Root and Crown Rot Diseases on the Rise in Wisconsin Strawberries
This season, strawberry growers across Wisconsin have seen an uptick in root and crown rot diseases—particularly Phytophthora crown rot and black root rot—leading to plant collapse, poor vigor, and uneven stand establishment. While some symptoms may appear above ground as wilting or stunting, the real damage is happening below the surface, and accurate diagnosis is key to managing these threats effectively. As we move into the second half of the growing season, understanding how to scout, diagnose, and respond to these diseases is critical.
Similar Symptoms, Different Pathogens
One of the biggest challenges with root and crown rots is that above-ground symptoms often look the same across multiple diseases. Stunted growth, poor runner development, off-color foliage, and early plant death are common red flags—but the cause may differ. Growers are encouraged to consider soil type, drainage, field history, planting age, and cut into roots and crowns to observe internal symptoms. Sending samples to the UW Plant Disease Diagnostic Clinic is the best way to confirm the specific pathogen(s) at play.
Phytophthora Crown Rot (Phytophthora cactorum)
Favored by saturated soils and poor drainage, Phytophthora crown rot causes sudden wilting, plant collapse, and firm, brown discoloration in the crown. It spreads through soil and irrigation water, and infected crowns may rot from the inside out. This pathogen is difficult to manage once established but can be suppressed using fungicide drenches (e.g., Ridomil Gold, phosphonates like Aliette) and by improving field drainage.
Red Stele (Phytophthora fragariae)
Often confused with black root rot, red stele is diagnosed by cutting into roots and observing a brick-red central core (stele). Symptoms typically appear during cool, wet springs or falls, often in the second year after planting. Affected plants are stunted, and lateral root growth is sparse. The pathogen survives in soil for over a decade, and the varieties ‘Jewel’, ‘Honeoye’, and ‘Kent’ are among the most susceptible. Resistant varieties like ‘Earliglow’, ‘Allstar’, and ‘Mesabi’ can help reduce risk, though no cultivar is immune to all races.
Black Root Rot Complex
This disease results from a combination of fungi (e.g., Rhizoctonia, Fusarium, Pythium), nematodes, and environmental stress factors like compaction or poor soil health. Infected plants show blackened roots, missing feeder roots, and a white stele (differentiating it from red stele). Black root rot tends to appear in older fields (3–4 years or more) and is favored by continuous strawberry production in the same field. There are no chemical cures; site rotation, improved soil health, and tolerant varieties like ‘Dickens’ are the best management tools.
Verticillium Wilt
This soilborne fungus infects vascular tissue and has a very wide host range, including potatoes, tomatoes, cucurbits, and raspberries. Symptoms include leaf marginal browning, poor leaf emergence, and eventual dieback. Plants infected early are also more susceptible to winter injury. It’s most active in cool soils but symptoms emerge in early summer. Avoid planting in fields recently cropped to Verticillium hosts, and use tolerant varieties such as ‘Allstar’, ‘DelMarvel’, and ‘Earliglow’.
Neopestalotiopsis Crown and Root Rot
A newer and emerging threat, Neopestalotiopsis has only been reported a few times in Wisconsin but is spreading rapidly in warmer production regions. This aggressive pathogen infects all plant tissues—roots, crowns, fruit, and leaves—and is often introduced through infected transplants. Symptoms include darkened roots and orange-brown crown rot. Disease development is strongly favored by warm, wet conditions (77–86°F) and extended leaf wetness. There are currently no resistant varieties, and prevention is key. Disinfect field equipment, avoid working in wet fields, and monitor transplant health closely.
Best Practices for Managing Root & Crown Diseases
- Get an Accurate Diagnosis
- Send samples to the UW Plant Disease Diagnostic Clinic.
- Include roots, crowns, and above-ground tissues from multiple plants and infection stages.
- Note field history and environmental conditions.
- Choose the Right Site
- Avoid low-lying areas or poorly drained soils.
- Use raised beds and improve field drainage where possible.
- Rotate fields out of strawberries for at least three years, especially after red stele, Verticillium, or black root rot.
- Use Clean, Healthy Transplants
- Inspect plants for symptoms before planting.
- Ask suppliers about disease screening and nursery sanitation practices.
- Avoid wounding transplants, especially if they’ve been in cold storage.
- Select Resistant or Tolerant Varieties
- Match your variety selection to the diseases present or expected.
- For red stele: ‘Allstar’, ‘Earliglow’, ‘Tribute’, and ‘Tristar’ offer some resistance.
- For Verticillium: ‘Allstar’, ‘DelMarvel’, and ‘Mesabi’ show tolerance.
- Monitor and Respond Quickly
- Scout plantings regularly for uneven growth, stunted plants, or collapse.
- Avoid overwatering and reduce splash with drip irrigation.
- Don’t irrigate with water from surface ponds, which may harbor pathogens.
- Practice Good Sanitation
- Remove and dispose of infected plants.
- Disinfect tools and equipment between fields—especially critical for Neopestalotiopsis.
- Avoid field operations when foliage is wet.
- Use Fungicides Appropriately
- For Phytophthora diseases, apply fungicide preventively or at first sign of symptoms.
- Follow label instructions carefully and rotate chemistries as needed.
- Be cautious with pre-plant dips; research on their effectiveness is mixed.
- Consult the Midwest Fruit Pest Management Guide for the latest recommendations on fungicide efficacy for root and crown rot pathogens of strawberries.
Planning for 2026: Prevention Starts Now
Looking ahead, growers can reduce the risk of future root and crown rot outbreaks with the following steps:
- Select well-drained sites or improve existing drainage systems.
- Use raised beds and drip irrigation to limit soil saturation.
- Choose tolerant cultivars when possible; while no cultivar is fully resistant, some show better field survival.
- Avoid replanting into infected fields without at least one (but three years is recommended!) full season of rotation.
- Consider pre-plant fungicide dips or drenches in known problem fields.
- Manage soil health with rotations, cover crops, and organic matter inputs.
Root and crown rot diseases are complex and often overlooked until plants begin to fail. With multiple pathogens and overlapping symptoms, diagnosis and tailored management are essential for long-term success. While 2025 has brought significant disease pressure in many Wisconsin strawberry fields, a combination of accurate diagnosis, strategic planning, and preventative action can help limit losses this season and build more resilient plantings in the future.
This article was posted in Berries, Disease and tagged crown rot, disease, Leslie Holland, root rot, Strawberries.