Potato Early Blight
Potato early blight is a foliar fungal disease caused primarily by Alternaria solani. Initial infection frequently appears on older lower leaves and develops in a gradual upward progression within the canopy. Lesion often enlarge and develop a characteristics concentric rings surrounded by chlorotic halos. As disease progresses, lesion may coalesce that could lead to extensive blighting, premature defoliation and reduction of photosynthetic capacity. Infected tubers may show dark, circular to irregular in shape and sunken lesions often surrounded by a raise margins. It can severely decrease the leaf surface area which in turn reduces tuber yield potential. Tuber infection and subsequent decay in storage affect the quality of the seed, marketability, and processing.
Alternating wet and dry periods and high relative humidity are the most favorable conditions for spore formation and dispersal. Prolonged leaf wetness from dew, rain and irrigation promotes conidial germination and infection. Spore dispersal occurs in a diurnal pattern, and more spores are dispersed during the day as foliage dries. Spores can also move long distances through air currents. Moreover, plants under stress from nutrient deficiencies, drought and other diseases are more susceptible to the disease infection.
Potato Brown Spot
Potato brown spot is caused by Alternaria alternata. The disease is often confused with early blight, however, brown spot is characterized by distinct morphological symptoms, such as small, dark brown necrotic spots measuring 10 mm in diameter. Small spots may coalesce to form larger necrotic areas, which lack a prominent concentric ring of early blight symptoms. Severely affected foliage may dry up and senesce prematurely. Consequently, the most detrimental symptom is a black pit on tubers, especially those damaged during harvest. Symptoms appear as deep, black, and sunken lesions which may develop during storage.
This pathogen is considered a weak pathogen, attacks plants weakened by other plant pathogens, nutrient deficiencies, stress, and senescence. Infection occurs when spores dispersed primarily by wind, land on susceptible potato foliage at any growth stage of the plant. Disease development is favored by warm temperatures, typically over 18 °C, coupled with long dew periods (Droby et al., 1984). Infected leaves are the primary source of infection after harvest, and the pathogen survives on infected debris in the soil and in the tubers as well.
Additional Resources
Potato Late Blight Disease Resources
- Late blight: UF IFAS
- Potato late blight: North Carolina State University
- Potato late blight: North Dakota State University
- Potato late blight: University of California
Early Blight of Potato Resources
- Early Blight of Potato: The American Phytopathological Society (APS)
- Early blight: University of California
- Early blight and potato late blight: University of Connecticut
- Early blight in potato: University of Minnesota
Brown Leafspot of Potato Resources
March 17, 2025
Spore Report Alert System 
🔴 Red: Spores detected, indicating a potential disease risk. 
🟡 Yellow: Spores detected in 1-2 spore traps, indicating close monitoring.  
🟢 Green: No spores detected, indicating no immediate concern.
Early blight/brown spots fungal spores associated with Alternaria solani and Alternaria alternata (A) were detected in both passive and active spore traps strategically placed in potato commercial fields at St. Johns and Putnam Counties, indicating potential disease risks under favorable conditions. However, late blight spores, usually associated with Phytophthora sp. (P), were not detected across all traps, suggesting no immediate risk for late blight at the time of sampling.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to stay vigilant and refine their management strategies, using spore reports as a guide tool, alongside prevailing environmental conditions, to mitigate potential risks.
Environmental Conditions Favoring Disease Development
Early Blight (Alternaria solani)
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.
Brown Spot (Alternaria alternata)
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.
Late Blight (Phytophthora infestans)
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly.
Spore Report Alert System 
🔴 Red: Spores detected, indicating a potential disease risk. 
🟡 Yellow: Spores detected in 1-2 spore traps, indicating close monitoring.  
🟢 Green: No spores detected, indicating no immediate concern.
Alternaria early blight and brown spot fungal spores, associated with Alternaria solani and Alternaria alternata (A), respectively, were detected in all four passive and active spore traps placed strategically in commercial potato fields and experimental station in St. Johns County. Meanwhile, spores of these diseases were detected in three spore trap samplers at Putnam County. This widespread detection suggests a potential risk of disease development under favorable environmental conditions.  
Additionally, Phytophthora sp. (P), usually associated with potato late blight in potato fields, was detected at Location No. 2 in St. Johns County from two spore traps and Location No. 3 in Putnam County from one active spore trap. The detection highlights close monitoring/ moderate risk of late blight, particularly if weather conditions continue to favor pathogen activity.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to stay vigilant and refine their management strategies, using spore reports as a guide tool alongside prevailing environmental conditions to mitigate potential risks. 
Environmental Conditions Favoring Disease Development
Early Blight (Alternaria solani)
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.
Brown Spot (Alternaria alternata)
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.
Late Blight (Phytophthora infestans)
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly.
Spore Report Alert System
🔴 Red: Spores detected, indicating a potential disease risk.
🟡 Yellow: Spores detected in 1-2 spore traps, indicating close monitoring.
🟢 Green: No spores detected, indicating no immediate concern.
|
Pathogen |
Disease |
Detection Summary* |
|
Alternaria solani Alternaria Alternata |
Early blight Brown Spot |
Detected in all traps – St. Johns Co. Detected in 3 traps – Putnam Co. |
|
Phytophthora infestans |
Late Blight |
Detected in 2 traps – St. Johns Co. Detected in 1 trap – Putnam Co. |
*Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, and local weather to guide your actions.
Alternaria early blight and brown spot fungal spores, associated with Alternaria solani and Alternaria alternata (A), respectively, were detected in all four passive and active spore traps placed strategically in commercial potato fields and experimental station in St. Johns County. Meanwhile, spores of these diseases were detected in three spore trap samplers at Putnam County. This widespread detection suggests a potential risk of disease development under favorable environmental conditions.
Additionally, Phytophthora sp. (P), usually associated with potato late blight in potato fields, was detected at Location No. 2 in St. Johns County from two spore traps and Location No. 3 in Putnam County from one active spore trap. The detection highlights close monitoring/ moderate risk of late blight, particularly if weather conditions continue to favor pathogen activity.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to stay vigilant and refine their management strategies, using spore reports as a guide tool alongside prevailing environmental conditions to mitigate potential risks.
Environmental Conditions Favoring Disease Development
Early Blight (Alternaria solani)
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.
Brown Spot (Alternaria alternata)
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.
Late Blight (Phytophthora infestans)
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly.
Spore Report Alert System 
🔴 Red: Spores detected, indicating a potential disease risk. 
🟡 Yellow: Spores detected in 1-2 spore traps, indicating close monitoring.  
🟢 Green: No spores detected, indicating no immediate concern.
|
Pathogen |
Disease |
Detection Summary* |
|
Alternaria solani Alternaria alternata |
Early blight Brown Spot |
Detected in all traps – St. Johns Co. Detected in 3 traps – Putnam Co. |
|
Phytophthora infestans |
Late Blight |
Not detected |
 *Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, and local weather to guide your actions.
Alternaria early blight and brown spot fungal spores, associated with Alternaria solani and Alternaria alternata (A), respectively, were detected in all four passive and active spore traps placed strategically in commercial potato fields and experimental station in St. Johns County. Meanwhile, spores of these diseases were detected in three spore trap samplers at Putnam County. This widespread detection suggests a potential risk of disease development under favorable environmental conditions.  
Additionally, Phytophthora sp. (P), usually associated with late blight in potato fields, was not detected in both Counties, specifying no immediate risk at the time of sampling.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to stay vigilant and refine their management strategies, using spore reports as a guide tool alongside prevailing environmental conditions to mitigate potential risks. 
Environmental Conditions Favoring Disease Development
Early Blight (Alternaria solani)
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.
Brown Spot (Alternaria alternata)
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.
Late Blight (Phytophthora infestans)
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly.
Spore Report Alert System 
🔴 Red: Spores detected, indicating a potential disease risk. 
🟡 Yellow: Spores detected in 1-2 spore traps, indicating close monitoring.  
🟢 Green: No spores detected, indicating no immediate concern.
|
Pathogen |
Disease |
Detection Summary* |
|
Alternaria solani Alternaria alternata |
Early blight Brown Spot |
Detected in all traps – St. Johns Co. Detected in all traps – Putnam Co. |
|
Phytophthora sp. |
Late Blight |
Detected in one trap- St. Johns and Putnam Co. |
 *Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, and local weather to guide your actions.
Alternaria early blight and brown spot fungal spores, associated with Alternaria solani and Alternaria alternata (A), respectively, were detected in all four passive and active spore traps placed strategically in commercial potato fields and experimental station in St. Johns County. Meanwhile, spores of these diseases were also detected in all spore traps at Putnam County. This widespread detection suggests a potential risk of disease development under favorable environmental conditions.  
Additionally, Phytophthora sp. (P), usually associated with potato late blight in potato fields, was detected in all sampling locations from one active spore trap. The detection highlights close monitoring/ moderate risk of late blight, particularly if weather conditions continue to favor pathogen activity.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to stay vigilant and refine their management strategies, using spore reports as a guide tool alongside prevailing environmental conditions to mitigate potential risks. 
Environmental Conditions Favoring Disease Development
Early Blight (Alternaria solani)
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.
Brown Spot (Alternaria alternata)
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.
Late Blight (Phytophthora infestans)
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly.
Spore Report Alert System 
🔴 Red: Spores detected, indicating a potential disease risk. 
🟡 Yellow: Spores detected in 1-2 spore traps, indicating close monitoring.  
🟢 Green: No spores detected, indicating no immediate concern.
|
Pathogen |
Disease |
Detection Summary* |
|
Alternaria solani Alternaria alternata |
Early blight Brown Spot |
Detected in 3 traps – St. Johns Co. Detected in all traps – Putnam Co. |
|
Phytophthora sp. |
Late Blight |
Detected in one trap- St. Johns and Putnam Co. |
Alternaria early blight and brown spot fungal spores, associated with Alternaria solani and Alternaria alternata (A), respectively, were detected in three spore traps spore traps placed strategically in commercial potato fields and experimental station in St. Johns County. Meanwhile, spores of these diseases were also detected in all spore traps at Putnam County. This widespread detection suggests a potential risk of disease development under favorable environmental conditions.  
Additionally, Phytophthora sp. (P), usually associated with potato late blight in potato fields, was detected in St. Johns and Putnam Counties from one active spore trap. The detection highlights close monitoring/ moderate risk of late blight, particularly if weather conditions favor pathogen activity.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to stay vigilant and refine their management strategies, using spore reports as a guide tool alongside prevailing environmental conditions to mitigate potential risks. 
Environmental Conditions Favoring Disease Development
Early Blight (Alternaria solani)
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.
Brown Spot (Alternaria alternata)
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.
Late Blight (Phytophthora infestans)
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly.
POTATO SPORE REPORT
|
Pathogen |
Disease |
Visual Risk Alert/ Detection Summary |
|
|
Alternaria solani, |
Early blight, |
🔴
|
Detected in all traps at St Johns and Putnam Counties
|
|
Phytophthora infestans |
Late blight |
🟢 |
Not detected in all traps at St Johns and Putnam Counties
|
Spore Report Alert System  
🔴 Spores detected, indicating a potential disease risk, close monitor the field.
🟢  No spores detected, indicating no immediate concern.
Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, local weather, and fungicide resistance data to guide your actions.
Early blight and brown spot fungal spores were detected in both passive and active spore traps, including rotorods, Yroot samplers, and volumetric cyclone samplers strategically placed in potato fields at the UF-IFAS Hastings Agricultural Education Center (HAEC) as well as in commercial fields in St. Johns and Putnam Counties. These pathogens were also detected using a Burkard volumetric spore trap at the UF-IFAS HAEC station at . The presence of airborne spores indicates a potential risk for disease development when environmental conditions become favorable. In contrast, spores associated with late blight were not detected across all traps during the sampling period, suggesting no immediate risk of late blight at this time.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to remain vigilant and adjust their management strategies, accordingly, using spore monitoring reports together with current weather conditions to help reduce potential disease risks.
In addition, monitoring of airborne Alternaria spores using a 7-day volumetric Burkard spore trap showed that spore concentrations were generally low during nighttime hours between 6:00 PM to 5:00 AM but increased significantly in the early morning. The highest spore levels were consistently detected between 6:00 AM and 12:00 noon, after which concentrations gradually declined toward the afternoon between 1:00 PM to 5:00 PM. These results indicate that the morning period represents the peak time for Alternaria spore dispersal.
Based on these observations, growers are encouraged to consider early morning fungicide applications (approximately 7:00–10:00 AM) when spore release is high and temperatures remain moderate, which may help improve spray coverage before foliage dries rapidly later in the day.
Critical Fungicide Management Notice (New Integration)
A G143A mutation, conferring complete resistance to QoI fungicides, has been detected in spore trap samples collected from potato fields in St. Johns and Putnam Counties from March to April 2025. QoI fungicides are recommended to be applied only in mixtures with partners that can contribute to effective control. Cross-resistance between all members of the code 11 fungicides is known. Moreover, common SDHIs mutations such as H277R, H278R and H133R were not detected in the analyzed samples. Review the Fungicide Application Guide for full details on resistance management: FRAC: QoI Fungicides and FRAC: SDHI Fungicides
Environmental Conditions Favoring Disease Development 
Early Blight (Alternaria solani) 
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.  
Brown Spot (Alternaria alternata) 
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.  
Late Blight (Phytophthora infestans) 
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to 25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly. 
POTATO SPORE REPORT
|
Pathogen |
Disease |
Visual Risk Alert/ Detection Summary |
|
|
Alternaria solani, |
Early blight, |
🔴
|
Detected in all traps at St Johns and Putnam Counties
|
|
Phytophthora infestans |
Late blight |
🟢 |
Not detected in all traps at St Johns and Putnam Counties
|
Spore Report Alert System  
🔴 Spores detected, indicating a potential disease risk, close monitor the field.
🟢  No spores detected, indicating no immediate concern.
Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, local weather, and fungicide resistance data to guide your actions.
Early blight and brown spot fungal spores were detected in both passive and active spore traps, including rotorods, Yroot samplers, and volumetric cyclone samplers strategically placed in potato fields at the UF-IFAS Hastings Agricultural Education Center (HAEC) as well as in commercial fields in St. Johns and Putnam Counties. These pathogens were also detected using a Burkard volumetric spore trap at the UF-IFAS HAEC station. The presence of airborne spores indicates a potential risk for disease development when environmental conditions become favorable. In contrast, spores associated with late blight were not detected across all traps during the sampling period, suggesting no immediate risk of late blight at this time.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to remain vigilant and adjust their management strategies, accordingly, using spore monitoring reports together with current weather conditions to help reduce potential disease risks.
In addition, monitoring of airborne Alternaria spores using a 7-day volumetric Burkard spore trap showed that spore concentrations were generally low during nighttime hours between 6:00 PM to 5:00 AM but increased significantly in the early morning. The highest spore levels were consistently detected between 6:00 AM and 12:00 noon, after which concentrations gradually declined toward the afternoon between 1:00 PM to 5:00 PM. These results indicate that the morning period represents the peak time for Alternaria spore dispersal.
Based on these observations, growers are encouraged to consider early morning fungicide applications (approximately 7:00–10:00 AM) when spore release is high and temperatures remain moderate, which may help improve spray coverage before foliage dries rapidly later in the day.
Environmental Conditions Favoring Disease Development 
Early Blight (Alternaria solani) 
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.  
Brown Spot (Alternaria alternata) 
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.  
Late Blight (Phytophthora infestans) 
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to 25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly. 
POTATO SPORE REPORT
|
Pathogen |
Disease |
Visual Risk Alert/ Detection Summary |
|
|
Alternaria solani, |
Early blight, |
🔴
|
Detected in all traps at St Johns and Putnam Counties
|
|
Phytophthora infestans |
Late blight |
🟢 |
Not detected in all traps at St Johns and Putnam Counties
|
Spore Report Alert System  
🔴 Spores detected, indicating a potential disease risk, close monitor the field.
🟢  No spores detected, indicating no immediate concern.
Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, local weather, and fungicide resistance data to guide your actions.
Early blight and brown spot fungal spores were detected in both passive and active spore traps, including rotorods, Yroot samplers, and volumetric cyclone samplers strategically placed in potato fields at the UF-IFAS Hastings Agricultural Education Center (HAEC) as well as in commercial fields in St. Johns and Putnam Counties. These pathogens were also detected using a Burkard volumetric spore trap at the UF-IFAS HAEC station. The presence of airborne spores indicates a potential risk for disease development when environmental conditions become favorable. In contrast, spores associated with late blight were not detected across all traps during the sampling period, suggesting no immediate risk of late blight at this time.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to remain vigilant and adjust their management strategies, accordingly, using spore monitoring reports together with current weather conditions to help reduce potential disease risks.
In addition, monitoring of airborne Alternaria spores using a 7-day volumetric Burkard spore trap showed that spore concentrations were generally low during nighttime hours between 6:00 PM to 5:00 AM but increased significantly in the early morning. The highest spore levels were consistently detected between 6:00 AM and 12:00 noon, after which concentrations gradually declined toward the afternoon between 1:00 PM to 5:00 PM. These results indicate that the morning period represents the peak time for Alternaria spore dispersal.
Based on these observations, growers are encouraged to consider early morning fungicide applications (approximately 7:00–10:00 AM) when spore release is high and temperatures remain moderate, which may help improve spray coverage before foliage dries rapidly later in the day.
Environmental Conditions Favoring Disease Development 
Early Blight (Alternaria solani) 
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.  
Brown Spot (Alternaria alternata) 
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.  
Late Blight (Phytophthora infestans) 
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to 25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly. 
POTATO SPORE REPORT
|
Pathogen |
Disease |
Visual Risk Alert/ Detection Summary |
|
|
Alternaria solani, |
Early blight, |
🔴
|
Detected in all traps at St Johns and Putnam Counties
|
|
Phytophthora infestans |
Late blight |
🟢 |
Not detected in all traps at St Johns and Putnam Counties
|
Spore Report Alert System  
🔴 Spores detected, indicating a potential disease risk, close monitor the field.
🟢  No spores detected, indicating no immediate concern.
Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, local weather, and fungicide resistance data to guide your actions.
Early blight and brown spot fungal spores were detected in both passive and active spore traps, including rotorods, Yroot samplers, and volumetric cyclone samplers strategically placed in potato fields at the UF-IFAS Hastings Agricultural Education Center (HAEC) as well as in commercial fields in St. Johns and Putnam Counties. These pathogens were also detected using a Burkard volumetric spore trap at the UF-IFAS HAEC station. The presence of airborne spores indicates a potential risk for disease development when environmental conditions become favorable. In contrast, spores associated with late blight were not detected across all traps during the sampling period, suggesting no immediate risk of late blight at this time.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to remain vigilant and adjust their management strategies, accordingly, using spore monitoring reports together with current weather conditions to help reduce potential disease risks.
In addition, monitoring of airborne Alternaria spores using a 7-day volumetric Burkard spore trap showed that spore concentrations were generally low during nighttime hours between 6:00 PM to 5:00 AM but increased significantly in the early morning. The highest spore levels were consistently detected between 6:00 AM and 12:00 noon, after which concentrations gradually declined toward the afternoon between 1:00 PM to 5:00 PM. These results indicate that the morning period represents the peak time for Alternaria spore dispersal.
Based on these observations, growers are encouraged to consider early morning fungicide applications (approximately 7:00–10:00 AM) when spore release is high and temperatures remain moderate, which may help improve spray coverage before foliage dries rapidly later in the day.
Environmental Conditions Favoring Disease Development 
Early Blight (Alternaria solani) 
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.  
Brown Spot (Alternaria alternata) 
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.  
Late Blight (Phytophthora infestans) 
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to 25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly. 
Critical Fungicide Management Notice (New Integration)
Mixtures of QoI-sensitive and QoI-resistant Alternaria populations were detected in aerial spore samples. The G143A mutation, which confers complete resistance to QoI (FRAC Group 11) fungicides, was identified in spore trap samples collected from potato fields in St. Johns and Putnam Counties during March 2026, as well as in samples collected during the March–April 2025 sampling period. QoI fungicides azoxystrobin-based products (e.g., Quadris, Satori, and Equation), fenamidone (Reason 500 SC), and pyraclostrobin (Cabrio EG and Headline 2.09 F). Due to the presence of resistant populations and the known cross-resistance among all FRAC Group 11 fungicides, these products are recommended to be applied in mixtures with fungicides of different modes of action to maintain effective disease control. While QoI fungicides may still provide some level of control, their use as standalone applications can increase the frequency of resistant populations, making mixture strategies essential. Moreover, common SDHI resistance mutations (H277R, H278R, and H133R) were not detected in the analyzed samples. Review the Fungicide Application Guide for full details on resistance management: FRAC Group 11: QoI Fungicides and FRAC Group 3: SDHI Fungicides. In addition, consult the Vegetable Production Handbook in Florida for recommended fungicides mixtures and application programs.
POTATO SPORE REPORT
|
Pathogen |
Disease |
Visual Risk Alert/ Detection Summary |
|
|
Alternaria solani, |
Early blight, |
🔴
|
Detected in all traps at St Johns and Putnam Counties
|
|
Phytophthora infestans |
Late blight |
🟢 |
Not detected in all traps at St Johns and Putnam Counties
|
Spore Report Alert System  
🔴 Spores detected, indicating a potential disease risk, close monitor the field.
🟢  No spores detected, indicating no immediate concern.
Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, local weather, and fungicide resistance data to guide your actions.
Early blight and brown spot fungal spores were detected in both passive and active spore traps, including rotorods, Yroot samplers, and volumetric cyclone samplers strategically placed in potato fields at the UF-IFAS Hastings Agricultural Education Center (HAEC) as well as in commercial fields in St. Johns and Putnam Counties. These pathogens were also detected using a Burkard volumetric spore trap at the UF-IFAS HAEC station. The presence of airborne spores indicates a potential risk for disease development when environmental conditions become favorable. In contrast, spores associated with late blight were not detected across all traps during the sampling period, suggesting no immediate risk of late blight at this time.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to remain vigilant and adjust their management strategies, accordingly, using spore monitoring reports together with current weather conditions to help reduce potential disease risks.
In addition, monitoring of airborne Alternaria spores using a 7-day volumetric Burkard spore trap showed that spore concentrations were generally low during nighttime hours between 6:00 PM to 5:00 AM but increased significantly in the early morning. The highest spore levels were consistently detected between 6:00 AM and 12:00 noon, after which concentrations gradually declined toward the afternoon between 1:00 PM to 5:00 PM. These results indicate that the morning period represents the peak time for Alternaria spore dispersal.
Based on these observations, growers are encouraged to consider early morning fungicide applications (approximately 7:00–10:00 AM) when spore release is high and temperatures remain moderate, which may help improve spray coverage before foliage dries rapidly later in the day.
Environmental Conditions Favoring Disease Development 
Early Blight (Alternaria solani) 
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.  
Brown Spot (Alternaria alternata) 
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.  
Late Blight (Phytophthora infestans) 
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to 25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly. 
Critical Fungicide Management Notice (New Integration)
Mixtures of QoI-sensitive and QoI-resistant Alternaria populations were detected in aerial spore samples. The G143A mutation, which confers complete resistance to QoI (FRAC Group 11) fungicides, was identified in spore trap samples collected from potato fields in St. Johns and Putnam Counties during March 2026, as well as in samples collected during the March–April 2025 sampling period. QoI fungicides azoxystrobin-based products (e.g., Quadris, Satori, and Equation), fenamidone (Reason 500 SC), and pyraclostrobin (Cabrio EG and Headline 2.09 F). Due to the presence of resistant populations and the known cross-resistance among all FRAC Group 11 fungicides, these products are recommended to be applied in mixtures with fungicides of different modes of action to maintain effective disease control. While QoI fungicides may still provide some level of control, their use as standalone applications can increase the frequency of resistant populations, making mixture strategies essential. Moreover, common SDHI resistance mutations (H277R, H278R, and H133R) were not detected in the analyzed samples. Review the Fungicide Application Guide for full details on resistance management: FRAC Group 11: QoI Fungicides and FRAC Group 3: SDHI Fungicides. In addition, consult the Vegetable Production Handbook in Florida for recommended fungicides mixtures and application programs.
POTATO SPORE REPORT
|
Pathogen |
Disease |
Visual Risk Alert/ Detection Summary |
|
|
Alternaria solani, |
Early blight, |
🔴
|
Detected in all traps at St Johns and Putnam Counties
|
|
Phytophthora infestans |
Late blight |
🟢 |
Not detected in all traps at St Johns and Putnam Counties
|
Spore Report Alert System  
🔴 Spores detected, indicating a potential disease risk, close monitor the field.
🟢  No spores detected, indicating no immediate concern.
Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, local weather, and fungicide resistance data to guide your actions.
Early blight and brown spot fungal spores were detected in both passive and active spore traps, including rotorods, Yroot samplers, and volumetric cyclone samplers strategically placed in potato fields at the UF-IFAS Hastings Agricultural Education Center (HAEC) as well as in commercial fields in St. Johns and Putnam Counties. These pathogens were also detected using a Burkard volumetric spore trap at the UF-IFAS HAEC station. The presence of airborne spores indicates a potential risk for disease development when environmental conditions become favorable. In contrast, spores associated with late blight were not detected across all traps during the sampling period, suggesting no immediate risk of late blight at this time.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to remain vigilant and adjust their management strategies, accordingly, using spore monitoring reports together with current weather conditions to help reduce potential disease risks.
In addition, monitoring of airborne Alternaria spores using a 7-day volumetric Burkard spore trap showed that spore concentrations were generally low during nighttime hours between 6:00 PM to 5:00 AM but increased significantly in the early morning. The highest spore levels were consistently detected between 6:00 AM and 12:00 noon, after which concentrations gradually declined toward the afternoon between 1:00 PM to 5:00 PM. These results indicate that the morning period represents the peak time for Alternaria spore dispersal.
Based on these observations, growers are encouraged to consider early morning fungicide applications (approximately 7:00–10:00 AM) when spore release is high and temperatures remain moderate, which may help improve spray coverage before foliage dries rapidly later in the day.
Environmental Conditions Favoring Disease Development 
Early Blight (Alternaria solani) 
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.  
Brown Spot (Alternaria alternata) 
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.  
Late Blight (Phytophthora infestans) 
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to 25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly. 
Critical Fungicide Management Notice (New Integration)
Mixtures of QoI-sensitive and QoI-resistant Alternaria populations were detected in aerial spore samples. The G143A mutation, which confers complete resistance to QoI (FRAC Group 11) fungicides, was identified in spore trap samples collected from potato fields in St. Johns and Putnam Counties between March 5 and April 9, 2026, as well as in samples collected during the March–April 2025 sampling period. QoI fungicides azoxystrobin-based products (e.g., Quadris, Satori, and Equation), fenamidone (Reason 500 SC), and pyraclostrobin (Cabrio EG and Headline 2.09 F). Due to the presence of resistant populations and the known cross-resistance among all FRAC Group 11 fungicides, these products are recommended to be applied in mixtures with fungicides of different modes of action to maintain effective disease control. While QoI fungicides may still provide some level of control, their use as standalone applications can increase the frequency of resistant populations, making mixture strategies necessary. Moreover, common SDHI resistance mutations (H277R, H278R, and H133R) were not detected in the analyzed samples. Review the Fungicide Application Guide for full details on resistance management: FRAC Group 11: QoI Fungicides and FRAC Group 3: SDHI Fungicides. In addition, consult the Vegetable Production Handbook in Florida for recommended fungicides mixtures and application programs.
POTATO SPORE REPORT
|
Pathogen |
Disease |
Visual Risk Alert/ Detection Summary |
|
|
Alternaria solani, |
Early blight, |
🔴
|
Detected in all traps at St Johns and Putnam Counties
|
|
Phytophthora infestans |
Late blight |
🟢 |
Not detected in all traps at St Johns and Putnam Counties
|
Spore Report Alert System  
🔴 Spores detected, indicating a potential disease risk, close monitor the field.
🟢  No spores detected, indicating no immediate concern.
Spore presence = potential, not guarantee. Combine spore data with crop stage, cultivar susceptibility, local weather, and fungicide resistance data to guide your actions.
Early blight and brown spot fungal spores were detected in both passive and active spore traps, including rotorods, Yroot samplers, and volumetric cyclone samplers strategically placed in potato fields at the UF-IFAS Hastings Agricultural Education Center (HAEC) as well as in commercial fields in St. Johns and Putnam Counties. These pathogens were also detected using a Burkard volumetric spore trap at the UF-IFAS HAEC station. The presence of airborne spores indicates a potential risk for disease development when environmental conditions become favorable. In contrast, spores associated with late blight were not detected across all traps during the sampling period, suggesting no immediate risk of late blight at this time.
The detection of fungal spores highlights the importance of proactive field monitoring and data-driven decision-making for effective disease management. Growers are encouraged to remain vigilant and adjust their management strategies, accordingly, using spore monitoring reports together with current weather conditions to help reduce potential disease risks.
In addition, monitoring of airborne Alternaria spores using a 7-day volumetric Burkard spore trap showed that spore concentrations were generally low during nighttime hours between 6:00 PM to 5:00 AM but increased significantly in the early morning. The highest spore levels were consistently detected between 6:00 AM and 12:00 noon, after which concentrations gradually declined toward the afternoon between 1:00 PM to 5:00 PM. These results indicate that the morning period represents the peak time for Alternaria spore dispersal.
Based on these observations, growers are encouraged to consider early morning fungicide applications (approximately 7:00–10:00 AM) when spore release is high and temperatures remain moderate, which may help improve spray coverage before foliage dries rapidly later in the day.
Environmental Conditions Favoring Disease Development 
Early Blight (Alternaria solani) 
Spore germination and infection primarily occur under favorable temperatures range of 68–86°F (20 to 26°C), high humidity, and extended leaf wetness. Frequent dew formation, overhead irrigation, fog, poor airflow, and rainfall increase disease risk.  
Brown Spot (Alternaria alternata) 
Long dew periods, humid environments, and temperatures between 64- 86°F (18 to 30°C) are favorable for spore germination and penetration. Disease severity increases with frequent wet-dry cycles, especially when rainfall or irrigation prolongs leaf surface moisture.  
Late Blight (Phytophthora infestans) 
The pathogen favors cool to moderate temperatures ranging from 50–75°F (10 to 25°C) with high relative humidity (≥90%) or leaf wetness periods exceeding 10 hours. Risk increases during cool nights with dew, fog, or persistent moisture. Sporangia, as inoculum, are easily dispersed by wind and wind-driven rain, facilitating the disease to spread rapidly. 
Critical Fungicide Management Notice (New Integration)
Mixtures of QoI-sensitive and QoI-resistant Alternaria populations were detected in aerial spore samples. The G143A mutation, which confers complete resistance to QoI (FRAC Group 11) fungicides, was identified in spore trap samples collected from potato fields in St. Johns and Putnam Counties between March 5 and April 16, 2026, as well as in samples collected during the March–April 2025 sampling period. QoI fungicides azoxystrobin-based products (e.g., Quadris, Satori, and Equation), fenamidone (Reason 500 SC), and pyraclostrobin (Cabrio EG and Headline 2.09 F). Due to the presence of resistant populations and the known cross-resistance among all FRAC Group 11 fungicides, these products are recommended to be applied in mixtures with fungicides of different modes of action to maintain effective disease control. While QoI fungicides may still provide some level of control, their use as standalone applications can increase the frequency of resistant populations, making mixture strategies necessary. Moreover, common SDHI resistance mutations (H277R, H278R, and H133R) were not detected in the analyzed samples. Review the Fungicide Application Guide for full details on resistance management: FRAC Group 11: QoI Fungicides and FRAC Group 3: SDHI Fungicides. In addition, consult the Vegetable Production Handbook in Florida for recommended fungicide mixtures and application programs.