Potato Blight Resistance Crisis: How to Optimize Fungicide Strategies to Protect Crop Yields

Potato late blight (Phytophthora infestans) remains one of the most destructive diseases in agriculture, causing significant yield losses worldwide. Recently, a new strain, 43_A1, has been detected in Europe, showing resistance to carboxylic acid amide (CAA) fungicides, including mandipropamide (e.g., Revus). According to Pierre Deroo, a potato disease specialist at Arvalis, this strain was first identified in Denmark, leading to major efficacy losses, before spreading to the Benelux region and now France.

Current Resistance Trends in Europe

• In 2023, less than 10% of blight samples in Hauts-de-France contained the resistant strain.
• By 2024, this proportion surged to 17%, as reported by INRAE and Arvalis monitoring networks.
• Similar resistance concerns exist for oxathiapiproline (Zorvec), though at lower levels.

This follows historical patterns where overuse of single-mode fungicides led to resistance, such as with fluazinam and metalaxyl. Without intervention, 43_A1 could further reduce fungicide effectiveness, increasing production risks.

Key Strategies to Combat Resistance

1. Alternate Fungicide Modes of Action (MoA) – Avoid consecutive applications of the same chemical group.
2. Preventive Applications – Apply treatments before infection pressure peaks.
3. Integrated Pest Management (IPM) – Combine biological controls, resistant varieties, and cultural practices.
4. Monitoring & Testing – Regular field scouting and lab analyses help detect resistance early.

The spread of fungicide-resistant blight strains demands urgent action. Farmers and agronomists must diversify chemical treatments, adopt IPM strategies, and stay informed through surveillance networks. Proactive resistance management is critical to sustaining potato yields and protecting food security.