Current samples

Wheat Streak Mosaic Virus

Pierce Taylor and Peng Tian

Wheat streak mosaic virus (WSMV) is a plant virus that infects wheat and other cereal crops, causing significant economic losses in many regions of the world. WSMV is a serious threat to global food security, as it can significantly reduce crop yields and limit the availability of wheat and other cereal crops for food and feed. WSMV is part of the family Potyviridae, which includes many other economically significant plant viruses. WSMV is transmitted by a tiny, winged insect called Wheat Curl Mite (Aceria tosichella) (WCM), which can easily spread the virus from plant to plant.

Symptoms and signs: Symptoms of WSMV infection include characteristic yellow streaks on the leaves of infected plants. As the infection progresses, leaves take on a mottled appearance which can eventually lead to stunted growth, reduced yields, and even plant death in severe cases. Severity of the disease depends on plant age at the time of infection, environmental conditions. Warm (75-80°F, 24-27°C), dry weather promotes infection by stressing plants and encouraging the proliferation of the primary vector, the WCMs.

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Wheat Spindle Streak Mosaic Virus (WSSMV) and Soil-borne Wheat Mosaic Virus (SBWMV)

Pierce Taylor and Peng Tian

Both Wheat Spindle Streak Mosaic Virus (WSSMV) and Soil-borne Wheat Mosaic Virus(SBWMV) are soil-borne viruses that infect wheat and other cereal crops, causing significant yield losses in many parts of the world. As the name suggests, SBWMV is primarily transmitted through soil, either through direct contact with infected plant debris or via soil-dwelling vectors like Polymyxa graminis, a fungus-like organism that can spread the virus to new plants.

Wheat Spindle Streak Mosaic Virus and Soil-borne Wheat Mosaic Virus

Symptoms and signs: Symptoms of WSSMV and SBWMV infection can vary depending on the strain of the virus and the stage of plant growth, but can include yellowing, mosaic or mottling patterns on the leaves, stunted growth, and reduced grain quality. WSSMV can cause light green to yellow spindle-shaped streaks and necrosis of leaves, reduced heading, and slight stunting while the symptoms of SBWMV are chlorotic mosaic or irregular mottling and streaking, and even resetting in some very susceptible cultivars. Symptoms are most prominent on early-spring growth and rarely appear in the fall.

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Barley Yellow Dwarf Disease of Wheat

Pierce Taylor and Peng Tian

In Missouri, barley yellow dwarf (BYD) is a disease that can infect a wide range of cereal crops, primarily barley, wheat, oats, and rye. The disease is a significant threat to cereal production worldwide, with estimated losses of up to $1 billion annually, causing yield loss between 11% and 33% and sometimes up to 80% (Miller and Rasochová 1997). Viruses that cause this disease are commonly referred to as barley yellow dwarf virus (BYDV), maize yellow dwarf virus (MYDV) and cereal yellow dwarf virus (CYDV) and belong to different genera in the same family Luteoviridae (Walls III et al). This disease primarily spread by over 20 types of aphids, which feed on infected plants and then transmit the virus to healthy plants as they move between fields.

Symptoms and signs: Symptoms of infection includes yellowing or reddening of leaves, stunted growth, and reduced yield and quality and can vary depending on the crop and the severity of the infection. Vigilant monitoring and management practices are essential for minimizing the impact of the disease on farmers and food security. Typically, BYD disease causes discoloration at the leaf edges and midrib before the leaf tip. Leaves become light green or yellow and may have apparent purple staining.

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Phyllosticta Needle Blight

Pierce Taylor and Peng Tian

Phyllosticta Needle Blight, caused by Phyllosticta thujae, is a fungal pathogen which primarily infects Arborvitae. The majority of Phyllosticta species are regarded as secondary pathogens on conifers, and many of them are poorly understood. While the infection may not cause death of the tree, the browning needle tips caused by P. Thujae are unsightly for homeowners and landscape designers. Phyllosticta thujae is frequently seen after stressful events that weaken a tree's defenses against pathogen infection. Winter injury, drought stress, excessive pruning, etc. are a few examples of common stressors which lead the pathogen to take hold.

phyllosticta needle blight

Symptoms and signs: Plants infected with P. thujae generally have blighted needle tips and/or discolored (pale green to yellow) needles that appear dry (Figure 1). Infections frequently start at the needle's tip and spread to the base. When the weather is damp and moderate, black fungal tissue pads called pycnidia burst through the epidermis on symptomatic needles to release vast amounts of spores called conidia, which are then splashed or blown to surrounding shoots to start new infections. The dense canopies of arborvitae, especially those that have been sheared, provide the optimum environment for the growth of pathogens.

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Botrytis Blight of Peony

Dawshaia Herndon, Morgan Goodnight and Peng Tian

The MU Plant Diagnostic Clinic received a peony sample that was diagnosed with Botrytis Blight. It is a very common disease that tends to appear in seasons of conditions with high moisture and warm temperatures. By establishing itself in dead plant matters and forming survival structures, this disease can survive harsh weather in the winter. However, this disease can be controlled and prevented through proper management techniques.

botrytis blight peony

Symptoms and signs: This disease causes symptoms on peonies such as leaf spots, wilting shoots, blackened buds, stem discoloration as well as grey mold (Figure 1). It first starts on the new shoots, causing wilting and discoloration (brown/black). As the disease progresses, it spreads on flower buds, causing the buds to swell and die without opening in severe cases. Meanwhile, it also causes leaf spots and stems discoloration as infected leaves and buds fall off and touch healthy leaves on the way down.

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

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Sample highlights archive

Check out previous highlights from the Plant Diagnostic Clinic.