Neopestalotiopsis leaf spot and fruit rot is a relatively new disease in Alabama. Since 2022, the disease has been detected in a few strawberry fields, but the damage was minor in the majority of cases. The following are considerations for strawberry producers managing the disease this spring.

2024 Infected Plant Material

Observations of the disease rose dramatically in fall 2024 because Neopestalotiopsis-infected plant material from Canada was shipped to strawberry plug producers and growers in the United States. There was an understanding that growers accepting material from that source should assume the plants would be infected with the disease, even if they looked clean and healthy. There were some growers in Alabama that were able to order disease-free plant material from California and other states. However, other producers in Alabama accepted plants from infested nurseries. Neopestalotiopsis was detected on nine commercial strawberry farms in Alabama during November 2024. Reports suggest that most farms that accepted plants originating from Canada are now battling to keep the disease at bay.

Growers responded with an aggressive fungicide spray program last fall. Coupled with relatively dry weather conditions, producers were able to keep the disease in check going into winter. Luckily, January and February 2025 temperatures were unusually cold for Alabama and well below average, which kept the disease pressure low. However, growers need to be proactive to protect against the disease heading into spring.

Disease Characteristics

As with most fungal diseases, weather plays an important role in determining Neopestalotiopsis intensity. Disease development is favored by prolonged periods of wetness (greater than 24 hours) and mild temperatures (60 to 80 degrees F). The disease is associated with extended periods of rainfall. This can stimulate a field-level epidemic if the pathogen is present. Dry conditions appear to inhibit or reduce spread of the pathogen, and there is minimal spread by wind alone. Obviously, weather conditions this spring will dictate how severe the disease will be in infected fields.

Neopestalotiopsis can produce leaf and petiole lesions, a dark-black fruit rot, and crown rot. Leaf spots can be tan to dark brown, of various sizes, and irregularly distributed on infected leaves (figure 1). Black-fruiting bodies, similar to grains of pepper, become visible within the lesion under moist, humid conditions and are visible with a hand lens (figure 2). Petiole lesions appear as brown-to-black lesions that cause the petiole to die back when girdled (figure 3). Fruit rot begins as dry, light-tan, slightly sunken, and irregularly shaped lesions. The lesions expand and may take over the entire fruit. These large lesions are eventually covered by dark, fungal fruiting bodies (figure 4).

Spring Management Options

Because the disease can be confused with other strawberry diseases, Alabama Cooperative Extension System plant pathologists recommend weekly scouting for the disease and, when necessary, submitting samples to the Auburn University Plant Diagnostic Lab for proper identification. The following is a list of best management options for Neopestalotiopsis this spring:

1. Limit field operations when plants are wet to avoid disease spread.
2. Always work in fields known to be infected with Neopestalotiopsis last.
3. Sanitize your hands, shoes, and clothing when moving out of infected fields.
4. Clean and disinfect equipment after moving out of infected fields.
5. Remove and destroy symptomatic plants, including crowns and roots, during production to reduce inoculum and disease spread.
6. Follow an aggressive fungicide spray program to reduce damage from the disease.

A fungicide program will rely on the fungicide, Thiram, as its anchor. Thiram is a contact fungicide but has been found to be moderately effective against Neopestalotiopsis. The Thiram label allows twelve applications east of the Mississippi River. Consider spraying Thiram every 10 to 14 days, optimally ahead of rain events. In addition, tank mix and/or alternate Thiram with the following fungicides: five applications of Switch and four applications of Rhyme, Tilt, or Inspire (all Demethylation Inhibitor fungicides). Tilt and other generic products containing the active ingredient, propiconazole, have been reported to cause stunting and yield reduction in other states, so use these products cautiously.