MU Plant Diagnostic Clinic reopened in February 1st, 2021. From February to December 2021, the clinic has received 276 physical samples and 61 digital samples. Among all the samples, plant disease diagnosis accounted for the majority of the total samples while five samples are for insect identification services and two samples for weed identification (Figure 1). The physical samples submitted to the clinic were categorized based on the plant types (Figure 2). Ornamentals are the largest sample category with 99, followed by field crops (72) and vegetables (39). Soybean (22) and corn (20) compose the two major crop categories, followed by hemp (13) and wheat (8) (Figure 3).
Figure 1 Number of samples by service type
Figure 2 Number of samples by sample type
Figure 3 Number of field crop samples by sample category
Crown and root rot diseases caused by Phytophthora spp. and Pythium spp. were prevalent early in the season due to the heavy rainfall as well as the late frost weather in the spring. We have reported 13 cases of Phytophthora root rot diseases on soybean samples and 5 cases of Pythium crown and root rot on corn, primarily due to high moisture level in the soil. The prolonged cool and wet condition also triggered many foliar diseases or head blight diseases, such as wheat leaf rust, wheat scab, wheat blotch, soybean frogeyes leaf spot, septoria leaf spot, corn gray leaf spot and southern rust (Table 1). Tar spot disease is a relatively new disease to Missouri and has been confirmed in 8 counties in the northeast of the state this year, showing a tendency to move south and west. We also confirmed purple see stain and leaf blight disease caused by Cercospora kikuchii from 8 soybean samples. This disease can cause severe leaf dropping and premature death, thus it certainly is a disease to watch out in the new growing season.
Table 1 A list of diseases and pests diagnosed on agronomic crops in 2021
| Disease | Pathogen/Pests | # of samples |
| Soybean | ||
| Anthracnose stem blight | Colletotrichum spp. | 9 |
| Herbicide injury | Abiotic disorder | 2 |
| Charcoal rot | Macrophomina phaseolina | 4 |
| Target spot | Corynespora cassiicola | 1 |
| Pod and stem blight | Diaporthe spp. | 2 |
| Pythium root and/or crown rot | Pythium sp./spp. | 1 |
| Phytophthora root rot | Phytophthora sojae | 13 |
| Soybean frogeye leaf spot | Cercospora sojina | 3 |
| Purple seed-stain; Leaf blight | Cercospora kikuchii | 8 |
| Soybean downy mildew | Peronospora manshurica | 2 |
| Soybean brown stem rot | Phialophora gregata | 1 |
| Soybean thrips | Neohydatothrips variabilis | 1 |
| Spider mites | Family Tetranychidae | 1 |
| Unidentified agent | Unknown | 2 |
| Corn | ||
| Corn gray leaf spot | Cercospora zeae-maydis | 1 |
| High moisture | Abiotic disorder | 6 |
| Pythium root and/or crown rot | Pythium sp./spp. | 5 |
| Southern corn rust | Puccinia polysora | 2 |
| Bacterial stalk and top rot | Erwinia carotovora | 1 |
| Spider mite | Tetranychus sp./spp. | 1 |
| Physoderma brown spot | Physoderma maydis | 1 |
| Corn tar spot | Phyllachora maydis | 3 |
| Southern leaf blight | Bipolaris maydis | 1 |
| Abnormal plant growth | Abiotic disorder | 1 |
| Mold; Mildew | Trichoderma sp./spp. | 2 |
| Red root rot | Phoma terrestris | 5 |
| Wheat | ||
| Head Blight | Fusarium graminearum | 5 |
| Rhizoctonia crown and root rot | Rhizoctonia solani | 1 |
| Root rot and sharp eyespot | Rhizoctonia cerealis | 1 |
| Pythium root and/or crown rot | Pythium sp./spp. | 2 |
| Wheat blotch | Parastagonospora nodorum | 2 |
| Anthracnose | Colletotrichum graminicola | 1 |
| Fusarium root rot | Fusarium sp./spp. | 1 |
| Wheat bacterial leaf blight | Pseudomonas syringae pv. syringae | 1 |
| Environmental stress | Abiotic disorder | 1 |
| Stripe rust; Yellow rust | Puccinia striiformis var. striiformis | 2 |
| Unidentified agent | Unknown | 3 |
| Forage, Alfalfa & Clover | ||
| Cercospora leaf spot | Cercospora sp./spp. | 1 |
| Leptosphaerulina leaf spot | Leptosphaerulina sp./spp. | 1 |
| White mold (Stem rot) | Sclerotinia sclerotiorum | 1 |
| Fusarium root; Crown rot | Fusarium spp. | 1 |
| Clover rust | Uromyces trifolii | 1 |
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 just uploaded a new 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.
For sample submission and fee payment, you can either:
1) Visit our new online submission system at https://extension.missouri.edu/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.
2) 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.
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