Sample highlights

Current samples

Sample highlights archive

View Now

Cercospora Leaf Blight of Soybean

Morgan Goodnight and Peng Tian

In 2021, the MU Plant Diagnostic Clinic received seven soybean samples diagnosed with Cercospora Leaf Blight (CLB). These disease samples were collected from the counties including Vernon, Cooper, Montgomery, Chickasaw, Clark, and Johnson, and most of them were submitted to the MU Plant Diagnostic Clinic toward the end of the growing season. Symptoms of this disease present as severe leaf dropping and premature death. In addition to CLB, we also found other diseases such as charcoal rot, potassium deficiency and anthracnose present on several soybean samples.

cercospora leaf blight

Symptoms and signs: The symptom of this disease begins as purple, brownish spots on leaves. As it progresses, these leaf spots deepen in color and combine to form large necrotic areas that eventually lead to premature defoliation (Figure 1). In addition to significant yield loss resulted from defoliation, this disease can also cause purple seed stain which severely affects the product quality. Cercospora kikuchii produces septate conidiophores with size of 200-300 µm long and 4-5 µm wide while the size of conidia is 170 to 190 µm long and 3 µm wide.

Learn more about the life cycle, damage and management of this disease:

Full version (PDF)


Black Canker of Weeping Willow

Peng Tian

Black Canker of weeping willow is caused by a fungus called Glomerella miyabeana and this disease is one of common willow diseases. Glomerella miyabeana and the other fungus Venturia saliciperda, the causal agent of willow scab disease together can result in a serious disease called willow blight.

black canker

Symptoms and signs: Symptoms usually begin as brown to black lesions on the leaves in the early spring. As the disease progresses, these lesions expand to the whole leaf and spread to the petiole. The leaves turn brown and wilt and eventually fall off the stem. Once the lesion spread to the stem or twig, this disease can cause black colored cankers with various size, normally in the junction position of twig and petiole (Figure 1). Once these cankers become mature, black fruiting bodies called acervuli developed on the canker and produce asexual spores called conidia.

Learn more about the life cycle and management of this disease:

Full version (PDF)


Tubakia Leaf Spot on Oak

John W. Howard II and Peng Tian

An excessively wet spring, a late frost and a moderate summer contributed to increased incidence of Tubakia leaf spot disease on oak trees this year. This disease predominantly infects Oak species with latent symptoms of dark red to brown spots on leaves appearing in mid to late summer. For appropriate diagnosis, the MU Plant Diagnostic Clinic can help you confirm if your plant has this fungal disease.

tubakia leaf spot on oak

Symptoms and signs: Typical symptoms are circular leaf spots that are dark red to brown ranging from ¼ to ½ inch in diameter (Figure 1). The leaf spots occurring on leaf veins result in vascular collapse and tissue death with severe cases causing early defoliation. Heavily congregated Tubakia leaf spots are often confused as Oak wilt or Anthracnose disease. The spores of Tubakia spp. are microscopic and cannot be seen unaided, thus proper identification requires analysis with a laboratory microscope. Tubakia spp. have a unique fruiting structure called pycnothyrium that composes of a shield like scutellum of radial projected hyphae. The scutellum is supported by a short columnar stalk that bears the round to ovoid conidia spores.

Learn more about the life cycle and management of this disease:

Full version (PDF)


Leaf Spot on Lilac

Morgan Goodnight and Peng Tian

The MU Plant Diagnostic Clinic received several lilac samples this summer that all showed leaf spot and leaf drop/blight symptoms caused by the fungi called Pseudocercospora spp. This pathogen favors shaded areas and humid weather, which Missouri has experienced quite often in this summer.

leaf spot on lilac

Symptoms and signs: Symptoms usually begin as brown spots on the leaves that begin at the edges and move inward (Figure 1). As the disease progresses, it causes leaf curling, leaf blight and eventually leaf dropping once the leaf is completely infected.

Learn more about the life cycle and management of this disease:

Full version (PDF)


Red Clover Rust

Morgan Goodnight and Peng Tian

The weather of this spring has been cooler and wetter than the past, which provided great conditions that favor many different types of fungal diseases. As one of important foliar diseases of a broad range of hosts including field crops and ornamental plants, rust diseases weren't left out from this party. The staff at MU Plant Diagnostic Clinic recently received a red clover sample that was confirmed being infected by a rust disease, which was added to an already-full list of these fascinating basidiomycetes.

red clover rust

Symptoms and signs: Symptoms usually begin as yellow spots all over the leaves and stems (Figure 1). Once they become mature, these spots turn red or brown and develop into pustules that are about 2 mm long (Figure 2). These pustules can develop along the stem and over/under the leaves, and cause twisting of the stem, leaf distortion or defoliation in some cases.

Learn more about the life cycle and management of this disease:

Full version (PDF)