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BIG DEFENCE Understanding Environmental Factors Leading to the Rise of Downy Mildew

Downy mildew, caused by the pathogen Plasmopara halstedii, typically thrives under specific environmental conditions. While the exact conditions may vary slightly depending on factors such as geographical location and crop variety, several key factors contribute to the development and spread of downy mildew:


  1. High Humidity: Relative humidity above 85% for an extended period provides an optimal environment for the pathogen to thrive.
  2. Moderate Temperatures: Moderate temperatures ranging from 15 to 25 degrees Celsius (59 to 77 degrees Fahrenheit) are conducive to downy mildew development. Temperatures outside this range can either inhibit or slow down the disease progression.
  3. Moisture on Plant Surfaces: Moisture on plant surfaces, such as dew or rainfall, creates favourable conditions for downy mildew spores to germinate and infect susceptible host plants. 
  4. Susceptible Host Plants: Downy mildew primarily affects plants within the Asteraceae family, with sunflowers being one of the most susceptible crops. 
  5. Wind Dispersal: Downy mildew spores are relatively small and lightweight, (they typically range in size from about 5 to 20 micrometers (µm) in diameter, allowing them to remain airborne for extended periods, particularly during weather events such as storms or atmospheric disturbances. Infected plant debris, neighbouring crops, or nearby fields can serve as sources of inoculum, facilitating the disease’s spread within and between fields.
  6. Susceptible Growth Stages: Young seedlings and plants during early vegetative stages are particularly susceptible to severe damage from the disease.

Understanding these specific conditions for downy mildew can aid growers in implementing effective disease management strategies, such as monitoring weather forecasts and implementing practices to reduce moisture accumulation. Early detection and prompt action are essential for mitigating the impact of downy mildew on crop yields. 


Using downy mildew-resistant hybrids widely regarded as one of the most effective and sustainable methods for managing the disease. This offers a holistic and sustainable approach to disease management, providing growers with effective protection against this devastating pathogen while promoting economic stability and environmental stewardship in agricultural systems.


Nuseed hybrids are bred with the highest levels of downy mildew resistance available. You can choose a sunflower hybrid with advanced resistance or one which matures up to 2 weeks early to provide flexibility on planting and harvest timing to avoid the environmental conditions conducive to downy mildew in your region.


N4H202 E

A high yield, guaranteed.

EU_N4H202 E


N4H202 E is a very stable high oleic hybrid that maintains good health all season long. It offers advanced resistance to downy mildew and is tolerant to ExpressSun® herbicide. This combination helps reduce risks for growers while maximising field productivity.

Downy mildew disease resistance rating 9


N4L215 E

Early harvest provides flexibility to the grower.

EU_N4L215 E


N4L215 E is our new linoleic hybrid that excels in various regions. Its early harvest gives growers extra time to prepare for winter crops, avoid drought conditions, or plant later. With excellent downy mildew resistance and ExpressSun® herbicide tolerance, N4L215 E reliably delivers high yields with low inputs.

Downy mildew disease resistance rating 9