This article was initially run in the Wisconsin Fruit Newsletter in April 2021. After a particularly hot, humid, and rainy month of May in Wisconsin, I wanted to put this disease back on our radars as we head into June. Note: there have been no additional reports of this disease in Wisconsin since 2021. However, the warm and wet conditions last month are favorable to the development of disease. A few things to keep in mind about this disease:
- Many cases in other states where Neopestalotiopsis has been reported have been associated with recently transplanted strawberry plants.
- Symptoms can manifest on leaves, crowns, roots, and fruits. Early symptoms include tan lesions on the leaves. However, these symptoms can be easily confused with other foliar diseases, so accurate diagnosis is necessary (read more below).
- If you suspect this disease in your field, please submit a sample to the UW Plant Disease Diagnostic Clinic for diagnosis.
What is Neopestalotiopsis leaf spot and fruit rot?
A fungal disease was recently identified in strawberry fields in North America, specifically in several states including Florida, New Jersey, North Carolina, Georgia, and in Ontario, Canada. The disease was recently detected in Florida in 2017 with subsequent outbreaks in 2018 and 2019. Most cultivars grown in Florida appear to be susceptible to infection by the pathogen (Neopestalotiopsis sp.), and severe crop losses have been reported in many fields.
What are the symptoms of Neopestalotiopsis leaf spot and fruit rot?
Symptoms of the disease can appear on most tissue types. On leaves, small spots with light brown centers and dark borders appear first. As the infection advances, these spots expand and merge forming irregular-shaped, necrotic lesions. Stunting and dieback of the entire plant may occur. Fruit infections begin as small, tan lesions that eventually turn orange before they are covered in black fungal spores. Infections of the crown may also develop, resulting in orange-brown discoloration and crown rot. Crown infections cause poor establishment following transplant.
Symptoms of Neopestalotiopsis leaf spot and fruit rot are very similar to other strawberry diseases, making field diagnosis difficult. For instance, leaf spot symptoms are also associated with Leaf Scorch or Common Leaf Spot diseases. Fruit symptoms of Neopestalotiopsis are very similar to Anthracnose infections, the major difference is the development of black spores in the fruit lesions; the fungus that causes Anthracnose has salmon-colored spores. Crown rot and dieback symptoms of Neopestalotiopsis can be easily confused Phytophthora or Anthracnose crown rot infections.
How does Neopestalotiopsis spread?
Neopestalotiopsis species are often considered a secondary issue. Traditionally, the fungus is thought to be a weak pathogen that infects stressed plants. However, new isolates of this pathogen in Florida are more aggressive and the severity of infections is much higher. Additionally, further research on the Florida isolates demonstrates that this new species of Neopestalotiopsis is producing spores at a higher rate, likely contributing to increased spread. The pathogen thrives in warm and humid conditions, and temperatures above 50°F are favored for growth with optimal temperatures around 77°F. High humidity and rain events are very conducive for pathogen spread. Movement of the pathogen on plant material has also been observed.
Has Neopestalotiopsis been reported in Wisconsin strawberries?
Yes, the fungal pathogen Neopestalotiopsis has been identified in one location in Wisconsin in 2021. That disease alert can be found here.
How do I manage Neopestalotiopsis leaf spot and fruit rot?
- No genetically resistant varieties have been identified.
- Start with clean planting material. Inspect plants carefully from the nursery for symptoms of the disease, and do not plant symptomatic strawberries.
- Minimize working with the plants when they are wet to avoid spreading the fungus.
- Trials in Florida indicate that the fungicidesSwitch and Thiram reduced disease incidence.
NOTE: Mention of a fungicide product is not a recommendation or endorsement of a product.
What do I do if I suspect Neopestalotiopsis in my strawberries?
If you suspect your strawberry plants may be infected, submit samples for diagnosis to the UW Plant Disease Diagnostics Clinic. Since symptoms of this disease can be easily confused with other strawberry diseases it is recommended that you submit a physical plant sample for diagnosis, as pictures may not be sufficient to identify a new disease.
For more information on this emerging disease concern, including photos of the symptoms, see the fact sheet from Dr. Natalia Peres’ Lab at the University of Florida.This article was posted in Disease and tagged disease, Leslie Holland, Neopestalotiopsis, Strawberries.