It has been six months since MU Plant Diagnostic Clinic (MU-PDC) reopened on February 1st, 2021. The weather of the first half of the year was not very kind for many plants but very favorable for several fungal diseases. As of August 13th, 2021, The MU-PDC has received 214 samples including physical samples, walk-in samples and digital samples. Among all the samples, plant disease diagnosis accounted for the majority of the total samples while only three samples are for insect identification services and no sample for weed identification (Figure 1). Out of 211 disease diagnosis samples, 15 samples were suspected to have herbicide injury and 12 samples were confirmed with winter injury, indicating that the off-target chemical damage as well as cold injury played important roles in affecting plant health this year. The samples submitted to the clinic were also categorized based on the crop types (Figure 2). Ornamentals were the largest sample category with 71, followed by field crops (47) and turf (19).
The heavy rainfall early in the season increased the incidence of crown and root rot diseases for wheat, corn and soybean. We have confirmed 12 cases of Phytophthora crown and root rot diseases on soybean samples, 5 cases of corn Pythium crown and root rot and 2 cases of Rhizoctonia rot and eyespot disease on wheat. These diseases are primarily due to high moisture level in the soil. The prolonged cool and wet condition also triggered many foliar diseases or head blight diseases in the field crops, 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 four counties to date. So far, no bacterial or viral diseases were detected from corn and soybean in the field this year.
|Disease||Pathogen/Pests||# of samples|
|Anthracnose stem blight||Colletotrichum spp.||9|
|Herbicide injury||Abiotic disorder||2|
|Charcoal rot||Macrophomina phaseolina||1|
|Target spot||Corynespora cassiicola||1|
|Pod and stem blight||Diaporthe spp.||1|
|Pythium root and/or crown rot||Pythium sp./spp.||1|
|Phytophthora root rot||Phytophthora sojae||12|
|Soybean frogeye leaf spot||Cercospora sojina||1|
|Soybean thrips||Neohydatothrips variabilis||1|
|Spider mites||Family Tetranychidae||1|
|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||1|
|Southern leaf blight||Bipolaris maydis||1|
|Abnormal plant growth||Abiotic disorder||1|
|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|
|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|
|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 firstname.lastname@example.org.
We uploaded a webinar about sample submission guidelines on YouTube to help you submit your sample step by step.
Please click here: https://www.youtube.com/watch?v=4dUcYKKFwaI
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.
University of Missouri-Plant Diagnostic Clinic
28 Mumford Hall
Columbia, MO 65211
REVISED: August 19, 2021