouri-Plant Diagnostic Clinic