Using a hand lens to scout for strawberry disease signs in the field. Photo: Jennie Mazzone, Penn State

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Strawberry diseases can quickly reduce yield and fruit quality if problems go unnoticed. Regular scouting and accurate diagnosis are key to identifying problems early and managing diseases effectively in your berries. When you notice a problem, look closely at the plant for both symptoms and signs. A symptom is a visible change in a plant’s appearance that occurs in response to stress, whether from disease or something else (e.g. environmental stress, insect damage), and is often the first indication that something is wrong with the plant. Common disease symptoms include yellowing, browning, wilting, etc. Signs are visible structures of a disease pathogen. Pathogen signs you can see with the naked eye or that may require a hand lens include fungal growth, spore structures, and bacterial ooze. Use the following step-by-step guide to identify common strawberry diseases based on the location of symptoms and the characteristic signs present on affected plants. Keep in mind that a plant can have more than one disease at the same time, so symptoms may be caused by multiple problems rather than a single disease.

1. Are whole plants collapsing?

Root rot, vascular wilt, and crown rot diseases can cause whole strawberry plants to collapse. Many of these diseases do not make visible signs in the field and require laboratory testing for diagnosis. These diseases include:

Black root rot (Rhizoctonia, Pythium, Fusarium, nematodes)

Symptoms: stunting, chlorosis, collapse, black roots with "rat-tail" appearance

Signs: absent in field, multiple pathogens

Side-by-side images of strawberry black root rot. Left: several strawberry plants in a plastic-mulched row showing collapsed foliage and dead or dying leaves compared to nearby green plants. Right: close-up of roots with extensive dark brown to black discoloration, indicating root decay characteristic of black root rot. — Figure 1. Side-by-side images of black root rot disease on strawberry. Left: several strawberry plants in a plastic-mulched row showing collapsed foliage and dead or dying leaves. Credit: Jennie Mazzone, Penn State. Right: close-up of roots with extensive dark brown to black discoloration, indicating root decay characteristic of black root rot. Credit: Kathy Demchak, Penn State.

Red stele and Phytophthora crown rot

Symptoms: wilt, collapse, reddish-brown crown, brown central stele of root when split lengthwise

Signs: absent or white cottony growth (rare)

Left: Strawberry plants in a plastic-mulched field showing collapse and dead foliage caused by Phytophthora. Right: A strawberry crown and root system cut lengthwise, revealing reddish-brown discoloration of the crown and central root stele, a characteristic symptom of Phytophthora infection. — Figure 2. Side-by-side images of *Phytophthora* disease of strawberry. Left: strawberry plants affected by *Phytophthora* show collapse and plant death. Right: infected crowns and roots exhibit characteristic reddish-brown discoloration when cut lengthwise. Credit: Kathy Demchak, Penn State.

Verticillium wilt

Symptoms: wilting and drying of outer leaves first

Signs: absent in field

Strawberry plants showing collapse, wilting, and drying of outer leaves caused by Verticillium wilt disease. — Figure 3. Strawberry plants infected with *Verticillium* wilt exhibit collapse, wilting, and drying of outer leaves, resulting in reduced vigor and plant decline. Credit: Jay W. Pscheidt, Oregon State University.

Anthracnose crown rot (Colletotrichum gloeosporioides and fragariae)

Symptoms: wilting, stunting, collapse, red and white marbling of crown, scorch, circular black leaf spots, petiole rot

Signs: salmon-orange spore masses (acervuli)

The left image shows a strawberry crown cut lengthwise with red and white marbled crown. The right image shows a leaf petiole with a necrotic lesion and signs of orange fungal spore masses within lesion. — Figure 4. Side-by-side images of anthracnose crown rot on strawberry. Left: a lengthwise section of an infected strawberry crown shows the characteristic red-and-white marbled discoloration associated with anthracnose crown rot. Credit: Kathy Demchak, Penn State. Right: a necrotic lesion on a leaf petiole contains signs of orange fungal spore masses. Credit: Steve Koike, TriCal Diagnostics.

Neopestalotiopsis

Symptoms: tan-brown circular leaf spots with dark margins become irregular and v-shaped, orange-brown crown rot, sunken tan fruit rot may appear black with signs of the fungus

Signs: black, eyelash or tentacle-like spore masses (acervuli)

Composite image showing strawberry plants affected by Neopestalotiopsis. The left image shows a strawberry crown cut lengthwise with orange-brown to dark brown internal crown rot and necrotic tissue. The right image shows a strawberry planting with scattered dead and declining plants, brown collapsed foliage, and tan-brown irregular leaf spots. — Figure 5. Side-by side images of *Neopestalotiopsis* disease on strawberry. Left: a lengthwise section of an infected strawberry crown shows orange-brown internal crown rot. Credit: Kathy Demchak, Penn State. Right: *Neopestalotiopsis* causing plant decline, collapsed brown foliage, and irregular tan-brown leaf spots. Credit: Jennie Mazzone, Penn State.

Microscopic image showing black spore masses of Neopestalotiopsis fungus. — Figure 6. Microscopic image showing signs of black, tentacle-like spore masses of *Neopestalotiopsis* fungus. Credit: Kathy Demchak, Penn State.

*Winter injury

Symptoms: widespread plant discoloration and collapse, crown flecking or "corkiness", solid pink or reddish color

Signs: absent, *Not a disease

*Note: Winter injury is an abiotic (nonliving) disorder rather than a disease, but it is often mistaken for disease due to similar symptoms. Reviewing recent weather patterns, winter conditions, and field history can help distinguish winter injury from infectious diseases.

Composite image showing winter injury in strawberries. The left image shows a strawberry crown cut lengthwise with internal pink to reddish discoloration and flecking, giving a corky appearance characteristic of winter damage. The right image shows a plasticulture strawberry row with widespread plant collapse, dead foliage, and uneven plant survival following winter injury. — Figure 7. Side-by-side images of winter injury, an abiotic disorder, on strawberry. Left: a strawberry crown cut lengthwise with internal pink to reddish discoloration and flecking, giving a corky appearance characteristic of winter damage. Credit: Kathy Demchak, Penn State. Right: widespread plant collapse, dead foliage, and uneven plant survival following winter injury. Credit: Jennie Mazzone, Penn State.

2. Do symptoms appear mostly on foliage?

Leaf spot diseases reduce photosynthesis and can reduce yield. Some of these diseases also infect other parts of the plant including petioles, runners, and fruit. These diseases include:

Phomopsis leaf blight

Symptoms: red circular spots with purple margin advancing to v-shaped brown blotch with yellow, red, and purple margins

Signs: black, pimple-like, globose fruiting bodies (pycnidia) with ostiolar neck (pore-bearing) oozing cream color spore tendril

Strawberry leaf showing small red to purple circular spots and larger, v-shaped blotches bordered by yellow, red, and purple margins caused by Phomopsis leaf blight. — Figure 8. Strawberry leaf showing small red to purple circular spots and larger, v-shaped blotches bordered by yellow, red, and purple margins caused by *Phomopsis* leaf blight. Credit: Jennie Mazzone, Penn State.

Microscopic image showing black fruiting bodies of Phomopsis fungus. Two fruiting bodies on left are mature and oozing spore masses. Two fruiting bodies on the right are immature and show ostiolar neck. — Figure 9. Microscopic image of *Phomopsis* fruiting bodies, which appear as small, pimple-like signs of the pathogen. Two fruiting bodies on left are mature and oozing spore masses. Two fruiting bodies on the right are immature and show ostiolar neck. Credit: Jennie Mazzone, Penn State.

Gnomonia leaf blotch

Symptoms: large tan-brown blotches with dark margins, often beginning at leaf margin

Signs: yellow-brown fruiting bodies (pycnidia) with NO ostiolar neck

Strawberry leaf showing Gnomnia leaf blotch disease causing large tan-brown blotches with dark margins, originating at the leaf margin. — Figure 10. Strawberry leaf showing *Gnomonia* leaf blotch disease causing large tan-brown blotches with dark margins, originating at the leaf margin. Credit: David Lawrence, Alabama Cooperative Extension System.

Microscopic image showing two brown Gnomonia fungal fruiting bodies on a strawberry leaf. — Figure 11. Microscopic image of brown *Gnomonia* fungal fruiting body signs on a strawberry leaf. Credit: Jennie Mazzone, Penn State.

Diplocarpon leaf scorch

Symptoms: irregular, purple to brown blotches, with tissues in between lesions turning purple to red

Signs: black, disc-shaped fruiting bodies (acervuli) develop on upper leaf surfaces

Strawberry leaf showing leaf scorch symptoms of irregular, purple to brown spots, with purple to red discoloration between lesions. — Figure 12. Strawberry leaf scorch symptoms of irregular, purple to brown spots, with purple to red discoloration between lesions. Credit: Kathy Demchak, Penn State.

Microscopic image showing black, disc-shaped fruiting bodies of Diplocarpon fungus on a strawberry leaf. — Figure 13. Microscopic image showing signs of black, disc-shaped fruiting bodies of *Diplocarpon* fungus on a strawberry leaf. Credit: Matt Bertone, North Carolina State University.

Ramularia (Mycosphaerella) common leaf spot

Symptoms: white, circular, birds-eye leaf spots with gray center and reddish-purple margins

Signs: masses of tan-white chains of spores (conidiophore)

Figure 14. Strawberry leaf showing white, circular leaf spots with reddish-purple margins caused by common leaf spot. Credit: Kathy Demchak, Penn State.

Microscopic image showing white spore structures of Ramularia fungus on strawberry leaf. — Figure 15. Microscopic image showing signs of white spore structures of *Ramularia* fungus on strawberry leaf. Credit: Kathy Demchak, Penn State.

Angular leaf spot

Symptoms: water-soaked, translucent, or brown angular leaf spots restricted by leaf veins; brown fruit calyx

Signs: absent or cream to amber bacterial ooze in very moist conditions (dries as shiny scales/crusts)

Composite image of strawberry angular leaf spot symptoms. Main image shows strawberry leaves with numerous angular, water-soaked lesions that have become translucent, brown, and necrotic, with yellowing tissue in between lesions. An inset image shows a developing strawberry fruit with a dark brown, dried calyx (cap) and sepals. — Figure 16. Composite image of strawberry angular leaf spot symptoms. Main image shows strawberry leaves with numerous angular, water-soaked lesions that are translucent or brown, with yellowing tissue in between lesions. An inset image shows a developing strawberry fruit with a dark brown, dried calyx (cap) and sepals. Credit: Kathy Demchak, Penn State.

Microscopic image showing amber colored bacterial ooze from angular leaf spot lesions on strawberry leaf. — Figure 17. Microscopic image showing signs of amber colored bacterial ooze from angular leaf spot lesions on strawberry leaf. Credit: Kathy Demchak, Penn State.

Powdery mildew

Symptoms: upward leaf curl, purple/red leaf margins

Signs: white fuzzy mold (mycelium and conidiophores) on lower leaf surface

Figure 18. Upward leaf curl, red leaf margins, and white fungal signs of powdery mildew disease on the lower leaf surface of strawberry. Credit: Jennie Mazzone, Penn State.

3. Do symptoms appear mostly on fruit?

Strawberry fruit rots primarily infect flowers and developing fruit, causing soft or decayed berries that are unmarketable. Although these diseases may infect other plant parts (e.g. petioles, leaves), they are characterized by their fruit rot symptoms and significant impact on fruit quality and yield. These diseases include:

Botrytis gray mold

Symptoms: fruit rot, blight, crown rot on stressed plants

Signs: dense gray fuzzy sporulation on tree-like stalks (conidiophore)

Gray sporulation of Botrytis fungus on strawberry fruit. — Figure 19. Signs of gray sporulation of *Botrytis* fungus on strawberry fruit. Credit: Jennie Mazzone, Penn State.

Anthracnose fruit rot (Colletotrichum acutatum)

Symptoms: firm, sunken brown/black fruit lesions, blackened seeds

Signs: salmon-orange spore masses (acervuli)

Anthracnose fruit rot causing sunken lesions with masses of orange spores within the lesion. — Figure 20. Anthracnose fruit rot causing sunken lesions and blackened seeds with signs of orange spore masses within the lesion. Credit: Kathy Demchak, Penn State.

3. Do you see symptoms and no signs?

If you strongly suspect disease, but no pathogen signs are visible, place symptomatic plant tissue in a moist chamber by wrapping it in a damp paper towel and sealing it in a plastic bag. Check the tissue over the next few days, as many fungal pathogens will produce visible growth under these conditions.

If no pathogen signs develop, consider other causes of plant decline, such as insect pests, winter injury, nutrient deficiencies, or other abiotic stresses.

Plant disease signs can be difficult to detect because they are very small, requiring a high-magnification hand lens (40X) or microscope to observe, and may only appear under certain environmental conditions. If you need help with diagnosis, contact your local Extension office or submit a sample to the Penn State Plant Disease Clinic.

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