I’m continuing my series on organic vs conventional food production and the importance of soil health. In this blog, let’s consider the importance of the use of fungicides.

In the quest to produce abundant, healthy food, farmers face numerous challenges, one of the most significant being plant diseases caused by fungi. This is where fungicides come into play. Understanding why we use fungicides and their role in both organic and conventional farming is crucial to appreciating the complexities of modern agriculture.

Fungi are ubiquitous in the environment and can pose severe threats to crops. Fungal diseases such as rusts, blights, and mildews can devastate yields, affecting the quality and quantity of food produced. These diseases not only reduce crop productivity but can also render produce unsellable, leading to significant economic losses for farmers.

Here in Colorado, we grow a lot of potatoes. In the past, before the advent of modern fungicides, entire crops could be lost to fungal outbreaks. The infamous Irish Potato Famine in the 1840s, caused by the fungal pathogen Phytophthora infestans, is a stark historical example of the devastating impact of fungal diseases on food security. This tragedy highlighted the importance of disease-resistant crops and effective disease management strategies.

When it comes to growing potatoes, the risk of disease is particularly high. Seed potatoes, which are specially grown to be free of disease, must be used instead of non-seed potatoes to mitigate this risk. Using non-seed potatoes, such as those bought for consumption from grocery stores, can introduce pathogens into the soil, leading to crop failure and the spread of diseases like late blight, which was responsible for the Irish Potato Famine. Seed potatoes are certified disease-free and are crucial for ensuring a healthy and productive potato crop.

Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. They work in various ways:

1. Preventative Fungicides: These are applied before the onset of disease. They create a protective barrier on the plant surface, preventing fungal spores from germinating and infecting the plant.

2. Curative Fungicides: These are used after the disease has started to develop. They target the fungal infection within the plant tissues, stopping its spread and minimizing damage.

3. Eradicative Fungicides: These aim to eliminate the fungal pathogen entirely, often used when an outbreak has occurred to clear up the infection and prevent further spread.

Fungicides in Conventional Farming

In conventional farming, synthetic fungicides are commonly used due to their effectiveness and reliability. These fungicides are developed through extensive research and testing to ensure they target specific fungi without causing undue harm to the crops or the environment. Some common synthetic fungicides include azoxystrobin, chlorothalonil, and mancozeb.

Conventional farmers rely on these fungicides to protect their crops, ensuring stable yields and consistent food supply. The use of fungicides allows for large-scale monoculture farming, which, while efficient, can be more susceptible to fungal diseases due to the genetic uniformity of the crops.

Fungicides in Organic Farming

Organic farming takes a different approach to disease management. While synthetic fungicides are generally prohibited, organic farmers use natural or non-synthetic alternatives. These include:

1. Copper-based Fungicides: Copper compounds, such as copper sulfate, are used to control a broad spectrum of fungal diseases. However, their use is regulated due to potential environmental impacts.

2. Sulfur-based Fungicides: Elemental sulfur is another widely used fungicide in organic farming, effective against many fungal pathogens.

3. Biological Fungicides: These include beneficial microorganisms that outcompete or inhibit the growth of harmful fungi. Trichoderma and Bacillus species are examples of biological fungicides used in organic systems.

Organic farmers also rely heavily on cultural practices to manage fungal diseases. Crop rotation, selecting disease-resistant varieties, and improving soil health are all strategies used to minimize the occurrence of fungal infections.

If you have a lawn, you may have experienced leaf blight, a common fungal disease in Kentucky bluegrass. Ascochyta leaf blight is particularly prevalent in the summer when bluegrass becomes heat-stressed. This fungus spreads through the wind and can hitch a ride on lawnmower wheels, making it easily transmissible. Leaf blight primarily affects the upper leaf blade of the grass, causing it to die off, but typically does not harm the root system. With proper management, the grass can recover over time, as the fungus can be controlled and the grass can regrow healthy leaves.

In my next blog, we’ll discuss herbicides and the options for organic growers to control weeds.

The Role of Fungicides in Food Production

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