What We Know About Neo-P
*Please note photo is of strawberry plants not impacted by Neo-P.
Background
While the fungal genus Neopestalotiopsis (Neo-P) is globally distributed and was first reported in the United States in Florida in 1972, in 2017, a new lineage of Neo-P emerged, coinciding with the major resurgence and spread of the pathogen throughout the southeastern and Pacific regions of the United States. Neo-P outbreaks can be linked to prolonged rainfall, high humidity, and the use of infected nursery transplants.
Neo-P has a wide host range, including agricultural and ornamental crops, and aggressively spreads under favorable environmental conditions, thriving in warm, humid environments. Neo-P affects every part of the plant, including roots, leaves (leaf spot), crowns (crown rot), and fruits (fruit rot). Infected plants often exhibit leaf chlorosis, wilting, stunted growth, and consequent death.
The pathogen can be categorized into aggressive and non-aggressive strains based on symptom severity. Neo-P can act as endophytes (organisms that live in the intercellular spaces of plant tissues), saprophytes (organisms that live on decaying organic matter), or pathogens (organisms causing disease in their host), and is frequently found as part of a disease complex, defined as a disease ultimately determined by multiple genetic and environmental factors. Since its resurgence, reports indicate that Neo-P is commonly an opportunistic fungal genus, meaning it requires a pre-existing condition to infect the plant. Neo-P is commonly found in tandem with other diseases. Often, addressing Neo-P alone will not improve plant health; a correct diagnosis of underlying issues is crucial before intervention. Strawberry plants with confirmed Neo-P can still appear and remain healthy, as long as the inoculum is low and no other disease is present.
Disease Spread
The severity of the outbreak and the speed at which the disease progresses are directly related to environmental conditions. Neo-P thrives between 60–78°F, with increased severity in prolonged wet conditions following rainstorms. Early reports suggest that leaf wetness may play a more pivotal role in infection and development than temperature.
Disease spread in the field and to other fields can be attributed to rain splashing, wind, and human activity. Human activity contributes significantly to disease spread, particularly occurring during periods of extended leaf wetness. Infected hands, clothing, and equipment can be the culprit of disease spread.
Under optimal moisture and temperature conditions, new symptoms are observed as early as five (5) days. Thus, many disease cycles can occur during wet seasons with multiple rain events.
Management
Management is challenging because the pathogen can survive season to season in plant debris and soil and rapidly re-emerge under conducive conditions. Strawberry crowns are the main source of Neo-P that remains in the soil. The best way to ensure a successful crop is to keep inoculum low: remove diseased plant material immediately. Even if infected plants are no longer viable, Neo-P spores are viable.
We recommend a combination of cultural and chemical methods to manage this disease:
Planting Pathogen-Free Plants: Clean plants are crucial for success. If ordering plants from multiple nurseries, consider keeping each nursery’s plants isolated from the others to limit spread if Neo-P affects any of them.
Growing Techniques: Growing methods can strongly influence Neo-P in fields. Mitigating abiotic stress factors, such as drought, extreme temperatures, mechanical damage, nutrient imbalances, and salinity, can reduce your risk of infection. Other recommended cultural practices include maintaining proper plant spacing to maximize airflow and leaf drying, and removing nearby host plants before planting.
Sites with poor drainage and/or standing water significantly increase the risk of Neo-P and Neo-P spread; ensure fields have consistent drainage.
Watering: To limit disease spread by wind and rain, we recommend drip irrigation. It’s important to have a comprehensive understanding of your water and to determine how clean it is of pathogens, and if disinfection is necessary. Testing your water frequently provides insights into its composition (nutrition, hardness, pH, etc.) and allows you to tailor a nutrition program based on the results.
Crop Rotation: Reduce inoculum build-up by crop rotating every three to four (3–4) years. It may take up to three (3) years for Neo-P field levels to decrease. Ensure you are rotating with a non-host of Neo-P.
Sterilization and Sanitation: Neo-P spores can be recovered months after contact. Clean, then disinfect everything that could come into contact with spores. For sanitizing equipment surfaces, such as tools, benches, irrigation systems, and trays, quaternary ammonium compounds are effective. It is recommended to sterilize row covers with a steam treatment before use.
Human activity contributes significantly to disease spread, particularly during wet conditions; avoid handling plants when wet. Other ways to improve sanitation and reduce inoculum include using foot baths, disposable gloves, and booties between each variety in the field.
If you have a field infected by Neo-P, we strongly encourage you to work in the clean fields first to minimize the spread of spores to non-infested fields.
Scouting: We recommend visually inspecting plants frequently and looking for symptoms. If you suspect Neo-P in your fields, talk to disease specialists, collect a sufficient sample size, and use a trusted laboratory to test your planting material for infection.
Nourse Fams Grows Differently to Mitigate the Risks of Neo-P
We understand that the first step in winning the fight with Neo-P is ensuring you start with a clean planting. Our quality control begins at our on-site lab, where we propagate mother plants from tissue culture. This process allows us to regularly test our planting stock and ensure only clean plants are entering our greenhouses and fields.
Since the outbreak of Neo-P, we’ve expanded our propagation systems to shield our plants from weather-related stress and reduce disease pressure. We grow our tips in a high-tech glasshouse, which allows us to keep the mother plants and the runner tips clean. With this system, we’re able to provide customers with uniform tips, which leads to uniform watering and fewer fungal problems. We have adopted a GeGe rail tray system under tunnels to reduce the risk of soil contact and water splashing, protecting the plants from disease. We’ve found that this system significantly improves airflow around the plants, encouraging better root development.
During propagation, crew members regularly scout for disease, and leaf tissue samples are sent to the University of Florida for monitoring of fungal diseases such as Neo-P.
To us, quality is non-negotiable. We’ve enhanced our sanitation practices to ensure we’re doing everything possible to mitigate the risk of disease. These methods include cleaning and sanitizing production areas between crops, setting up vehicle, hand, and foot sanitizing areas at the entrance and exit of production areas using quaternary ammonium disinfectants, reducing leaf wetness by controlling humidity in production areas, and irrigating on sunny days. Further, we add a safe surfactant, such as H2Pro, to the irrigation water to speed leaf drying.
We’ve found success using the following for Neo-P and other fungal control methods:
- Captan (Group MO4): 3 quarts/acre
- Thiram (Group MO3): 2.6 quarts/acre
- Quadris Top (Groups 3 and 11): 14 fluid ounces/acre
- Chlorothalonil (Group MO5): 1.5 pints/acre
- Switch or Palladium (Groups 9 and 12): 14 ounces/acre
Understanding timing, quantities, and spray history is critical for successful fungal control.
Contact your local extension office for specific recommendations tailored to your operation.
Collective Action to Face Challenges
Nourse Farms is committed to working with industry leaders, research facilities, and growers to understand the challenges posed by Neo-P and to take collaborative action. We recognize that the industry is stronger when we work and grow together. We are dedicated to adopting the best mitigation practices as they arise to ensure we continue to provide the best plants possible.
This article is from our February Edition of Growing Together.
