The benefits of using a fungicide in a dry season

Written by Allison Hebert on Jun 12 2017

When there has been an abundance of rainfall in a season, applying a fungicide is second nature. In seasons where rain events are few and far between, fungicides can still deliver benefits to your crop.

A fungicide’s main purpose is to protect a plant from being infected with a disease or to reduce the spread of the disease within the plant.  Diseases are one of the biggest contributors to yield loss and grade reduction in grain.  In moist years, fungicide is a simple decision; high moisture means bigger yield but more chance of disease spreading throughout the crop.  However, there are benefits to fungicide, even in a dry year.

Increased Water Use Efficiency

A plant becomes stressed when there is a lack of moisture which kick-starts their defense mechanisms.  Defense mechanisms of plants include:

  • Premature ethylene production.
    • Ethylene is a chemical naturally produced by plants at many stages of life, typically when maturity and ripening occurs.
    • Ethylene is naturally produced by plants at many stages of life, typically when maturity and ripening occurs.
    • This causes the plant to limit unnecessary energy draws such as the development of new buds, flowers or pods.
  • The plant directing its energy to only a few pods to ensure the survival of the seeds for reproduction. 

Applying a fungicide will help a plant overcome drought and heat stress through reducing the amount of ethylene produced and increasing its water use efficiency.  When a plant is more effective at using the available water, it stays cooler and keeps the plant from shutting down and aborting pods. 

Increased Nutritional Capacity

Some of the growers I work with near Lethbridge did a dry-year fungicide trial in 2015 when moisture levels were well below average.  These growers were interested to see what kind of impact a fungicide application would have on a pea crop with little to no disease pressure and very dry conditions.  Trial results showed not only a yield increase but peas with a better harvestability and larger root mass. 

Fungicide applications reduced moisture stress on the plant.  This allowed the plant to put more energy into building a larger root system, which in turn enabled the uptake of moisture and vital nutrients.  At the end of the trial, some producers claimed up to an eight bushel per acre increase in yield where they used a fungicide on their peas, compared to where they did not.  That experience opened a lot of eyes on the impact a fungicide can have on a drought-stressed crop. 

A fungicide helps a plant grow to its full potential so it does not dry down before it has the chance to fill seeds properly.   They have also shown to increase root biomass which is important in dry conditions.  The more robust the roots, the better they are to seek moisture and vital nutrients.

Not all diseases spread through rainfall

In addition to general plant health benefits during dry conditions, there is still the potential for the spread of disease in these situations.  While it is true that most diseases require higher moisture levels, humidity and rainfall to help spread disease through the crop canopy, they may not need as much moisture as we think. 

  • A closed canopy will have a higher humidity level even if it hasn’t rained in a few days and the small amount of dew on the plants in the morning is enough to create the perfect environment for disease. 
  • There are some diseases such as Powdery Mildew, that will actually break down when there is high rainfall.  Fusarium Head Blight spores can be distributed with the wind as well as rainfall and only requires high humidity to become activated.   

If yield growth is your goal, fungicide can be a tool to help your crops perform at their best. It’s important to remember that crop canopies can trap disease, and fungicide can help plants reach their full potential. For local advice on disease pressure, crop conditions, or making a decision on fungicide, contact your Cargill Agronomist.

Tags: fungicide, Canola, drought stress

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