Cultivation/Production, Most viewed stories, News July 2024, North America, Pests and Diseases

Urgent late blight alert: Ontario potato growers urged to act now to protect crops

Dr. Eugenia Banks, a leading potato specialist at the Ontario Potato Board, has issued an urgent alert to potato growers following the detection of late blight in a FL 2137 potato variety field in the Alliston area. This announcement comes after the grower initiated a robust response, deploying a tank mix of late blight-specific fungicides to curb the spread of the disease.

In her newsletter to subscribers, Dr. Banks emphasized the critical need for vigilance, advising growers to actively scout their fields and apply late blight-specific fungicides immediately. “Do not wait for the disease to infect your fields,” she warned. “The weather is providing excellent conditions for late blight development.”

She also noted that a comprehensive provincial strategy to mitigate the risk of a late blight epidemic is being collaboratively developed by WD Potato Ltd., the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), and the Ontario Potato Board.

Insights from the 2023 Late Blight Outbreak

To support her recommendations, Dr. Banks included a detailed presentation by Mark VanOostrum of WD Potato Ltd., presented at the Ontario Potato Board conference in February 2024. This presentation, which is available in this PDF, provides critical lessons from the severe late blight outbreak that devastated Ontario potato fields in 2023.

Key Takeaways from 2023:

Early Detection and Communication: The outbreak in 2023 was notable for its rapid spread, with the first official case confirmed on July 17th. Despite early dry conditions, a sudden period of rainfall in July facilitated the spread of the disease. Spore traps, positioned close to fields, failed to provide early warnings, underscoring the importance of continuous field scouting and timely communication among growers.

Impact on Yield and Quality: The outbreak led to significant crop losses and quality issues. Yields ranged from 230 to 450 cwt per acre, with early top-killed fields experiencing a shrinkage rate of 12-18%, compared to the normal 4%. The financial impact was also severe, with fungicide costs increasing by 40-60% and labor costs rising by 10-20%.

Management Practices: VanOostrum highlighted several effective management strategies, including the application of Phos Acid and Orondis fungicides, which were crucial in limiting the outbreak. The “spray often, spray early” mantra emerged as a vital approach to disease prevention. Proper harvest management and maintaining optimal pulp temperatures (52-66°F) post-harvest were essential in reducing rot incidence and preserving potato quality.

Success Stories: The presentation included case studies demonstrating the success of various strategies. One notable example involved an early topkill strategy that prevented disease spread in a late blight-tolerant variety. Another success story highlighted the importance of post-harvest acid applications in significantly reducing disease spread and breakdown in storage.

Read Mark VanOostrum’s full presentation as a pdf file here.

Looking Ahead: Strategies for 2024

In light of these insights, Dr. Banks’ newsletter urges growers to adopt a proactive approach. Immediate field scouting and the application of targeted fungicides are critical steps to protect this year’s crop. The provincial strategy being developed aims to provide growers with a robust framework for managing late blight and preventing a repeat of the 2023 outbreak.

Dr. Banks asks growers to “stay informed, stay proactive, and together we can safeguard Ontario’s potato fields from the threat of late blight”.

Source: Dr. Eugenia Banks
Image: Dreamstime Open Access Government

Editor & Publisher: Lukie Pieterse

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