Neopestalotiopsis fruit rot and leaf spot, caused by Neopestalotiopsis species, first caused damage in Florida strawberry fields in 2019 and 2020. Since then, the disease has spread to most southeastern states and is already a major concern for the upcoming 2024-2025 strawberry season. Strawberry producers are on alert, with some nurseries already sounding alarms about Neopestalotiopsis. The issue is particularly concerning for nurseries and producers that rely on strawberry tips from Prince Edward Island. One major nursery, which supplies these tips, issued a warning letter on August 19, 2024. Other nurseries have followed suit, canceling orders, refunding deposits, or advising producers to take plants at their own risk, with no reimbursements for diseased or infected plants.
The high disease levels observed in nurseries, coupled with these liability limitations, are likely to impact the supply of tips and plug plants for many strawberry producers. This year marks the first time a direct and immediate link to Prince Edward Island has been identified, raising significant concerns for the industry.
During the nursery phase, some plug plant producers may still attempt to grow plants from infected tips. While some of these plants might appear healthy, producers who choose to receive plug plants from nurseries known to have Neopestalotiopsis-infected plants must cull any unhealthy plants upon arrival. Though this may seem wasteful, it is crucial to prevent the spread of Neopestalotiopsis, as the level of initial inoculum directly affects the disease severity later in the season. Unless plants are sourced from regions without Neopestalotiopsis issues, such as California, all producers should assume that their plants carry the pathogen, even if they appear clean and healthy. Therefore, implementing an aggressive spray program that targets Neopestalotiopsis and other strawberry diseases is essential from the time of transplanting.
The disease is strongly associated with long periods of rainfall, so a dry season may help limit its spread. However, rain is common during strawberry production, and if the Neopestalotiopsis pathogen is present, it can trigger a field epidemic. The following best management practices are recommended: (1) source disease-free transplants; (2) avoid planting highly susceptible varieties (as no resistant varieties are currently available); (3) discard unhealthy plants and destroy those not planted; (4) limit field activities, such as harvesting and spraying, when plants are wet; (5) sanitize hands, shoes, and clothing when leaving infected fields; (6) clean and disinfect equipment after working in infected fields; (7) remove and destroy symptomatic plants, including crowns and roots, during production to reduce inoculum and prevent disease spread; and (8) incorporate effective fungicides into an aggressive spray program. After harvest, thoroughly harrow fields to break up remaining strawberry crowns, and consider rotating crops for two years to allow survival structures to break down. Pre-plant fumigation is also recommended to reduce inoculum levels, though it won’t completely control the disease year-to-year. Using both Vapam and PicClor 60 can enhance fumigation effectiveness against fungal pathogens.
Given the timing, some options are now limited. Producers should bring in the best plants available. Since finding clean plants may be difficult, producers need to consider their level of risk tolerance, with some opting to skip production this year. For those who continue, Thiram will be the cornerstone of the spray program. This contact fungicide is effective against Neopestalotiopsis and Botrytis. However, the EPA may soon remove Thiram from the market, so stay informed about potential regulation changes. Currently, some Thiram labels allow up to 12 applications east of the Mississippi River but limit applications to five west of the Mississippi. Producers should spray the maximum number of Thiram applications allowed by the label, every 10-14 days, ideally before rain events. Begin spraying soon after transplanting and continue in the spring, pausing only during extreme winter cold. Additionally, tank mix or alternate Thiram with other fungicides like Switch (five applications at 11 oz/acre) and Rhyme, Tilt, or Inspire (DMI fungicides, limited to four applications). Note that Tilt and similar generics containing propiconazole should be limited to three or fewer applications, as they have caused stunting and yield reduction in Florida. East of the Mississippi, producers can apply Thiram 12 times, with nine applications including a mix of Thiram and a systemic fungicide like Switch or a DMI fungicide. These combinations should provide the best control for Neopestalotiopsis while also managing Botrytis and powdery mildew.
Despite these challenges, there is hope for a successful strawberry production year. Your local county agent is also a valuable resource for any questions or issues related to strawberry production.