Sample Diagnosis

In the first half of 2023, MU Plant Diagnostic Clinic received 232 samples and 125 sets of digital images submitted by email and online digital diagnosis platform. The 232 physical samples include services of plant disease diagnosis (210), insect identification (12), and plant identification (11). Disease diagnosis accounted for 91% of the total physical samples processed (Figure 1). There was an increase of 23% in physical sample numbers and 150% in digital sample numbers, compared to the year 2022. Like previous years, the lab received the most submissions in the summer months (Figure 2 and 3).

Figure 1 Number of physical samples by service type.

Figure 2 Number of physical samples analyzed by months.

Figure 3 Comparison of digital sample number between 2022 and 2023 from the month of January to June.

Sample Submission

232 in-state physical samples were received from 51 counties (Figure 4). 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 4 Counties submitted plant disease 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. Field Crops are the largest sample category with 101 samples, followed by Ornamentals (53) and vegetables (25). Soybean (48) and corn (14) compose the two major crop categories, followed by wheat (32) and industrial hemp (7) (Figure 5).

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

Figure 6 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, we received 14 Tomato samples followed by 8 Elderberry (Figure 7). 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. Disease management strategies of most of these diseases should be focused on sanitation and the use of resistant varieties.

Figure 7 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 in early 2023, causing prevalent environmental stress related problems for most of horticultural plants. Among all the samples, 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 deciduous and evergreen trees from multiple counties (Figure 6). The environmental stress of heat and drought throughout the start 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 in the first half of 2023 and similar incidence also occurred in vegetables, fruit trees and turfgrass. Fungal diseases that are normally prevalent in the dry weather include Fusarium root rot and Rhizoctonia crown and root rot, were detected from a few vegetable samples.

The drought conditions experienced in the past season exacerbated the issue of herbicide damage 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 a year with severe drought. Depending on the weather of this winter and spring of 2024, cold injury and excessive rainfall would worsen the situation of most ornamentals and vegetables while continuous drought would result in more environmental stress on all plants.

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 (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 plantclinic@missouri.edu.

We have a 4-minute video about sample submission guidelines on YouTube to help you submit your sample step by step. Please click here: https://youtu.be/XEWVT9lUflo.

Contact Information:

University of Missouri-Plant Diagnostic Clinic
28 Mumford Hall
Columbia, MO 65211
Phone: 573-882-3019
Email: plantclinic@missouri.edu
Twitter: https://twitter.com/MUplantclinic